Abstracts and Intra-symposium Fieldtrip

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1 Abstracts and Intra-symposium Fieldtrip 1

2 PREVIOUS MEETINGS Primera Reunión Argentina de Icnología (Santa Rosa, 1993) Segunda Reunión Argentina de Icnología (San Juan, 1995) Tercera Reunión Argentina de Icnología and Primera Reunión de Icnología del Mercosur (Mar del Plata, 1998) Cuarta Reunión Argentina de Icnología and Segunda Reunión de Icnología del Mercosur (San Miguel de Tucumán, 2001) Quinta Reunión Argentina de Icnología and Tercera Reunión de Icnología del Mercosur (Ushuaia, 2007) Simposio Latinoamericano de Icnología SLIC2010 (São Leopoldo, 2010)

3 SLIC 2013 SECOND LATIN AMERICAN SYMPOSIUM ON ICHNOLOGY Abstracts and Intra-Symposium Fieldtrip September 16-20, 2013 INCITAP (CONICET-UNLPam) Universidad Nacional de La Pampa (UNLPam) Scientific Committe Luis A. Buatois, María Gabriela Mángano, Renata Netto, Marcelo A. Zárate Editors Emilio Bedatou, Renata Sostillo, Julio A. Varela

4 SLIC2013 Second Latin American Symposium on Ichnology SLIC SECOND LATIN AMERICAN SYMPOSIUM ON ICHNOLOGY President: Ricardo N. Melchor (UNLPam CONICET, Argentina) Vicepresident: Ismar de Souza Carvalho (Universidad Federal do Rio de Janeiro, Brasil) Past-president: Renata Netto (UNISINOS, Brasil) Secretary: Emilio Bedatou (UNLPam CONICET, Argentina) Treasurer: Aldo M. Umazano (UNLPam, Argentina) Vocals: Eduardo S. Bellosi (Museo Argentino de Ciencias Naturales CONICET, Argentina), Mariano Verde Cataldo (Facultad de Ciencias, Uruguay), María C. Cardonatto (UNLPam, Argentina), Mirta G. González (Museo Argentino de Ciencias Naturales CONICET, Argentina), Javier M. Krause (Museo Egidio Feruglio CONICET, Argentina), Claudia I. Montalvo (UNLPam, Argentina), María V. Sánchez (Museo Argentino de Ciencias Naturales CONICET, Argentina), Laura C. Sarzetti (Museo Argentino de Ciencias Naturales CONICET, Argentina), Renata Sostillo (UNLPam CONICET, Argentina), Julio A. Varela (UNLPam CONICET, Argentina), Mariano Perez (UNLPam CONICET, Argentina). Scientific Committe: Luis A. Buatois (University of Saskatchewan, Canadá) María Gabriela Mángano (University of Saskatchewan, Canadá) Renata Netto (UNISINOS, Brasil) Marcelo A. Zárate (INCITAP Universidad Nacional de La Pampa, Argentina) Sponsors: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) Universidad Nacional de La Pampa (UNLPam) Instituto de Ciencias de la Tierra y Ambientales de La Pampa (INCITAP) Consejo Profesional de Ciencias Naturales (COPROCNA) Gobierno de La Pampa Fundación Banco de La Pampa International Association of Sedimentologists (IAS) International Ichnological Association (IIA) Asociación Geológica Argentina (AGA) Asociación Argentina de Sedimentología (AAS) Asociación Paleontológica Argentina (APA) Cover photo Close-up of isolated right pes impression (natural mold) of Batrachichnus salamandroides (amphibian footprint) from the Permian Carapacha Formation, La Pampa province, Argentina. The footprint is 16 mm long. 4

5 Abstracts and Intra-symposium Fieldtrip INDEX Conferences De Valais, S. Small early mammals in the shadow of Jurassic dinosaurs: La Matilde ichnofauna, Patagonia...13 Loope, D. Signs of life in ancient dune fields...14 Mcllroy, D. Did bioturbating ecosystem engineers fuel the Cambrian explosion?...15 Netto, R.G. Ichnology of sandy beaches: lessons from the South Atlantic Brazilian coast...16 Nicosia, U. Italy: a sea-side dinosaur resort...17 Parras, A. Sclerobiont communities associated to oysters and pectinids during the Oligocene/ Miocene in southern Patagonia...18 Pazos, P.J. Ichnology: sedimentologic and stratigraphic applications to the study of the Lower Cretaceous of the Neuquén Basin...19 Poiré, D.G. Ichnostatistics applied to sedimentary models and oil basin analysis...20 Abstracts Aceñolaza, G., Bayetgoll, A., Nieva, S. and Aráoz, L. Environmental constraints of a Middle Ordovician trace fossil association from the Lina Formation (Puna of Jujuy province, NW Argentina)...23 Árpád, D. and Apró, A. Bioeroded bone fragments from the late Miocene of Hungary...24 Árpád, D, Torba, K and Fodor, R. Evidences of arthropod-plant interactions on early Oligocene leaves...25 Bayetgoll, A., Aceñolaza, G., Moussavi-Harami, R. and Mahboubi, A. Trace fossils and environments of the Shirgesht Formation (Ordovician of Kamard, central Iran)...26 Bellosi, E.S., Krause J.M. and Bedatou, E. Digging into paleosol - trace fossil relationships

6 SLIC2013 Second Latin American Symposium on Ichnology Brezina, S.S., Romero, M.V. and Casadío, S. Boring and encrusting barnacles through the Cretaceous/Paleogene boundary in northern Patagonia (Argentina)...28 Buatois, L.A. and Mángano, M.G. Ichnologic insights into the early colonization of the deep sea...29 Canale, N., Ponce, J.J., Carmona, N.B. and Drittanti, D. Caracterización icnológica de sistemas de barras deltaicas de la Formación Lajas en la Sierra de la Vaca Muerta (Jurásico Medio), Cuenca Neuquina, Argentina...30 Carmona, N.B., Ponce, J.J., Wetzel, A., Bournod, C. and Cuadrado, D. Paleoenvironmental implications of resting, locomotion and equilibrium/escape structures of freshwater bivalves, Río Negro Formation (late Miocene-early Pliocene)...31 Carvalho, I.S. and Borghi, L. Microbial mats and the preservation of the invertebrate tracefossils from the Sousa basin (Early Cretaceous), Brazil...32 Cereceda, A., Poiré, D.G., Richiano, S. and Varela, A.N. Primeras aproximaciones en la caracterización icnológica de la Formación Alta Vista: implicancias paleoambientales...33 Cónsole-Gonella, C., de Valais, S., Sánchez, M.C., Marquillas, R.A. and Herrera Oviedo, P. Icnocenosis de vertebrados e invertebrados en el Subgrupo Balbuena (Maastrichtiano-Daniano), Quebrada de Humahuaca, noroeste argentino...34 Dentzien Dias, P.C. and Quezado de Figueiredo, A.E. Burrow architecture and burrowing dynamics of Ctenomys sp. in southern Brazil foredunes...35 Dobler Lima, J.H. and Guimarães Netto, R. Ichnology of deglaciation deposits of the Taciba Formation (Upper Carboniferous/Lower Permian, Paraná Basin) at Santa Catarina State (S Brazil)...36 Farinati, E.A., Aguirre, M.L. and Richiano, S. Bioerosión en Crepidula (Mollusca, Gastropoda) del Cuaternario marino de Argentina: interacciones bióticas con poliquetos (Annelida, Spionidae)...37 Fernández, D.E. and Pazos, P.J. Ichnological study of the Lower Cretaceous Mulichinco Formation (Neuquén Basin, northern Patagonia): preliminary results...38 Fernández, D.E., Pazos, P.J., Pérez, D.E. and Luci, L. Asteroid trace fossils from a Lower Cretaceous shallow marine paleoenvironment in Patagonia: the first record of starfishes for the Agrio Formation

7 Abstracts and Intra-symposium Fieldtrip Fodor, R. Occurrence of small Ophiomorpha from various early Miocene formations of Hungary...40 Gomes Barroso, F.R., Sales Viana, M.S., Agostinho, S. and Ferreira De Lima Filho, M. Icnofósseis associados à fauna de Ediacara da Bacia do Jaibaras (Nordeste do Brasil)...41 Kihn, R.G. and Gómez, E.A. Bioerosión en ostrácodos de sedimentos holocenos del estuario de Bahía Blanca...42 Macias, C., Moreno, K. and Pino, M. Una icnita humana del Pleistoceno tardío, Sitio Arqueopaleontológico Pilauco, Región de Los Lagos, Osorno, Chile...43 Mángano, M.G. and Buatois, L.A. Tidal flats through time: the trace-fossil record of evolutionary innovations and faunal turnover...44 Marchetti, L., Avanzini, M., Conti, M.A. and Santi, G. Early Permian vertebrate ichnology of the Southern Alps (N Italy): new discoveries and sites of interest...45 Marchetti, L., Ronchi, A. and Santi, G. The Early Permian Gerola Valley ichnosite (W Orobic Basin, N Italy): taxonomical revision and paleoenvironmental reconstruction...46 Melchor, R.N., Cardonatto, M.C. and Tickyj H. Diverse deep marine trace fossils from the Early Paleozoic metasediments of the Las Lagunitas Formation, Frontal Cordillera, Argentina...47 Mikuś, P. and Uchman, A. Beetle burrows with a terminal chamber across a modern river valley: an example from the southern Poland...48 Moreno Sánchez, M. and Gómez-Cruz, A. de J. Huellas de dinosaurios en Colombia: revisión y nuevos hallazgos...49 Muñiz, F., Cáceres, L.M., Rodríguez-Vidal, J., Finlayson, C., Fa, D., Finlayson, G., Abad, M. and Ruiz, F. Huellas de vertebrados en dunas costeras del Pleistoceno superior de Gibraltar (S de la Península Ibérica)...50 Muñiz, F., Cárcamo, C., Belaústegui, Z., Domènech, R. and Martinell, J. Trazas cruzianiformes producidas por espáridos actuales en el Estuario del Río Piedras (Lepe, Huelva, SO España)...51 Oliva, C., Arregui, M., Lirusso, V. and de Valais, S. Laguna del Monte, un nuevo yacimiento paleoicnológico del Pleistoceno tardío (Piso/Edad Lujanense), Guaminí, provincia de Buenos Aires (Argentina)

8 SLIC2013 Second Latin American Symposium on Ichnology Paes Neto, V.D., Pretto, F.A., Quezado de Figueiredo, A., Francischini, H., Soares, M.B. and Schultz, C.L. Insect trace fossils on Middle and Late Triassic vertebrate bones: ancient dermestid and termite activity?...53 Paes Neto, V.D., Pretto, F.A., Quezado de Figueiredo, A.E., Soares, M.B. and Schultz, C.L. A new occurrence of archosaur tooth marks on Late Triassic bones from southernmost Brazil...54 Pazos, P.J., Heredia, A. and Cingolani, C. The Nereites ichnofacies in the lower Paleozoic Río Seco de los Castaños Formation, Mendoza, Argentina: age, facies and trace-fossil content...55 Pazos, P.J., Rusconi, F. and Gutiérrez, C. Zoophycos in fluvial facies of the El Imperial Formation (Pennsylvanian/Cisuralian) of the San Rafael Basin: the record of an overlooked transgression...56 Pérez, M., Umazano, A.M. and Melchor, R.N. Cretaceous burrows of probable vertebrate origin from volcaniclastic interdune deposits of the Cerro Barcino Formation, Patagonia, Argentina...57 Pérez, M., Umazano, A.M. and Melchor, R.N. Early Cretaceous ichnofauna from eolian and associated deposits of Patagonia: the Cerro Barcino Formation, Chubut, Argentina...58 Pineda-Salgado, G., Quiroz-Barroso, A.S. and Sour-Tovar, F. Estudio icnológico de los clastos de una playa rocosa del Mioceno, Formación Concepción, Veracruz, México...59 Quezado de Figueiredo, A.E., Dentzien-Dias, P.C. and Schultz, C.L. Inclusões de Dipnoi em coprolitos, Formação Rio do Rasto (Permiano Médio-Superior), Rio Grande do Sul, Brasil...60 Richiano, S. The Zoophycos Ichnofacies in the Río Mayer Formation (Austral Basin, Patagonia): palaeoenvironmental controls on its development...61 Richiano, S., Aguirre, M.L., Davies, K., Castellanos, I. and Farinatti, E. Characterization of bioerosion structures in marine Quaternary mollusks from Bahía Bustamante (Patagonia, Argentina): preliminary results...62 Richiano, S., Varela, A.N. and Poiré, D.G. Distribución de trazas fósiles en hemigrabenes: ejemplo en la Formación Springhill, Cuenca Austral, Patagonia, Argentina...63 Roland, G and Verde, M. Trazas meniscadas en ejemplares de Uruguay rivasi de la Formación Asencio (Eoceno temprano) de Uruguay...64 Roland, G. and Verde, M. Una nueva icnoespecie de nido de abejas del icnogénero Uruguay para la Formación Asencio (Eoceno temprano) de Uruguay

9 Abstracts and Intra-symposium Fieldtrip Sostillo, R., Cardonatto, M.C., Montalvo, C.I., Visconti, G. and Melchor, R.N. New findings of invertebrate trace fossils in a Late Miocene loess-paleosol succession, Cerro Azul Formation, La Pampa, Argentina...66 Varela, A.N., Richiano, S. and Poiré, D.G. Ichnology of the brackish water intervals of the Puesto El Moro Formation, Upper Cretaceous, Austral Basin, Argentina...67 Verde, M. Insect trace fossils diversity in ultisols and calcisols, and paleoclimatic oscillations during the Late Cretaceous to Paleogene in Uruguay...68 Verde, M., Ubilla, M. y Roland, G. Castrichnus n. isp., earthworm aestivation chambers in early Holocene paleosols from southern Uruguay...69 Vildoso Morales, C.A. and Sciammaro, M.P. Análisis preliminar de rastro de iguanodonte (Dinosauria, Ornithopoda) en el Cretácico Temprano de los Conchucos (Andes del Norte Peruano)...70 Vildoso Morales, C.A. and Sciammaro, M.P. Inferencias paleoambientales en torno a huellas de saurópodos (Dinosauria, Sauropodomorpha) en el Albiano de Yanashalla, Andes del Norte Peruano...71 Vilmova, E.S. Triassic deposits and ichnofossils of Transbaikalia (Russia)...72 Zapata, L., Krapovickas, V., Raigemborn, M.S. and Matheos, S.D. Presencia de icnofacies de Glossifungites en la base de la Formación Santa Cruz (Mioceno inferior-medio), sudeste de la provincia de Santa Cruz, Patagonia Austral...73 Intra-symposium fieldtrip Melchor, R.N., Visconti, G. and Montalvo, C.I. Late Miocene ant nests and associated ichnofossils from paleosols: The Cerro Azul Formation at Salinas Grandes de Hidalgo, La Pampa, Argentina

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13 Abstracts and Intra-symposium Fieldtrip Small early mammals in the shadow of Jurassic dinosaurs: La Matilde ichnofauna, Patagonia de Valais, S. CONICET-Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, General Roca, Río Negro, Argentina, [email protected] The Middle Jurassic vertebrate track record from the world is relatively scarce. In South America, tetrapod tracks are restricted to two localities, both in the Argentinean Patagonia. The first site has yielded up to now only one tridactyl isolated, probably a theropod track, from the Cañadón Asfalto Formation, Cerro Cóndor locality, Chubut Province. The second one is the extraordinary ichnofossiliferous locality at the Estancia Laguna Manantiales, from the La Matilde Formation, 25 km to the northwest of the Jaramillo Petrified Forest National Park Office, Santa Cruz Province. The La Matilde Formation covers an area of approximately km 2 in the Santa Cruz Province, and overlies and interdigitates with the Chon Aike Formation, comprising some authors also include to the Bajo Pobre Formation the Bahía Laura Group. The unit is covered in angular discordance by the Baqueró Group (Aptian). The formation has been dated on the basis on its paleofauna and paleoflora record, as well as radiometric dating of volcanics from the Chon Aike Formation, which constrain the age to the Ma interval (Bajocian-Callovian; Late Middle Jurassic). The analyzed section includes primary and reworked siliceous volcaniclastic sediments, mainly tuffs, lapilli-stone, tuffaceous sandstones, and rare ignimbrites and breccias. The earliest ichnological studies in the Laguna Manantiales site were carried out by Dr. Rodolfo Casamiquela and Argentinean colleagues, when they found the first track-bearing level. Originally, the tracks were named as four ichnotaxa, although at the present time, the panorama has changed: 1) Ameghinichnus Casamiquela, 1961, quadrupedal trackway, homopod, pentadactyl pes and manus, assigned to basal mammals. In the beginning, all the specimens were included in A. patagonicus Casamiquela, 1961, but a group of track was different enough to deserve a separate designation, A. manantialensis de Valais, 2009; 2) Delatorrichnus goyenechei Casamiquela, 1964, endemic, with the manus impressions nearly rhomboid in outline, with up to four digits, and tridactyl pes prints, related to obligate quadrupedal ornithisquian dinosaur; 3) Sarmientichnus scagliai Casamiquela, 1964, endemic, functionally didactyl tracks, with impressions of digits I and III forming a single, linear depression, assigned to a medium-sized theropod dinosaur. Then, a new ichnotaxa was erected, Casamiquelichnus navesorum Coria y Carabajal, 2004, now considered a junior synonym of S. scagliai; 4) Wildeichnus navesi Casamiquela, 1964, tridactyl tracks, with a wide total divarication, attributed to a small-sized theropod; 5) Grallator Hitchcock, 1958, footprints similar to Wildeichnus but with narrow total divarication, assigned to small-sized theropods; 6) two isolated and incomplete footprints, lacking morphological details to make an ichnotaxonomical assignment; 7) the ichnological record is completed by abundant invertebrates traces assigned to Hexapodichnus casamiquelai de Valais et al., 2003 and some specimens of Lithographus hieroglyphicus Hitchcock, 1858, both related to pterygote insects, as well as specimens of Helmintoidichnites tenuis Fitch, 1850, Diplichnites isp., usually assigned to myriapods, and root traces. Three track-bearing levels have been recognized. The basal level, 9.2 m to the basis of the local section, contains the four ichnogenera named by Casamiquela. The second level, 16.3 m of the basis, has preserved Delatorrichnus and Ameghinichnus. The upper level, to 50 m of the basis, associated to a paleosol with an in situ araucarian stump, contains Ameghinichnus, Wildeichnus, Grallator, Sarmientichnus, and Hexapodichnus, besides the rest of the invertebrate ichnotaxa, root traces, and the indeterminate vertebrate tracks. Therefore, the La Matilde ichnofauna is characterized by having trace fossils assigned to small to medium-sized theropods, basal mammals, and arthropods, differing from the other Middle Jurassic Gondwanan ichnofaunas, usually represented by large-sized sauropod and theropod footprints. The paleoenvironment, interpreted as a fluvial system, with swamps and water bodies probably derived from adjacent floodplains associated to volcanic activity, explains the unusual features of the ichnofauna. This volcanic activity may have produced a selective pressure for the evolutive adaptation of the components of the paleocommunity towards forms of minor size. 13

14 SLIC2013 Second Latin American Symposium on Ichnology Signs of life in ancient dune fields Loope, D. Earth & Atmospheric Sciences, University of Nebraska, Lincoln, Life in active dune fields is seldom so prolific that all physical structures within the dunes are destroyed. Because wind-ripple laminae are thin, extensive, and distinct, the tracks and burrows of ancient dune dwellers that disrupt these strata are prominent. Grainflow strata (dry avalanches)are homogeneous and thick, so traces they contain show less detail.if plants are able to stabilize the dunes, they can trap copious dust, and thereby change the texture and chemistry of their substrate. Calcitecemented rhizoliths are common in Carboniferous to Recent eolian strata. In many cases rhizoliths develop parallel to cross-strata because, in the vadose zone, roots exploit water that is preferentially held in the finest laminae. Vertebrate tracks produced on active duneslopes are most easily seen in vertical cross-section. Tracks need not be emplaced in moist sand to be preserved. In dry grainflows, the uppermost parts of tracks are commonly sharply truncated by animal-induced avalanching, but the deformed strata that make up the bulk of the track are preserved. Large tetrapods moving across low-angle wind-ripple laminae can deform the substrate far beyond the lateral margins of the true track, generating a distinct zone of extensional faulting ahead of the true track, and a compressional, thrust-faulted zone in the rear.in the Lower Jurassic Navajo Sandstone, tracks of small theropod dinosaurs are abundant along faint cross-strata within rock that is nearly bioturbated by small burrows presumably made by insects. The association of tracks and burrows suggests a predatorprey relationship, but it also begs the question: What (and where) were the primary producers for the sand-sea ecosystem? In the thick, widespread dune deposit, the only evidence for vascular plants is petrified wood associated with interdune ponds near the top of the formation, and a few scattered rhizolith localities. Sheets of cohesive blocks that slumped down slipfaces suggest that monsoonal rains wetted the dune field seasonally. Could the microflora that grew within ephemeral ponds during the wet season have supplied the energy for the animal populations?in modern deserts, the surfaces of subtropical sand dunes can reach 80 C, and many animals escape the heat by burrowing during the day and emerging only at night. Although vertebrate bones are rarely found in eolian strata, the skeleton of a tritylodontidsynapsid from the Navajo Sandstone has been interpreted as that of a scratch digger. Within the Middle Jurassic Entrada Sandstone, burrows that are up to 60 cm in diameter and several meters in length, descend at ~20 from bounding surfaces, and cut underlying large-scale cross-strata. Some of these burrows are filled with brecciated blocks of wind-ripple strata, some are internally structureless, and the upper part of one contains small-scale cross-strata that prograded into the throat of the burrow. Non-biogenic structures in dune cross-strata can easily be confused with trace fossils. The high initial porosity of grainflows makes eolian cross-strata especially vulnerable to liquefaction. In cemented, Pliocene calcareous eolian sands on Mallorca, horizontal sections through the undertracks of goats are commonly circular, retaining no detail of foot structure. Circular features spatially associated with Jurassic tracks, and aligned in rows resembling trackways, are, however, best interpreted as cross-sections of water-escape pipes produced by liquefaction triggered by paleoearthquakes. At one site in the Navajo Sandstone, vertical pipes with conical tops repeatedly vented onto the lee slope of a large, migrating dune. Eight distinct generations of sand blows, separated by intervening wind-ripple laminae record a Jurassic earthquake sequence that lasted about one year. The trace fossils (and other forms of soft-sediment deformation) preserved in dune strata have received relatively little attention, and are deserving of much further study. 14

15 Abstracts and Intra-symposium Fieldtrip Did bioturbating ecosystem engineers fuel the Cambrian explosion? McIlroy, D. Department of Earth Sciences, Memorial University of Newfoundland, St John s, Since the definition of the Precambrian-Cambrian boundary at the base of the Treptichnus (Phycodes) pedum ichnozone-at the type section in southeastern Newfoundland-ichnological research has been a key part of the evidence for the early evolution of complex animal life. Study of the most complete stratigraphic successions worldwide has largely vindicated the usefulness of the boundary decision. That the base of the Phanerozoic can be defined on ichnological grounds also supports the inference that the advent of burrowing is in some way tied to the evolution of early animal life. This talk explores from a conceptual perspective the first order biogeochemical challenges that the earliest (Ediacaran) benthic macro-organisms would have experienced. 1) Why did macro-organisms first locomote?, 2) Why did they first burrow?, 3) What drove the adaptive (behavioural) evolution of burrowing styles? The biological controls on the evolution of the benthos are explored through consideration of the Precambrian to Cambrian transition in Newfoundland, Canada. Recent work has uncovered the earliest trace fossils (surface trails) from the Mistaken Point Formation of southeastern Newfoundland, and the trace fossil rich strata of the type sections of the Precambrian-Cambrian boundary allow us to track the evolution of complex burrowing strategies through the Fortunian stage of the Cambrian. The complete spectrum of fundamental behavioural styles that characterize the rest of the Phanerozoic are inferred to have been present at around the base of Cambrian Stage 2. Earlier work has suggested that the evolution of bioturbation was likely to have increased the microbial biomass of marine sediments, creating a positive feedback loop that is hypothesized to have fuelled the Cambrian Explosion of complex animal life. With the advent of pervasive bioturbation there is an increased supply of bio-limiting nutrients to the microbiota of the sediment, which in turn constitutes the food resource to sustain larger more efficient bioturbators. Modern understanding of the linkages between bioturbation and nutrient cycling allows refinement of this model. The first burrowing organisms are here considered to be ecosystem engineers- organisms that modify their environment through their life actions. The evolution of burrowing organisms was transformational in creating dynamic, strongly three dimensional (Phanerozoic-type) benthic environments from the pre-existing-essentially two dimensional-precambrian seafloor. This is considered to be ecosystem engineering on the grandest scale. 15

16 SLIC2013 Second Latin American Symposium on Ichnology Ichnology of sandy beaches: lessons from the South Atlantic Brazilian coast Netto, R.G. PPGeo, Universidade do Vale do Rio dos Sinos, São Leopoldo, Brazil, The circa 500 km-long Atlantic coast that characterizes the eastern border of the Rio Grande do Sul Sate, southern Brazil, has been providing relevant information about the ichnology of mid-latitude sandy beaches. The Rio Grande do Sul coastal plain are composed of four successive barrier-lagoon systems formed during highstand sea levels related to glacio-eustatic cycles during the Quaternary. The oldest systems (I t o III, Pleistocene) are located to the west, while the youngest are situated to the east (System IV, Holocene, representing the modern beach) as a result of coastal plain progradation. The dominance of sub-tropical, humid temperate climate inhibits carbonate precipitation and quartz grains up to mm in diameter are the main component (90-99%) of the deposits. The high energy of waves and the micro-tidal regime obliterate the shoreface exposure, while the foreshore and backshore settings are well exposed. Back-barrier deposits can be accessed locally, preferentially at Peixe Lagoon and Chuí Creek mouths. Mottling burrows produced by ophellid Euzonus furcifera and scolecid Scolepis gaucha polychaetes are common in 50-cm deep or more foreshore substrates and resemble Macaronichnus isp. Vertical shafts produced by burrowing bivalves (chiefly Donax hanleyanus) and tiny trackways of crustacean (Emerita brasiliensis), resembling Skolithos verticalis and Cruziana problematica, respectively, as well as insect (dominantly beetles) and bird trackways are also common in foreshore substrates. Cerianthid anemone resting traces (similar to Bergaueria hemisphaerica) and fecal pellets may rarely occur. In the ichnofossiliferous Pleistocene Barrier III deposits, however, only Macaronichnus isp. can be observed, as the potential of preservation of the epigenic structures and shallow burrows in such energetic foreshore is low. At the south of Patos Lagoon channel mouth, during low tide, is possible to observe a considerably high amount of chimneys that represent the openings of Sergio mirim (arthropod callianassid) burrow systems. The burrows extend to more than a meter deep into the substrate and show thick-walled burrow necks with narrow entrance, pelleted lining, dychotomic branching and pellet morphologies equivalent to those observed in Ophiomorpha nodosa preserved in Pleistocene Barrier III deposits. Fecal pellets, such as Tomaculum isp., can also be observed around the opening mounds, but are not preserved in the Pleistocene deposits, suggesting that they are carried out with currents to other settings. Backshore and back-barrier deposits show a moderate to high diversity and abundance of biogenic structures, but with low potential of preservation. Insect and vertebrates (birds, reptiles and mammals) trackways and burrows predominate in the whole area, but crab burrows are also common in the flat areas in front of the frontal dunes (Ocypode quadrata) and at lagoon edges (Neohelice granulata and Uca uruguayensis). Crab burrows show a higher potential of preservation than the other biogenic structures, resembling Psilonichnus isp. of variable size, the height depending on the groundwater level. The study of analogue burrows and their distribution in coastal settings is helping to evaluate better the Rio Grande do Sul coastal dynamics through the Quaternary, as well as to infer the relationship between the coastal processes and the biotic distribution along high-energy sandy beaches. 16

17 Abstracts and Intra-symposium Fieldtrip Italy: a seaside dinosaur resort Nicosia, U. Dipartimento di Scienze della Terra, Sapienza Università di Roma, Rome, Italy, [email protected] Dinosaurs from Italian deposits were practically unknown until a fortuitous discovery of footprints in Before, and for a long time, that situation was considered normal, since most of Mesozoic deposits of Italy are represented by marine sediments. Besides, in paleogeographic models, the different domains, which today constitute the Alps and the Apennines, were situated well inside the Tethys Ocean, a large Mesozoic seaway between Africa and Europe. After 1985 this situation changed dramatically, especially because of the finding of dinosaur tracks and trackways. At the, the number of dinosaur tracksites is surprisingly high and grows continuously. An annotated census of dinosaur life evidence (tracksites and few scattered bone remains) allowed to shed light upon the complex geodynamic history of this sector of the Central Mediterranean region, which so became a key area to understand the relationships between Laurasia and Gondwana during Mesozoic times, and their reciprocal movements. The Italian dinosaur track-bearing outcrops, almost all from carbonate platform environments (from intertidal to supratidal), have been subdivided into two groups, the first including the Triassic-Jurassic ichnosites and the second the Cretaceous ones. The ichnosite distribution shows a sharp partition between Triassic-Early Jurassic ichnoassociations, present only in Northern Italy, and Cretaceous ichnoassociations, mostly present in the peninsular Italy. The data suggest that, in the Southalpine domain, the Triassic-Early Jurassic fauna underwent a Pliensbachian local disappearance. During that age, the geodynamical controlled drowning of the carbonate platforms, along the northern margin of the opening Tethys, swept away dinosaurs determining the ultimate disappearance of environments suitable for their survival. The distribution of the Tithonian-Maastrichtian track-bearing outcrops is more complex and must be analyzed based on a further subdivision into two groups: the first one including the latest Jurassic mid Cretaceous sites, and the second concerning the latest Cretaceous ones. The presence of dinosaurs, during the late Tithonian-Cenomanian time interval, well after that these areas have been pulled apart from Laurasia (Early Jurassic rifting), has been explained by recurring immigration events from the northern Gondwana emerged lands to the existing carbonate platforms, throughout a filtering bridge. Subsequently (Santonian-Maastrichtian), the Apulian platform (one of the South Italy platforms) coalesced with the European archipelago allowing the end-cretaceous southward immigration of European paleobioprovince inhabitants. It seems parsimonious to infer that, after immigration phases, the lack of suitable environments led the immigrants to disappear from these areas shortly after their arrival. The peculiar environment characterizing the immigration areas probably repeatedly pushed dinosaurs to try a settling in these zones, possibly by means of shore dwelling pre-adaptation and the development of an opportunistic diet, though this has proved unsuccessful. The results of this research confirmed that paleontology is still a powerful tool in large scale paleogeography with dramatic repercussions even in regard to the currently accepted geodynamic models. Moreover, this work has been particularly rewarding for the Rome research group claiming a useful role within the great geology for vertebrate ichnologists. 17

18 SLIC2013 Second Latin American Symposium on Ichnology Sclerobiont communities associated to oysters and pectinids during the Oligocene/Miocene in southern Patagonia Parras, A. INCITAP (CONICET - Facultad de Ciencias Exactas y Naturales), UNLPam, Santa Rosa, La Pampa, Argentina, [email protected] Oysters and pectinids are calcitic mollusks that are among those with the highest chances of preservation. They also provide an excellent record of the associated sclerobiont communities. Rocks assigned to the San Julián, Monte León, Estancia 25 de Mayo, and Santa Cruz Formations (late Oligocene/early Miocene) exposed along the coast and western area of Santa Cruz Province (Patagonia, Argentina) carry an abundant fauna of these mollusks, offering an excellent opportunity to gain insight into the high-latitude hard-substrate communities in the southern hemisphere during that period. Diversity of encrusters and borers was compared among three bivalve species representing four successive intervals spanning ~10 Ma in the history of the Austral Basin. Crassostrea? hatcheri (Ortmann) built framework reefs in shallow shelf environments, and its valves form large biogenic and sedimentologic concentrations exposed in many areas of southern Patagonia. Data on 87 Sr/ 86 Sr rates in specimens from the San Julián Formation yielded a late Oligocene age (late Chattian) and an early Miocene age (early Burdigalian) for those from the Estancia 25 de Mayo Formation. Specimens of Reticulochlamys proximus (Ihering) presented mostly as biogenic concentrations also from shallowshelf environments in the Monte León Formation rendered an early Miocene age (late Burdigalian). The other oyster, Crassostrea orbignyi (Ihering), built reefs in more marginal estuarine environments, and their monospecific concentrations are intercalated in the lowermost beds of the early Miocene Santa Cruz Formation. Richness analyses of the sclerobiont communities on C.? hatcheri, C. orbignyi and R. proximus, revealed the presence of a) endobionts: fungi, algae? (Clionolithes isp., Dendrina isp.), sponges (Entobia isp.), polychaetes (Maeandropolydora isp., Caulostrepsis isp., Trypanites isp.), phoronids (Talpina isp.), bivalves (Gastrochaenolites isp.), gastropods (Oichnus isp.), bryozoans (Pennatichnus isp., Pinaceocladichnus isp.), brachiopods (Podichnus isp.), cirripedians (Rogerella isp.); b) epibionts: coralline algae, polychaetes (Serpulidae indet.), bivalves (Ostreidae, Anomiidae), bryozoans (Leptichnus isp., Cheilostomata indet., Cyclostomata indet.), cirripedians (Balanomorpha indet.); and c) vagile organisms: gastropods (Radulichnus isp.). Differences appear when diversity among the four samples of bivalve-hosted sclerobiont communities is compared. Richness is higher in Oligocene C.? hatcheri and in R. proximus (nine endobionts, seven epibionts and one vagile), and lower in Miocene C.? hatcheri (nine endobionts, three epibionts and one vagile). Instead, C. orbignyi contains only six sclerobionts. Dominance index is very low for the four samples and the Simpson index is high, indicating a high evenness with non-dominant taxa. Chi-squared test was used to test the likelihood of samples with taxon abundance data being from the same community. Results revealed that there are significant differences according to relative abundance among the four studied samples (p<0.001). These differences could be attributed to variations in the nature of the host organism (e.g., lifespan, shell thickness, size and ornamentation), and to differences in environmental conditions (including water depth, salinity and temperature) rather than to changes in sclerobiont diversity through time. In this sense, the sclerobiont community structure appears unaffected by the environmental disturbances occurring during the Paleogene/Neogene transition (e.g., Mi1 event). The relative abundance of borers in oysters is higher than that of encrusters; among them the most abundant are sponges and polychaetes, in agreement with other Cenozoic hard substrate communities studied elsewhere. However, this is not the case for pectinids, in which encrusters and borers occur in similar proportions. Clearly, more work is needed to better understand these diversity patterns. Future research on marine hard-substrate communities in the Cenozoic of Patagonia should include not only detailed bed by bed well-dated sampling, but also the examination of different host species in the same bed, and equivalent hard substrate in different environments. 18

19 Abstracts and Intra-symposium Fieldtrip Ichnology: sedimentologic and stratigraphic applications to the study of the Lower Cretaceous of the Neuquén Basin Pazos, P.J. Instituto de Estudios Andinos don Pablo Groeber (IDEAN), CONICET-UBA. Dpto. de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Ciudad Autónoma de Buenos Aires, Argentina, [email protected] The Neuquén Basin is one of the most studied basins in Argentina because it is one of the most important sources of conventional hydrocarbons in the country and a promising basin for unconventional reservoirs exploration worldwide. Ichnology, as a discipline involving both geology and paleontology, is a powerful tool for refining paleoenvironmental interpretations, particularly in areas where body fossils, both macro- and microfossils, are sometimes scarce, not diagnostic or absent. In the Neuquén Basin, the Lower Cretaceous is mainly recorded in a depositional sequence (Mendoza Group), including several marine units (Vaca Muerta, Mulichinco and Agrio Formations), which is unconformably covered by marginal marine and continental deposits of the Bajada del Agrio Group. The ichnological knowledge of each unit increases stratigraphically upward and is crucial to understand paleoenvironmental uncertainties, especially in the Agrio Formation. Until one decade ago, their marine members were ichnologically characterized as an example of the Cruziana ichnofacies, while the continental wedge was sterile. The detailed ichnological study of the unit, in particular the upper member, answered some questions regarding the nature and magnitude of the hiatus between the Mendoza and Bajada del Agrio Groups, and also explained the absence of classical biostratigraphic markers such as nannoplankton and ammonoids. Fortunately, such deposits are quite rich in ichnofossils, some of them documenting tracemakers unknown for the entire basin or, even more, for the Early Cretaceous worldwide. The upper sedimentary cycle that commences with a forced regression (Avilé Member) provided an ichnological record dominated by meniscated burrows such as Scoyenia, but also other structures such as Cochlichnus and poorly preserved tetrapod tracks that are included in fluvial and playa lake deposits. A geologically fast transgression linked with tectonic events in the proto-andean margin inundated the basin, allowing deposition of widespread black shales all over the basin. The succession is organized in stacked depositional sequences that contain the classical ichnofauna of the unit: Arenicolites, Chondrites, Diplocraterion, Ophiomorpha, Planolites, Palaeophycus, Skolithos, Teichichnus, Thalassinoides, and peculiar forms such as Bolonia and Nereites-like trace fossils. Asteriacites, a common ichnogenus in the underlying Mulichinco Formation is, on the contrary very scarce in the Agrio Formation. The uppermost sequence is the most interesting one because it shows evidence of strong tidal features including thinning-upward tidal cycles, starting with subtidal carbonate deposits conforming bars and channels followed by heterolithic to muddy deposits, locally reaching supratidal settings. The ichnofauna recorded in the carbonatic deposits is located in the east of the engulfment. In two localities, theropod tracks (Therangospodus) were found; the producers walked along the coast, leaving their tracks in deposits previously interpreted as basinal facies. In places, transgressive intervals are clastic and transgressive surfaces contain intense bioturbation including Rhizocorallium/Ilmenichnus examples. The intertidal deposits are the most attractive ones from an ichnological perspective. There are rare and multiethological ichnogenera such as Hillichnus, attributed to infaunal tellinid bivalves, and Kouphichnium, produced by xiphosurids which, in this case, probably arrived to these shallow water areas during mating season. Other ichnofossils under study record the feeding activity mainly of bivalves. Microbial mats are very abundant and had a key role in the preservation of small undermat miners, such as Cochlichnus and Treptichnus. After some years of research, marginal marine environments dominated by tidal action, salinity fluctuations where microbially controlled surfaces flourished, permit to explain the absence of normal marine biostratigraphic markers as ammonoids and nannoplankton. Then, their absence is not longer attributable to intense erosion between the Mendoza and the Bajada del Agrio groups, as traditionally was suggested. 19

20 SLIC2013 Second Latin American Symposium on Ichnology Ichnostatistics applied to sedimentary models and oil basin analysis Poiré, D.G. Centro de Investigaciones Geológicas (UNLP-Conicet), La Plata, Argentina, The use of statistical tools has been widely applied in science in general and also particulary in natural sciences. Geology and paleontology have not been the exception. Furthermore, in the beginning of ichnology, statistics have been used primarily in ichnotaxonomy, especially for the identification of ichnoespecies through morphometric measures, which it is not accepted today in the ichnotaxobase concept. In the last decades, new numerical concepts have been introduced, such as the maximum diameter of traces or the bioturbation index that have led to interpret environmental aspects, such as oxygenation and salinity. Recent sedimentological investigations, carried out in the Paleozoic of the Bolivian Subandean region, have provided new advances and applications (what is here called Ichnostatistics ) to unlock the paleoenvironmental distribution of trace fossils, ichnofacies and ichnolitological associations. On the other hand, this analysis tries to link their results with geoelectric tools largely used in the oil industry. Surprisingly, in this case the geoelectric logs reflect the trace fossil content rather than the recorded lithology. The aim of this talk is to show the results and the methodology of one of the most successful studies about the Huamampampa Formation, which includes measurement every 5 cm of Numerical Facies (NF), Bioturbation Index (BI), Ichnodiversity Index (IdI), Ichnogenus Size Ordering (ISO), and the geostatistic analysis of their obtained curves. The Huamampampa Formation had been classically interpreted as the product of shallow open-marine sedimentation in a Devonian shelf. However, this ichnological and sedimentological studies conducted in six cores and three outcrops have allowed the recognition of the occurrence of a brackish water interval.trace fossils identified in cores and outcrops include Arenicolites, Asterosoma, Bergaueria, Chondrites, Cylindrichnus, Diplocraterion, Helminthopsis, Macaronichnus, Neonereites, Palaeophycus, Phycodes, Planolites, Rhizocorallium, Rosselia, Skolithos, Teichichnus, and Zoophycos.These ichnogenera are grouped in the Cruziana, Skolithos and an impoverished ichnofacies. Then, ichnofacies and ichnolithological associations have been used to recognize different subenvironments in a tide-dominated delta (or estuarine)- shallow marine environment. The ichnolithological associations identified are i) Sandy facies with Cruziana Ichnofacies (S-Cr), high bioturbation and ichnodiversity (assigned to shallow marine, upper shoreface); ii) Sandy facies with an Impoverished ichnofacies (S-Imp), low bioturbation and ichnodiversity, general size reductions of ichnogenera (tide-dominated delta or estuarine, longitudinal bars, brackish water); iii) Sandy facies with the Impoverished-Skolithos Ichnofacies (S-Imp-Sk), low bioturbation and ichnodiversity, isolated Skolithos (top of longitudinal bars, high-energy pulses); iv) Sandy facies with belts of Arenicolites (S-bAr), horizontal levels of just Arenicolites up to 5 cm thick (high energy pulses crossing different facies, in the delta front or in the shoreface); v) Sand-rich heterolithic facies with the Cruziana Ichnofacies (Hts-Cr), moderate bioturbation and ichnodiversity (shallow marine, upper to middle shoreface); vi) Sand-rich heterolithic facies with Cylindrichnus and Rosselia (Hts-Cyl-Ros), moderate bioturbation and low ichnodiversity (shallow marine, upper shoreface); vii) Heterolithic facies with the Cruziana Ichnofacies (Ht-Cr), high bioturbation and ichnodiversity (shallow marine, transition zone between lower shoreface and offshore, open shelf); viii) Heterolithic facies with an Impoverished ichnofacies (Ht-Imp), low bioturbation and ichnodiversity, reduced size of trace fossils (tide-dominated delta or estuarine, delta front, brackish water); and ix) Sandy facies with no bioturbation (S-Not Biot), interpreted as fluvial channels. 20

21 Abstracts and Intra-symposium Fieldtrip Abstracts 21

22 SLIC2013 Second Latin American Symposium on Ichnology 22

23 Abstracts and Intra-symposium Fieldtrip Environmental constraints of a Middle Ordovician trace fossil association from the Lina Formation (Puna of Jujuy province, NW Argentina) Aceñolaza, G. 1, Bayetgoll, A. 2, Nieva, S. 1 and Aráoz, L. 1 1 INSUGEO (Instituto Superior de Correlación Geológica), CONICET Universidad Nacional de Tucumán, Argentina, [email protected] 2 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Iran The Ordovician strata of the Puna region in NW Argentina is represented by a succession of siliciclastic marine facies associated to syn-sedimentary volcanism. Three phases of basin evolution during the the Tremadocian-Darriwilian have been recognized, Platform, Volcanic and Turbidite complex. The Lina Formation is part of the Puna Turbidite Complex, and is represented by a thick sequence of slightly metamorphosed and highly deformed shales and sandstones reaching up to ca. 900 m of thickness. The unit is divided in three members, and was interpreted as deposited in depositional lobes associated to advancing or shifting channels. A Darriwilian age has been proposed for the unit on the basis of poorly preserved, graptolites that were determined as Eoglyptograptus cf. E. dentatus, Glyptograptus (?Oelandograptus sp.), Archiclimacograptus sp., Oelandograptus? sp. and Glossograptus hincksii fimbriatus. The unit displays an impoverished trace fossil association characterized by shallow tier small-sized traces including Helminthoidichnites tenuis, Lockeia? isp. and few irregularly distributed low-reliefs knobs. Trace fossils are preserved on the upper and lower surfaces of up to 10 cm thick sandstone beds present in thick packages of parallel-laminated finegrained sandstones and shales. Microbial mat related structures are rare, and mostly represented by wrinkle marks, while pyrite mineralization is common within the fine-grained sandstones and shales. The paucity of paleontological evidence has precluded a detailed interpretation of the biota and its relation to this complex depositional scenario. A better understanding of the relationships between the sedimentary and the fossil record will help to decipher environments and the geodynamic evolution of the region during the Ordovician. 23

24 SLIC2013 Second Latin American Symposium on Ichnology Bioeroded bone fragments from the late Miocene of Hungary Arpad, D. and Apró, A Karoly Eszterhazy College, Department of Geography, Eger, Hungary, [email protected] 2472 vertebrate bone remains, collected at the sandpit of Danitz-puszta, have been examined. The fossils could be divided into two main groups regarding their age and environment. The first one is the bones of marine animals older than Late Miocene. The second group contains the bones of Pliocene and Pleistocene age terrestrial animals. The number of the marine vertebrate remains is 411, while the number of the terrestrial vertebrate bones is The preservation of the bones belonging into the latter cluster is very poor; mainly fragmentary, and therefore, only 64 terrestrial bone remains have been determined. The poorly preserved terrestrial bone fragments have been placed into three groups: undeterminate jaw fragments; teeth remains; and fragments of limbs. Bioerosion structures have been observed on the poorly preserved teeth and limb fragments in all cases. The observed traces of bioerosion have been clustered into six groups according to their shape, size, and state of preservation: 1 Cubiculum cf. ornatus: Ovoid, shallow hollows, 7-11 mm long, 3-5 mm wide, and 2-3 mm deep. They occur in both the compact and spongy parts of the bones. There are no ornamentations on the wall of the small chambers. 2 Breeding trace of necrophagous insects: Elongated borings ending in a rounded chamber, 11 mm long, 2 mm wide. Chamber is 4 mm wide. 3 Feeding trace of necrophagous insects: Elongated trails or rounded pits. Trails are 10 mm long and mm wide. They occur in both the compact and spongy parts of the bone fragments. The pits are situated alone or forming groups. Pits are 2-4 mm wide and mm deep. 4 Wearing marks on the surface of teeth: Marks are 5-11 mm long and mm wide. Most of the marks meet in acute angle. 5 Chewing marks 1: Irregular V-shaped trace fossils at the end of elongated bones. 6 Chewing marks 2: Parallel scratch marks on the surface of elongated bone fragments. 24

25 Abstracts and Intra-symposium Fieldtrip Evidence of arthropod-plant interactions on early Oligocene leaves Arpad, D. 1, Torba, K. 1 and Fodor, R. 2 1 Karoly Eszterhazy College, Department of Geography, Eger, Hungary, [email protected] 2 Mátra Muzeum, Gyöngyös, Hungary Outcrops of the early Oligocene Tard Clay Formation located NE of Eger, Northern Hungary, contain abundant plant remains. The objectives of this study are to document the ichnologic evidence of arthropod-plant interactions and to discuss the paleoecological connection between the plants and the tracemakers. The examined fossil leaves are housed in the paleobotanical collection of the Matra Museum, at Gyöngyös, North-Hungary. Of the 3395 leaf remains examined, 202 show evidence of interactions. Nine types of interactions have been recognized: 1) hole feeding; 2) margin feeding; 3) skeletonization; 4) surface feeding; 5) piercing; 6) oviposition; 7) mining; 8) galling; and 9) undeterminate. Hole feeding was the dominant. The dominance of subtropical forest is inferred from the plant remains. The most frequent plant taxa displaying evidence of arthropod-plant interactions are Castanopsis furcinervis, Dryophyllum sp. and Zizyphus zizyphoides. The feeding and breeding traces suggest the activity of Lepidoptera, Hemiptera, Hymenoptera, Diptera and Coleoptera. 25

26 SLIC2013 Second Latin American Symposium on Ichnology Trace fossils and environments of the Shirgesht Formation (Ordovician of Kamard, central Iran) Bayetgoll, A. 1, Aceñolaza, G. 2, Moussavi-Harami, R. 1 and Mahboubi, A 1. 1 Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Iran. [email protected] 2 INSUGEO (Instituto Superior de Correlación Geológica), CONICET Universidad Nacional de Tucumán, Argentina The early Paleozoic successions of northern Gondwana have been historically referred as a classical area for the study of shallow marine trace fossil assemblages, with many papers providing information on paleoenvironment and stratigraphy. This diverse ichnological dataset mostly comes from northern Africa, with a notable lack of information from the Middle East. The Early to Middle Ordovician siliciclastic successions of the Shirgesht Formation cropping out in the Kalmard area of central Iran are highly significant as being the best known Gondwanan successions to yield arthropod traces. Herein we use the ichnology of the unit to reveal insights into the shallow marine paleoenvironments, and to compare with other known arthropod traces-bearing localities across Gondwana. The Shirgesht Formation is represented by a thick sequence dominated by sandstones and shales displaying a remarkable ichnofauna. Six trace fossil assemblages were identified as follows: (1) a distal Cruziana Ichnofacies, (2) an archetypical Cruziana Ichnofacies, (3) the mixed Skolithos- Cruziana Ichnofacies, (4) the distal Skolithos Ichnofacies, (5) the archetypal Skolithos Ichnofacies, and (6) impoverished expression of the Skolithos Ichnofacies. These assemblages inhabited a spectrum of offshore, shoreface to tidal flat environments. This ichnofauna provides a well-preserved example of a typical Ordovician epeiric sea assemblage, and records the diverse ethologies of trace makers in shallow marine environments. This study suggests that the widespread occurrence of heterolithic deposits from upper offshore to lower shoreface settings contain ichnofacies dominated by shallow-tier structures, such as trilobite trails and trackways, which seem almost diagnostic of the early Paleozoic. Many early Paleozoic shallow marine settings were typified by laterally extensive sand-rich nearshore environments and opportunistic colonization of substrates by large pipe rockproducing communities of burrowing suspension feeders. 26

27 Abstracts and Intra-symposium Fieldtrip Digging into paleosol - trace fossil relationships Bellosi, E.S. 1, Krause, J.M. 2 and Bedatou, E. 3 1 CONICET, Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina, [email protected] 2 CONICET, Museo Paleontologico E. Feruglio, Trelew, Argentina 3 CONICET, INCITAP, Santa Rosa, Argentina Integrated analysis of paleosols and trace fossils, helped with neoichnological studies, are making good progress in the interpretation of environmental and ecological conditions of ancient terrestrial ecosystems. Paleosol development reflects ecological succession, whereas trace fossil assemblages can record ecological preferences and organismal behaviors of soil biota. In order to recognize recurrent patterns, paleosols and invertebrate trace fossils were analyzed in a hundred, mostly Cenozoic, cases. Paleosols were arranged taxonomically into ten soil orders (U.S. Depart. of Agriculture). Entisols and Gelisols were excluded because uncertain or insufficient information. Raw data include 55 invertebrate traces, mostly (36) insect ichnogenera (termites, beetles, solitary/social bees, wasps, ants, cicadas, sphinx moths), earth worms (4), crustaceans (6) and undetermined (9) traces. Rhizoliths (rhizohaloes, rhizocretions, rhizotubules, rhizospheres) are grouped into small/fine (< 5 mm in diameter) and large or tree stumps, because they are not taxonomically studied. Preliminary results show particular relationships between most soil orders, ichnofossils and trace makers. Oxysols and Spodosols have very scarce ichnological information because they are uncommon paleosols in the stratigraphic record. The remaining soil orders contain on average13different trace fossils (range 9-18). Four of them are exclusive for each paleosol (range 2-7). On average, each trace fossil occurs in two soil orders, but not more than in five. More than half (29) of traces are present in only one paleosol type. Ultisols (7) and Inceptisols (6) show the greatest number of exclusive traces. Ichnodiversity is maximum in Andisols, clayey paleosols and Inceptisols; and minimum in oxic, carbonaceous and calcic paleosols. Ichnologically, the more similar paleosols are Andisols and Mollisols, with nine traces in common. Beetle and earth worm traces are the most ubiquitous (in all soil orders), followed by bee, termite and crustacean, and finally ant, cicada and sphinx moth traces. Alfisols exhibit the highest diversity in trace makers inhabiting soils from subhumid-semiarid, open forests or wooded grasslands. They include beetle (Coprinisphaera, Pallichnus, Rebuffoichnus, fecal pellets), bee (Celliforma, Celicalichnus), crustacean (Loloichnus), termite (Termitichnus, clay micro aggregates), earth worm (Lazaichnus, fecal pellets: fp), sphinx moth (Teisseirei) and ants traces. Ultisols present abundant traces developed in soils from temperate-warm, humid-subhumid forests or wooded grasslands: bees (Palmiraichnus, Uruguay, Ellipsoideichnus, Corimbatichnus), termites (Krausichnus, clay micro aggregates), beetles (Rebuffoichnus, Coprinisphaera), sphinx moths (Teisseirei), cicadas (Monesichnus), earth worms (Lazaichnus) and crustaceans (Guerraichnus). Mollisols originate in semiarid-subhumid grasslands, and also include traces from numerous producers: beetles (Coprinisphaera, Pallichnus, Quirogaichnus, fp), earth worms (Edaphichnium, Castrichnus, fp), small roots, and subordinately from termites (Syntermesichnus, unnamed nests), bees (Celliforma, Palmiraichnus), ants (Attaichnus) and cicadas. Aridisols develop in dry climates with desert scrub or sparse vegetation. They show a low-diversity ichnological assemblage with bee (Celliforma, Rebuffoichnus, Roselichnus), beetle (Pallichnus, Fictovichnus, Rebuffoichnus) and termite (Termitichnus, unnamed nests) traces. Vertisols evidence marked seasonal variations in humidity. They bear earth worm (Edaphichnium), beetle (Scaphichnium), crustacean (Camborygma) and cicada (Naktodemasis) traces, but abundant undetermined ones. Peaty soils such as Histosols, support bog, swamp and marsh in cool, humid-subhumid conditions. They contain earth worm (fp) and beetle (Eatonichnus) traces, along with Macanopsis, Planolites, Steinichnus and Fuersichnus. Earlier successional communities are represented by Andisols and Inceptisols. Unlike previous views and lack of time, these weakly-developed paleosols show high ichnological diversity. Andisols, developed on volcanic ash, show traces of beetles (Coprinisphaera, Pallichnus, Eatonichnus, Chubutolithes, Rebuffoichnus, Scaphichnium), crustaceans (Loloichnus, Dagnichnus, Cellicalichnus, Taenidium, Beaconites) and earth worms (Edaphichnium, Castrichnus, Lazaichnus, fp), subordinately traces of cicadas (Feoichnus, burrows) and bees (Celliforma), and only one undetermined trace. Inceptisols include numerous termite (Socialites, Fleaglellius, Vondrichnus, other nests), beetle (Pallichnus, Fictovichnus, Scaphichnium), ant (Parowanichnus), crustacean (Katbergia) and earth worm (Edaphichnium, fp) traces. 27

28 SLIC2013 Second Latin American Symposium on Ichnology Boring and encrusting barnacles through the Cretaceous/Paleogene boundary in northern Patagonia (Argentina) Brezina, S.S. 1, Romero, M.V. 2, 3 and Casadío, S. 1, 3 1 Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro (UNRN), Gral. Roca, Argentina, [email protected] 2 Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Mar del Plata, Argentina 3 Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina Barnacles are found in all oceans and estuaries, distributed from the tropics to the poles and from the intertidal zone to the abyssal depths. The radiation of barnacles is reflected by the variety of substrates that they are able to attach or bore, including biogenic and abiogenic substrates. The group is considered successful in terms of abundance and diversity. Barnacles have adaptive strategies to occupy and persist in widespread, diverse, and physiologically challenging environments. Little is known about this group as a fossil constituent of encrusting and boring communities associated to hard substrates from middle latitudes in Southern Hemisphere. The changes in these communities during episodes of extinction like those that occurred during the Cretaceous/Paleogene boundary are almost unknown. This work reports the encrusting and boring barnacles associated to oysters from the K-Pg boundary and their changes in their relative abundances. The barnacles and their traces studied here come from 1,174 oysters specimens belonged to Pycnodonte (Ph.) vesicularis, Turkostrea damboreneae and Amphidonte mendozana (late Maastrichtian), Gryphaeostrea callophylla, Pycnodonte (Ph.) burckhardti and Turkostrea argentina (early Danian) and Ostrea wilckensi, Pycnodonte (Ph.) sarmientoi and Cubitostrea ameghinoi (late Danian). The barnacles identified on the oyster shells belong to Acrothoracica (boring barnacles) and Thoracica (encrusting barnacles). Boring barnacles are represented by traces assigned to Rogerella De Saint-Seine, This trace does not show significant differences in the relative abundance at the K-Pg boundary, however, during the late Danian it was more common. The encrusting barnacles were assigned to Verruca Schumacher, Verruca spp. and their traces Centrichnus ispp. are absent during the late Maastrichtian, show very low abundance in the early Danian and high abundance in the late Danian. These results suggest that boring barnacles were not affected by the environmental disturbances at the K/Pg boundary. However during the late Danian it was recorded a significant increase of encrusting barnacles. This change after the earliest Danian correlates with an increase in the number of species of corals, mollusks, echinoids and crabs derived from low latitudes, reflecting higher seawater temperatures spreading south. 28

29 Abstracts and Intra-symposium Fieldtrip Ichnologic insights into the early colonization of the deep sea Buatois, L.A. and Mángano, M.G. Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada. Trace- and body-fossil evidence indicates that the colonization of the deep sea started in Ediacaran times. In fact, the oldest trace and body fossils are known from deep-marine deposits (Avalon assemblage), although their phylogenetic affinities are uncertain, being most likely unrelated to bilaterians. Younger Ediacaran (e.g. Mackenzie Mountains) deep-marine ichnofaunas consist of very simple trails and burrows, essentially representing four main architectural designs [simple horizontal trails, passively filled horizontal burrows, actively filled (massive) horizontal burrows, plug-shaped burrows]. Global and alpha ichnodiversity, as well as ichnodisparity, were extremely low. Nonspecialized grazing trails (e.g. Helminthopsis, Helminthoidichnites) reveal the exploitation of microbial mats, a strategy that was also dominant in Ediacaran shallow-marine environments. However, whereas microbial mats underwent a progressive environmental restriction in shallow, fully marine settings after the Cambrian agronomic revolution, matground exploitation persisted during most if not all the Cambrian in the deep sea. Cambrian deep-marine ichnofaunas are of Ediacaran aspect, and the deep sea can be regarded as a relict ecosystem. Notably, the Cambrian radiation is expressed in the deep sea by the addition of a number of architectural designs, most notably surface-coverage branching burrows (e.g. Oldhamia), horizontal to oblique branching burrows (e.g. Saerichnites), trackways and scratch marks (e.g. Diplichnites) and smooth bilobate trails and burrows (e.g. Didymaulichnus), which reflect the appearance of novel body plans. As a result, Cambrian deep-marine ichnofaunas display a remarkable increase in ichnodisparity, as well as in global and alpha ichnodiversity. Deep-marine environments undertook significant changes by the end of the Cambrian, reflecting the seaward expansion of the agronomic revolution and the demise of matground-dominated ecosystems. The main architectural designs of deep-marine trace fossils (e.g. regular networks, delicate spiral burrows, guided meandering graphoglyptids) were established in the deep sea by the Early Ordovician, recording the first appearance of the Nereites Ichnofacies. Lower to Middle Ordovician deep-marine ichnofaunas are moderately diverse, and fodinichnia commonly dominates rather than graphoglyptids. A significant ichnodiversity and ichnodisparity increase occurred in the Late Ordovician-Early Silurian, with ichnofaunas recording higher proportions of graphoglyptids and evidencing the establishment of a deep-marine ecosystem of modern aspect. In short, the early colonization of the deep sea reveals three main phases: Cambrian exploitation of microbial mats, Lower Ordovician dominance of deposit- and detritus feeding and Upper Ordovician to Silurian establishment of trapping and bacterial farming. In the common absence of body fossils, trace fossils represent a unique source of information to understand the early evolution of deep-sea ecosystems. 29

30 SLIC2013 Second Latin American Symposium on Ichnology Caracterización icnológica de sistemas de barras deltaicas de la Formación Lajas en la Sierra de la Vaca Muerta (Jurásico Medio), Cuenca Neuquina, Argentina. Canale, N. 1, Ponce, J.J. 2, Carmona, N.B. 2 y Drittanti, D.I. 3 1 Instituto Geológico del Sur INGEOSUR - CONICET, Universidad Nacional del Sur - Departamento de Geología, Bahía Blanca, Argentina, [email protected] 2 CONICET, Universidad Nacional de Río Negro - Instituto de Investigación en Paleobiología y Geología, General Roca, Río Negro, Argentina 3 Universidad Nacional del Sur - Departamento de Geología, Bahía Blanca, Argentina El análisis sedimentológico e icnológico del tramo superior de la Formación Lajas (Jurásico Medio) en la zona norte de la Sierra de la Vaca Muerta, permitió reconocer una sucesión de 150 m de espesor integrada por areniscas y conglomerados acumulados en sistemas de barras y lóbulos deltaicos. El análisis detallado de los sistemas de barra permitió reconocer dos tipos de arreglos con asociaciones icnológicas diferentes. El primero corresponde a un sistema de barras integrado por areniscas y conglomerados que muestran estratificación entrecruzada tangencial de gran escala y que se encuentran parcial o totalmente retrabajadas por acción de oleaje (normal y de tormenta). El contenido icnológico de estas barras muestra la mayor diversidad y abundancia de trazas fósiles con ejemplares de Ophiomorpha, Skolithos, Macaronichnus, Dactyloidites y Curvolithus. El otro arreglo corresponde a sistemas de barras integradas por areniscas gruesas a finas masivas o con estratificación entrecruzada tangencial de gran escala y óndulas de corriente que migran en dirección opuesta a la de la migración de la cara frontal de la barra. Hacia el techo de estas barras es frecuente observar un importante retrabajo por acción de oleaje (normal y de tormenta). El contenido icnológico de estas barras muestra una menor diversidad, representada por trazas de equilibrio/escape, Ophiomorpha y Skolithos. De manera preliminar se interpreta que las diferencias sedimentológicas e icnológicas que muestran estos depósitos, reflejan un control en la magnitud que tuvieron las descargas fluviales que dan origen a estas barras deltaicas. De este modo, las barras clásticas que muestran un importante retrabajo por acción de oleaje, se habrían generado durante ciclos en los cuales las descargas fluviales fueron de baja magnitud. Este tipo de procesos favoreció la generación de ventanas de colonización recurrentes y temporalmente estables que permitieron el desarrollo de estructuras biogénicas asignables a la Icnofacies de Skolithos con elementos de la Icnofacies de Cruziana. Internamente este tipo de barras se caracteriza por presentar Ophiomorpha y Dactyloidites en las caras de avalancha, y una suite dominada por Macaronichnus, Curvolithus y Skolithos en el topset de las barras. Contrariamente, las barras deltaicas integradas por arenas gruesas a finas que muestran estratificación entrecruzada tangencial y retrabajo por acción de oleaje al techo, se habrían generado durante ciclos en los que las descargas fluviales presentaron mayor magnitud. En este caso las barras muestran el desarrollo de la Icnofacies de Skolithos, con desarrollo de trazas de equilibrio/escape y Ophiomorpha en las caras de avalancha, y una fábrica dominada por Skolithos en las zonas más energéticas (topset) de las barras. El análisis a futuro del patrón de apilamiento que presentan estos sistemas de barras, permitirá estimar las variaciones en la magnitud de las descargas fluviales que experimentó este sistema deltaico. Estudio financiado por PIP 417-CONICET. 30

31 Abstracts and Intra-symposium Fieldtrip Paleoenvironmental implications of resting, locomotion and equilibrium/ escape structures of freshwater bivalves, Río Negro Formation (late Miocene-early Pliocene) Carmona, N.B. 1, Ponce, J.J. 1, Wetzel, A. 2, Bournod, C. 3 and Cuadrado, D. 3, 4 1 CONICET, Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, General Roca. Rio Negro, Argentina. [email protected] 2 Geologisch Paläontologisches Institut, Universität Basel, Basel, Switzerland 3 CONICET, Instituto Argentino de Oceanografía, Bahía Blanca, Argentina 4 Departamento de Geología, Universidad Nacional del Sur, Bahía Blanca, Argentina Unionid are freshwater bivalves that live buried in muddy or sandy sediments in fluvial and marginal-lacustrine environments. These bivalves are suspension-filter feeders that form dense communities. Trace fossils produced by unionid bivalves are extremely common in wet-interdune deposits of the continental members of the Río Negro Formation (Late Miocene-Early Pliocene), forming almost monospecific assemblages. Based on ichnologic and sedimentologic analyses of these deposits, the paleoenvironmental evolution of these wet-interdune settings can be inferred. When the water level was high and relatively stable, bivalves colonized the muddy bottom, producing a great abundance of resting structures (cubichnia), most of which were oriented to the dominant currents. Some of these specimens are connected to lateral chevronate structures (repichnia), which are interpreted as short displacements of the bivalves during changes in current direction. In some of the wet-interdunes, water level dropped to the point of desiccation. In those cases, the resting and locomotion structures are found in association to desiccation cracks and they were covered subsequently by the migration of adjacent dunes. A different scenario is found if the dune migration occurred while the wet-interdunes were active. In these cases, the bivalves produced equilibrium or escape structures depending on the thickness of eolian sand deposited to keep pace with the continuous input of sand. At the end of some of these structures, the producer s body fossils are preserved. These examples show that the information obtained from the ichnologic data has important implications for the understanding of the paleoenvironmental evolution of these Neogene eolian systems. Financial support for this study was provided by the grants PI-UNRN A-158; PICTO-UNRN ; PICT and SNF grant

32 SLIC2013 Second Latin American Symposium on Ichnology Microbial mats and the preservation of invertebrate trace fossils from the Sousa Basin (Early Cretaceous), Brazil Carvalho, I.S. and Borghi, L. Universidade Federal do Rio de Janeiro, Instituto de Geociências, Departamento de Geologia, Rio de Janeiro, Brasil, The Sousa Basin is one of the interior basins of northeast Brazil, whose origin and development were controlled by wrench tectonics related to the Gondwana break-up. The main Lower Cretaceous siliciclastic rocks include breccias, conglomerates, sandstones, and more typically, siltstones, mudstones and shales, where abundant invertebrate and vertebrate ichnofaunas are characteristic. These rocks show a strong reddish color, related to oxidizing terrestrial environments. The invertebrate trace fossils from the Sousa Basin are found in two distinct alluvial contexts. The larger ones occur in the sandstones interpreted as distal alluvial fan deposits (Antenor Navarro Formation); they are 1.5 m long, but are rare and restricted to a few sites. The other context of occurrence of the invertebrate ichnofauna are the siltstones and mudstones (Sousa Formation), interpreted as floodplain deposits. In both cases, the trace fossils occur as full- and semirelief. These trace-fossils are mainly related to organisms that fed on organic detritus found in the substrate (Fodinichnia), such as those produced by recent arthropods and annelids. The depositional paleoenvironment was probably very rich in nutrients, wet or humid, allowing the maintenance of an abundant and diverse benthic community. The absence of invertebrate trace fossils in some stratigraphic levels is related to occasional bottom/ surface reworking by currents, disturbing the depositional surface, and preventing the record of benthic biogenic activity. Microbially induced sedimentary structures associated to these invertebrate trace fossils show not only the role of microbial mats in the stabilization of the microenvironment of the trace-fossil producers, but also in the taphonomic processes. Microbial mats or biofilms acted preventing desiccation of the surface sediments; fixing and recycling nutrients, protecting mainly pupae, larvae and adult insects; and even serving as food for grazers. These ancient mats/biofilms also acted enhancing the trace fossil preservation, by biostabilizing the surface sediments against erosion/deflation; trapping and binding new sediments that bury the trace fossils; and promoting early cementation by carbonates or sulphates. This study was supported by CNPq, FAPERJ and PFRH-Petrobras/Biossedimentologia. 32

33 Abstracts and Intra-symposium Fieldtrip Primeras aproximaciones en la caracterización icnológica de la Formación Alta Vista: implicancias paleoambientales. Cereceda, A., Poiré, D.G., Richiano, S. y Varela, A.N. Centro de Investigaciones Geológicas CONICET-UNLP. La Plata, Argentina, [email protected] La Formación Alta Vista es parte del relleno sedimentario del Cretácico superior la Cuenca Austral, localizada al sur de la Patagonia Argentina. La localidad tipo, donde se relevaron los datos del presente trabajo, se encuentra en las barrancas de Alta Vista ubicadas al sudoeste de la ciudad de El Calafate, en la provincia de Santa Cruz. La Formación Alta Vista sobreyace en paraconcordancia a las sedimentitas marinas de la Formación Cerro Toro (Cretácico inferior) y es cubierta en concordancia por los depósitos marino-continentales de la Formación La Anita (Campaniano-Maastrichiano). Esta unidad está conformada por estratos tabulares de areniscas grises finas a muy finas, laminadas y masivas interpretadas como depositadas en un ambiente marino. El presente trabajo plantea una primera aproximación en detalle de la icnología presente en la Formación Alta Vista, con el fin de aportar una herramienta a la caracterización de los procesos sedimentarios y el paleoambiente de depositación de dicha unidad. En la sección estudiada se reconocieron cuatro intervalos sobre la base de las características icnológicas, que de base a techo son, Intervalo 1 (2m): vaques finas a muy finas con laminación paralela y masivas, con abundantes trazas de tipo domichnias y fodichnias y moderada icnodiversidad en donde se reconocen Rhizocorallium, Thalassinoides, Bergaueria, Gordia y Ophiomorpha; Intervalo 2 (1 m): arenita muy fina masiva con abundante bioturbación pero con muy baja icnodiversidad, representada sólo por el icnogénero Rhizocoralium; Intervalo 3 (aprox. 30 m): intercalaciones de vaques laminadas y masivas con limolitas masivas y heterolíticas prácticamente con ausencia de trazas, salvo por un solo nivel que presenta alta bioturbación conformada únicamente por Planolites de pequeño y mediano tamaño en la facies heterolíticas; Intervalo 4 (7 m): vaques finas laminadas y masivas con moderda bioturbación representada únicamente por el icnogénero Rhizocorallium. De la interpretación sedimentológica e icnológica se desprende que estas facies fueron depositadas en un ambiente marino de moderada a baja energía con un aporte constante de sedimentos finos. En un principio, el ambiente reinante presentaba condiciones estables de buena oxigenación, salinidad normal y aporte de alimentos propicias para la instalación y desarrollo de fauna epi y endobentónica. Contrastantemente, la ausencia de bioturbación en la mayor parte del intervalo 3, junto con la presencia Planolites de pequeño tamaño, podría indicar que hubo un cambio en los factores ambientales que no permitió la proliferación de la fauna, como podría ser aumento en la tasa de sedimentación, variaciones en la oxigenación o en la salinidad. Hacia el tope, en el intervalo 4, reaparecen abundantes trazas de Rhizocorallium. Este cambio abrupto en la icnología, con respecto al intervalo anterior, podría estar reflejando una nueva variación en las condiciones ambientales, debido a que en esta última etapa las condiciones parecen haber vuelto a ser más estables, con alta oxigenación y salinidad normal, que permitió nuevamente la instalación de organismos. 33

34 SLIC2013 Second Latin American Symposium on Ichnology Icnocenosis de vertebrados e invertebrados en el Subgrupo Balbuena (Maastrichtiano-Daniano), Quebrada de Humahuaca, noroeste argentino Cónsole-Gonella, C.¹, de Valais, S.², Sánchez, M.C. 3, Marquillas, R.A. 4 y Herrera Oviedo, P.¹ ¹Instituto Superior de Correlación Geológica (INSUGEO) Universidad Nacional de Tucumán-CONICET, Tucumán, Argentina, [email protected] ²CONICET Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, General Roca, Río Negro, Argentina ³Instituto del Cenozoico INCE Universidad Nacional de Salta, Complejo Universitario Castañares, Salta, Argentina. 4 CONICET Universidad Nacional de Salta, Complejo Universitario Castañares, Salta, Argentina. El Subgrupo Balbuena (Maastrichtiano-Daniano) corresponde al estadio de postrift temprano de la cuenca del Grupo Salta (Neocomiano-Eoceno); en el tramo austral de la Quebrada de Humahuaca (provincia de Jujuy), los afloramientos de esta unidad son de naturaleza clástica (Formación Lecho) y carbonática (Formación Yacoraite), y en ellos se reconocieron trazas fósiles de vertebrados e invertebrados. En base al análisis de las facies sedimentarias es posible dividir a la sección relevada (50 m de espesor) en tres secciones: una basal granodecreciente, de 20 m de espesor, que varía de conglomerado oligomíctico mal seleccionado, con clastos angulosos de naturaleza aluvial, a arenisca gruesa fluvial tipo braided. La sección media, de 5 m de espesor, se compone de areniscas depositadas a partir de mantos de crecida (sheet flood). La sección superior, con un espesor de 25 m, es esencialmente carbonática (grainstone, wackestones y mudstones) y su acumulación habría ocurrido en un ambiente de lagoon protegido asociado a una planicie supramareal. Esta porción es portadora de abundantes y variadas trazas de vertebrados e invertebrados, correspondientes a: 1) improntas de mano semicirculares (diámetro: 33 cm) y pie de contorno triangular (largo: 56 cm, ancho: 44 cm), relacionadas con saurópodos titanosaurios de gran tamaño; 2) huellas tridáctilas (largo: 40 cm, ancho: 37 cm), asignadas a terópodos; 3) huellas didáctilas, de origen desconocido (largo: 15 cm, ancho: 7 cm), formada por dos trazas elongadas semiparalelas ocasionalmente unidas proximalmente; 4) improntas de mano tetradáctila o pentadáctila, sobreimpresa por el pie, sin detalles morfológicos, posiblemente conferibles a estegosaurios. En los niveles superiores de esta sección carbonática se reconocieron dos tipos de huellas avianas, de improntas digitales delgadas y formando ángulos amplios. El primero corresponde a una huella parcial, similar a Yacoraitichnus, con el dígito central recto y un lateral de contorno basalmente recurvado convexo, formando un ángulo de 43º. El segundo tipo está representado por improntas tridáctilas y tetradáctilas, casi tan anchas como largas (largo incluyendo hálux: 11 cm, ancho: 9 cm), con impresiones digitales delgadas sin almohadillas y con garras aguzadas. Los dígitos I y III forman un ángulo de 170º. Las trazas de invertebrados asociadas son: Lockeia siliquaria, Taenidium barretti, Planolites isp., Thalassinoides isp. y Skolithos linearis y Arenicolites isp., en icnofábrica de tipo pipe rock. Por otro lado, en esta sección es típico el desarrollo de estromatolitos dómicos lateralmente adosados con una altura promedio de 70 cm. Desde el punto de vista icnofacial la icnocenosis detallada puede ser conferida a la Icnofacies de Scoyenia en sentido amplio, ya que sobre la base del estado de conocimiento del tema, puede ser apropiada una subdivisión de esta icnofacies. En cuanto a su correlación regional, el registro icnológico descripto es comparable al de las formaciones Vilquechico (Maastrichtiano Tardío) de Perú y El Molino (Maastrichtiano-Daniano) de Bolivia. 34

35 Abstracts and Intra-symposium Fieldtrip Burrow architecture and burrowing dynamics of Ctenomys sp. in southern Brazil foredunes Dentzien Dias, P.C. 1 and Quezado de Figueiredo, A.E. 2 1 Núcleo de Oceanografia Geológica, Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil, [email protected] 2 Departamento de Paleontologia e Estratigrafia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil Studies on foredunes mainly involve geomorphology, vegetation and human impact. The influences of other vertebrates in such harsh environment have been, so far, poorly studied. Ctenomys sp. is a solitary subterranean small rodent that inhabits sandy soils in South America. We studied the burrow system architecture of Ctenomys sp. communities from the foredunes of the Southern Brazil Coastal Plain by inserting plaster of Paris and excavating the tunnels. Ctenomys burrows are easy to find because of the mounds built by these animals on the foredunes. The structure of the burrow system is complex with several interlinked tunnels, occasionally open escape entrances, multiple chambers and turnarounds, unfinished tunnels, differences of slope (ramps), t-junctions and bifurcations. A specific, isolated, chamber is used as a latrine. Burrow entrances are open only when the rodent is taking out the sand or feeding. The tunnels have an average depth of 35 cm, being the deepest 55 cm and the most superficial 15 cm deep. The average burrow length ranges from 190 cm to 500 cm. The tunnels have different sizes varying from 6,7 9,3 cm wide and 6 11 cm high. The slope near the opening has ~28 o of inclination. In the central part of the burrows another slope occurs, with an inclination of ~38 o. In this part, the tunnel is narrower than in the rest of the burrow, with 8 cm wide and 6 cm high. The plaster molds sometimes preserve claw marks of 3 digits with up to 4 mm depth, usually occurring in sets of 4 excavation sequences. The surface area of the burrow systems is up to 5m 2. Some of the burrow systems appear to contain two levels, and/ or could be excavated over an abandoned burrow. Collapsed burrows are rapidly sealed to avoid the entrance of predators. In one of the collapsed tunnels a snake trace was found. Ctenomys sp., burrows provide a suitable microhabitat, used by the animals to protect themselves from adverse environmental conditions, particularly during winter when the wind impacts all the coastal area. Finally, the extensive interlinking tunnels provide underground routes to aboveground feeding sites and to escape from predators. 35

36 SLIC2013 Second Latin American Symposium on Ichnology Ichnology of deglaciation deposits from the Taciba Formation (Upper Carboniferous/Lower Permian, Paraná Basin) at Santa Catarina State (S Brazil) Dobler Lima, J.H. and Guimarães Netto, R. PPGeo, Universidade do Vale do Rio dos Sinos, São Leopoldo, Brazil, The shallow marine context influenced by deglaciation prevailed in the Paraná Basin during the deposition of the Itararé Group, which comprises, from base to top, the Lagoa Azul, Campo Mourão and Taciba formations. The Taciba Formation (Upper Carboniferous-Lower Permian) is a sedimentary succession composed predominantly of diamictites, shales and varve-like rhythmites. In Trombudo Central city (Santa Catarina State, southern Brazil), centimeter to decimeter thick siltstone and mudstone couplets (rhythmites) from the top of Rio do Sul Formation crop out, with disperse dropstones, very well preserved trace fossils and microbially induced sedimentary structures (MISS). The contact between the layers of siltstone and mudstone of each pair is sharp, but non-erosive, and parallel lamination is the prevalent sedimentary structure. The faceted clasts are interpreted as ice-rafted debris. This work aims to characterize the ichnofauna of this area, trying to provide support for paleontological and paleoenvironmental interpretations. The thinner rhythmic layers contain a monospecific assemblage composed of Helminthoidichnites isp., a horizontal shallow trail that suggests grazing of wormlike organisms or arthropod larva. This ichnotaxon is also present in thicker rhythmites couplets, but in this case is associated with Mermia isp. (grazing vermiform trail) and Cruziana problematica (arthropod locomotion trail). This trace fossil association normally is preserved below MISS, suggesting a suite of undermat miners. A dense assemblage of arthropod trackways and resting impressions is preserved on MISS-bearing layers, with a predominance of large forms of Diplichnites isp. and Umfolozia isp., and subordinate Diplopodichnus isp. and Gluckstadtella isp. The ichnofauna recorded in this rhythmic succession indicates that arthropods were dominant components of the biota, being myriapod-like organisms, notostraca, and merostomata the potential tracemakers. The endobenthic fauna colonized the substrate after the development of MISS, feeding on them. The composition of undermat miners suite suggests freshwater conditions. The other ichnotaxa correspond to trackways and resting traces produced by an epibenthic fauna, whose scarcity of imprint details suggests preservation as undertracks. The trackways of myriapods (Diplichnites gouldi and Diplopodichnus biformis), whose preservation may have been favored by the presence of MISS, indicate that the substrate periodically underwent subaerial exposure. The well-preserved trackways in the studied succession are related, in the literature, to deglaciation deposits. Preliminarily, it can be inferred that the ichnofauna associated with the Taciba Formation rhythmites in Trombudo Central suggests colonization of very shallow water bodies or even of moist terrestrial substrates influenced by freshwater from glacier melting, in a glaciolacustrine context. 36

37 Abstracts and Intra-symposium Fieldtrip Bioerosión en Crepidula (Mollusca, Gastropoda) del Cuaternario marino de Argentina: interacciones bióticas con poliquetos (Annelida, Spionidae) Farinati, E.A. 1, Aguirre, M.L. 2, 3 y Richiano, S. 2, 4 1 Universidad Nacional del Sur, [email protected] 2 CONICET 3 Facultad de Ciencias Naturales, Universidad Nacional de La Plata 4 Centro de Investigaciones Geológicas, Conicet-UNLP Las concentraciones esqueléticas que conforman los depósitos litorales del Cuaternario marino de Argentina contienen, entre los componentes biogénicos mayoritarios, una rica malacofauna (principalmente gastrópodos y bivalvos) con abundantes signos de bioperforaciones. Distintos organismos (poríferos, poliquetos, briozoos, otros moluscos) del ambiente litoral original habrían actuado como agentes tafonómicos alterando la preservación y/o acelerando los procesos de destrucción de las conchillas, entre ellos la bioerosión por distintas actividades (alimentación, habitación, pastoreo, locomoción). En muestras de depósitos costeros originados durante el proceso transgresivo-regresivo del Holoceno medio se analizaron bioperforaciones sobre conchillas del gastrópodo Crepidula, taxón con mayor frecuencia de signos de bioerosión entre la totalidad de moluscos recuperados a lo largo del área costera, entre el margen del Río de La Plata y sur de la provincia de Santa Cruz. Se puso especial énfasis en C. aculeata una de las especies más constantes y dominantes en el Holoceno marino, tanto del sector bonaerense como patagónico, con máxima tasa de bioerosión y buena calidad de preservación. De un total de conchillas de C. aculeata, 177 (16%) exhiben bioerosión sobre la superficie externa. Se calcularon porcentajes de ocupación preferida por parte de los organismos perforadores sobre el esqueleto del hospedador: 1) área central (66%); 2, lado derecho (17%); 3, ápice (12%); 4) margen ventral (5%). Las estructuras bioerosivas identificadas en las conchillas de C. aculeata son asignables a dos icnogéneros: Caulostrepsis (rango estratigráfico Devónico-Reciente) y Maeandropolydora (Triásico-Reciente), cuya frecuencia es 65% y 35%, respectivamente. Las trazas corresponden a túneles meandriformes, cuyos orificios de entrada y salida exhiben diferentes grados de proximidad (Caulostrepsis) o separación (Maeandropolydora), y variaciones en el recorrido de los túneles. Desde un punto de vista etológico, ambos icnogéneros se atribuyen a búsqueda de refugio (Domichnia). Las curvas de distribución acumulativas para el ancho máximo de la conchilla en especímenes perforados (177) y no perforados (901) son muy similares, indicando que el organismo productor no tenía una selección ontogenética preferencial del hospedador. La frecuencia máxima de perforaciones se ubica en la zona central y bordes, lo que concuerda con el hábito epifaunal gregario del género. Los productores, poliquetos de la Familia Spionidae, son bentónicos activos, errantes, típicamente perforantes de rocas y/o sustratos calcáreos. Se descarta una colonización post mortem. Las estructuras fueron producidas en vida del sustrato anfitrión (Crepidula) al estar localizadas exclusivamente en la superficie externa de las conchillas. Los Spionidae perforan preferentemente conchillas esculturadas con pequeñas espinas, raramente superficies lisas. Ello explica el arreglo de los túneles en las zonas más ornamentadas de la especie (centro y bordes). Los anélidos se habrían refugiado en sectores más protegidos de la conchilla y óptimamente situados en la interfase agua- sedimento. Maeandropolydora y Caulostrepsis testimonian indirectamente la presencia de poliquetos que no se registran como fósiles de cuerpo dado su bajo potencial de fosilización, indicando interacciones bióticas entre gasterópodos y anélidos que de otro modo no aparecerían en el registro fósil. 37

38 SLIC2013 Second Latin American Symposium on Ichnology Ichnological study of the Lower Cretaceous Mulichinco Formation (Neuquén Basin, northern Patagonia): preliminary results Fernández, D.E. and Pazos, P.J. Instituto de Estudios Andinos Don Pablo Groeber (IDEAN CONICET). Depto. de Ciencias Geológicas, FCEN, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina, The Mulichinco Formation (Mendoza Group, Neuquén Basin) is a mainly siliciclastic succession of early Valanginian age exposed in the Neuquén province (Argentina), in the area between the Agrio River to the south and the limit with the Mendoza Province to the north. Previous research conducted in this unit reported the presence of several ichnotaxa. However, the focus of those analyses was mainly sedimentological and/or stratigraphical. During the past few years, the first extensive ichnological study of this unit has been carried out. Along with the work on trace fossils, sedimentological characteristics have been considered in the study. The aim of this work is to communicate some preliminary results. In the central and northern sectors of the Neuquén Province, where the deposits of this unit are mainly marine, four localities along the north-south directed National Route 40 were analyzed in detail. The material has been so far assigned to following ichnotaxa: cf. Arenicolites Salter, Asteriacites lumbricalis von Schlotheim, Bolonia lata Meunier, Chondrites?intricatus (Brongniart), Cochlichnus anguineus Hitchcock, Gyrochorte comosa Heer, cf. Rhizocorallium Zenker, Lockeia siliquaria James, cf. Nereites MacLeay,?Ophiomorpha isp., Ophiomorpha nodosa Lundgren, Palaeophycus tubularis Hall, cf. Planolites Nicholson, Rosselia socialis Dahmer, Skolithos verticalis Hall, Teichichnus isp.,?thalassinoides isp. and cf. Treptichnus Miller. Three types of trace fossils have been described using open nomenclature: arthropod trackways, tetrapod swimming traces and escape structures. The ichnofossils were described and their distribution along the unit carefully noted. Fourteen types of trace fossils have been added to the previously known ichnodiversity of the Mulichinco Formation. Preliminary results of the sedimentological studies show that in some localities tidally-dominated depositional settings were more widespread than reported in prior studies. Also, in some localities the inferred paleoenvironment for the top of the unit is shallower than previously thought. The ichnological characteristics show that these deposits bear complex ethological and paleodiversity information. The new sedimentological information gathered is important for revising paleoenvironmental reconstructions. 38

39 Abstracts and Intra-symposium Fieldtrip Asteroid trace fossils from a Lower Cretaceous shallow marine paleoenvironment in Patagonia: the first record of starfishes for the Agrio Formation Fernández, D.E. 1, Pazos, P.J. 1, Pérez, D.E. 2 and Luci, L. 1 1 Instituto de Estudios Andinos Don Pablo Groeber (IDEAN CONICET). Depto. de Ciencias Geológicas, FCEN, Universidad de Buenos Aires. Ciudad Autónoma de Buenos Aires, Argentina, [email protected] 2 Museo de Cs. Naturales Bernardino Rivadavia, Ciudad Autónoma de Buenos Aires, Argentina Body fossils of any group of starfish are seldom preserved, since the discrete skeletal elements (ossicles) most commonly dissarticulate after death. Many fossil asteroid examples are known either from one single sample or from a single bed containing more than one specimen. Several reports worldwide have attributed trace fossils to ophiuroids. In contrast, asteroid trace-fossil occurrences are scarcer and mostly restricted to a few Triassic and Jurassic examples. Fossil asteroids in general are uncommon in South America. In the Neuquén Basin, asterozoan trace fossils (assigned to Asteriacites lumbricalis and attributed to ophiuroids) are known from the Mulichinco Formation (early Valanginian, Mendoza Group). The only fossil asteroid known in the entire basin comes from that unit and was described as an astropectinid (Asteroidea, Neoasteroidea, Paxillosida, Astropectinidae). Given the patchy body fossil record of asterozoans in the Neuquén Basin (Patagonia), the finding of asteroid trace fossils is important in the reconstruction of its paleontological framework. The material presented in this work comes from the type locality of the Agrio Formation (late Valanginian early Barremian, Mendoza Group). These specimens represent the first record of starfishes for this unit. The aim of this work is threefold: i) to report the existence of these specimens, taking into account that the ichnospecies they were assigned to has not been found prior to this study in deposits of Cretaceous age; ii) to describe the trace fossils and discuss their producers along with some paleoecological and taphonomic inferences; and iii) to provide a more accurate paleoenvironmental context than previously reported. The Agua de la Mula Member or Upper Member of the Agrio Formation is a Late Hauterivian Early Barremian mixed carbonate siliciclastic marine and marginal-marine succession. Previous workers have interpreted the upper part of the Agrio Formation as shallow subtidal to proximal offshore deposits influenced by fair weather and storm waves. In the study site, the uppermost part (63 m) of the Agua de la Mula Member represents a paleoenvironment evolving from marine to marginal-marine, including tidal flat deposits with high and/or fluctuating salinity. The interval studied begins at m above the base of the unit and ends with an ooliticskeletal bar. Two main facies are recognized. The asteroid trace fossils were found in facies 2. The logged section included in this work represents upper shoreface to upper foreshore deposits. The inferred paleoenvironment is therefore shallower than previously reported. The trace fossils are shallow, star-shaped burrows preserved as negative epirelief. They are approximately 10.5 cm in total diameter. Five axes radiate from a 3 cm wide central area. These are straight, with a broad base and distally tapering. Their width varies, and some of the tips are diffuse. These depressions display irregular ornamentation in the shape of discontinuous, small bulges, without any transverse striae. Given their diagnostic features, these trace fossils are assigned to Asteriacites cf. quinquefolius. The most plausible producers are, in this case, asteroids belonging to the family Astropectinidae. These starfishes are semi-infaunal, capable of self-burial in soft substrates, sometimes with a feeding purpose. These ichnofossils could be associated with: i) a non-sustained resting behavior (cubichnia) with shallow burial; ii) a more temporally prolonged shallow burial, typical of a semi-infaunal life style; iii) an active search for prey within the uppermost centimeters of the substrate; or iv) a combination of behaviors. 39

40 SLIC2013 Second Latin American Symposium on Ichnology Occurrence of small Ophiomorpha from various early Miocene formations of Hungary Fodor, R. Mátra Muzeum, Gyöngyös, Hungary, Ophiomorpha-like trace fossils have been found at two early Miocene age localities in North- Hungrary. Their size is quite similar to Ophiomorpha puerilis Gibert, Netto, Tognoli and Grangeiro, 2006, which were described from the Pleistocene of southern Brasil. But their morphology differs significantly from the known Ophiomorpha ichnospecies. The first locality is Diósgyor, at the northern part of Miskolc at North- Hungary. There is an up to 300 m long abandoned sandpit at the northern part of the town which exposes a 20 m thick sandy-silty part of the Salgótarján Lignite Formation. This formation is an Early Miocene coal-bearing series, which occurs widespread in the Borsod Basin at North-Hungary. The general sedimentological character of the coal-bearing deposits reflects a shallow-marine siliciclastic succession of 25 high-order parasequences. The silty facies represents lower-shoreface environments of the transgressive periods (TST), while the thick, locally sharp-based sandstone have dominantly been deposited in the upper shoreface, associated with forced regressions (FSST). Greyish sandstones contain the Ophiomorpha-like trace fossils. At the middle part of the quarry the small Ophiomorpha is the dominant trace fossil at the top of the layer. Other common trace fossils are Planolites isp. and Thalassinoides isp. These trace fossils show transition between Cruziana and Skolithos ichnofacies at the lower part of the upper shoreface environment. The second locality a former sandpit is situated at the boundary of Bükk and Uppony Mountains in the vicinity of the village Dédestapolcsány. The sediments of the exposure belong into the Garab Schlieren Formation. The sandpit can be divided into four well-recognizable sedimentological units. Each unit has special trace fossil assemblage. The fourth unit; the uppermost part of the sandpit, is a 3 m-thick cross-stratified limonitic sandstones poor in trace fossils. Rare occurrence of Ophiomorpha isp. and Teichichnus isp. can be observed. The Ophiomorpha-like trace fossils are characterized by very thin tunnels with small, round pelloidal noodles in their walls. The burrow cross-section is rounded or elliptical. Their diameter is between 2 and 5 mm. The walls are covered by rounded pellets, which are 0.5 to 0.75 mm in diameter. The burrows are also filled by pellets of same size. The position of the trace fossils is vertical and situated parallel to each other. The tunnels are straight. No forks or bifurcations had been observed. There are sand grains inside the pellets in most cases. These sand grains could be originated from the surrounding sediment. The above mentioned morphological characteristics could suggest that the traces belong to the Phymatoderma group. 40

41 Abstracts and Intra-symposium Fieldtrip Icnofósseis associados à fauna de Ediacara da Bacia do Jaibaras (Nordeste do Brasil) Gomes Barroso, F.R. 1, Sales Viana, M.S. 2, Agostinho, S. 1 and Ferreira De Lima Filho, M. 1 1 Universidade Federal de Pernambuco-UFPE/ Laboratório de Geologia Sedimentar e Ambiental-LAGESE, Recife-PE, Brasil, [email protected] 2 Universidade Estadual Vale do Acaraú/Laboratório de Paleontologia/Museu Dom José, Sobral-CE, Brasil Recentemente foram apresentados fósseis típicos da fauna Ediacarana na Bacia do Jaibaras, região noroeste do Estado do Ceará, incluindo as seguintes espécies: Charniodiscus arboreus;?charniodiscus concentricus; Cyclomedusa davidi; Ediacaria flindersi; Medusinites asteroides; Kimberalla quadrata; Palaeoghragmodictyon reticulata; e Parvancorina minchami. A biota de Ediacara representa o aparecimento dos primeiros organismos com arquitetura complexa na história da Terra, no período Ediacarano, e pela primeira vez, apareceram marcas nos sedimentos seguramente produzidas por animais diferentes dos representantes ediacaranos, ou seja, os icnofósseis. Há evidências de que muitos icnotaxons surgiram antes da explosão cambriana, com exemplos de escavações feitas por animais triproblásticos até mesmo em rochas mesoproterozoicas, embora haja um consenso que a maioria dos icnofósseis apareceram por volta de 550 Ma. Os icnofósseis estão incluídos na Bacia do Jaibaras, numa unidade estratigráfica denominada informalmente de Arenito Contra Fogo, por não possuir qualquer semelhança com as formações Massapê, Pacujá e Aprazível, que juntas compõem o Grupo Jaibaras. Foram identificados três icnogêneros: Arenicolites - escavações em forma de U, simples, sem spreite, orientadas perpendicularmente à estratificação; Palaeophycus - escavações intraestratais retas a levemente curvas, ligeiramente onduladas a flexuosas, de superfícies lisas cilíndricas e dispostas horizontalmente à estratificação; e Planolites - escavações meandrantes de orientação horizontal a oblíqua em relação à estratificação, podendo entrecruzar-se, raramente ramificadas, com dimensões e configurações variadas, apresentando seção transversal circular à elíptica. É confirmada a presença de Arenicolites no Neoproterozoico, descrito em conformidade com as taxobases propostas para este icnogênero, além disso, sua associação com Planolites e Palaeophycus elimina qualquer possibilidade de ser uma estrutura sedimentar. Palaeophycus já foi descrito na Grande Bacia dos Estados Unidos junto a representantes Edicaranos. Planolites é considerado um dos icnogêneros que aparece no Neoproterozoico e permanece no Fanerozoico, sendo descrito no Uruguai, numa sequência vulcano-sedimentar relacionada ao Ciclo Brasiliano, bem como abaixo do limite Neoproterozoico-Cambriano do Canadá. A maneira em que o sedimento foi deslocado sugere que o mesmo havia sido pressionado em vez de manipulado por qualquer órgão especializado em remover o sedimento. O ambiente deposicional foi atribuído a um sistema flúviodeltáico com ingressão marinha e a idade relativa dos fósseis Ediacaranos foi sugerida em, pelo menos, 560 Ma. Contudo, a associação dos icnofósseis atesta a transição Ediacarano-Cambriano, e todo o conjunto de fósseis se assemelha à Assembléia White Sea típica da Austrália e Rússia. Portanto, aqui surge mais um evidência de que as relações ecológicas complexas e os verdadeiros bilaterianos já estavam presentes no Neoproteozoico. 41

42 SLIC2013 Second Latin American Symposium on Ichnology Bioerosión en ostrácodos de sedimentos holocenos del estuario de Bahía Blanca Kihn, R.G. 1 y Gómez, E.A. 1, 2 1 Instituto Argentino de Oceanografía. Bahía Blanca, Argentina, [email protected] 2 Universidad Tecnológica Nacional FRBB. Bahía Blanca, Argentina En este trabajo se analizan las evidencias de bioerosión en poblaciones de ostrácodos holocenas del testigo KP60Bis (39º S-61º ), ubicado en la parte externa del estuario de Bahía Blanca. Los ostrácodos constituyen una de las posibles presas de distintos grupos acuáticos, tales como gasterópodos, bivalvos carnívoros, escafópodos, equínidos, peces o incluso otros ostrácodos (p.e., Leal, 2008). Si bien en el registro fósil las evidencias de depredación en sus valvas y caparazones se han detectado desde el Cámbrico, los antecedentes argentinos son escasos. Los distintos tipos de perforaciones observadas se han atribuido a la acción depredadora de diversos invertebrados. El testigo se muestreó cada 10 cm, las muestras se tamizaron con un tamiz de maya 63 µm y luego se secaron en estufa a 50ºC. Se extrajo el total de valvas y caparazones presentes, para este trabajo se consideraron sólo las valvas que presentaron perforaciones. Las especies de ostrácodos con bioerosión fueron: Loxocythere variasculpta, Loxoconcha paranensis, Neocytherideis ruidis y Cytheretta punctata. Las perforaciones halladas en las valvas de los ostrácodos fueron asignadas al icnogénero Oichnus. La perforación atraviesa el sustrato cuando éste es una conchilla fina; de lo contrario termina dentro de él como una depresión, o como una perforación corta y subcilíndrica. Se puedieron diferenciar dos tipos de perforaciones: 1.- Oichnus simplex: incluye perforaciones cilíndricas, con abertura interna y externa de diámetro similar, con un diámetro que oscila entre los 0,25 mm y 1 mm. 2.- Oichnus paraboloides: perforaciones de sección circular o subcircular, con su eje de penetración más o menos perpendicular a la superficie del sustrato. Del análisis de 15 ejemplares se obtuvo que el diámetro mayor (externo) oscila entre 0,30 mm y 1 mm; y el diámetro menor (interno) entre 0, 17 y 0,6 mm. Además se tomó el alto de las valvas en proporción al diámetro de la perforación. Cada valva perforada presenta una única perforación. El análisis de los diagramas de Pope indicó una concentración preferencial de estas perforaciones en las zonas central y anterior de las valvas. Las evidencias de depredación son muy escasas en las muestras analizadas, con solo 8 valvas perforadas de un total de valvas y caparazones separados (0,37 %). Los dos tipos de perforaciones distinguidos parecen corresponder al ataque de distintas familias de gasterópodos. El mayor porcentaje de depredación se registra en los ambientes de baja energía con un alto grado de nutrientes disponibles y con una mayor densidad de ostrácodos. Probablemente los factores que influyen en la depredación de la fauna de ostrácodos sean: el desarrollo de las poblaciones, la energía ambiental y la disponibilidad de nutrientes. 42

43 Abstracts and Intra-symposium Fieldtrip Una icnita humana del Pleistoceno tardío, Sitio Arqueo-paleontológico Pilauco, Región de Los Lagos, Osorno, Chile Macias, C., Moreno, K. y Pino, M. Universidad Austral de Chile, Instituto de Ciencias Ambientales y Evolutivas, Valdivia, Chile, [email protected] Una estructura sedimentaria del Pleistoceno tardío con morfología similar a una icnita humana fue encontrada en el sitio Pilauco, Osorno. Este sitio arqueo-paleontológico contiene abundantes restos de mega, macro y microfósiles, de fauna y flora extinta y actual. Se destacan huesos de Notiomastodon (= Stegomastodon) platensis, Hemiauchenia paradoxa, Equus (=Amerhippus) andium, Conepactus sp., Pudu sp., entre otros vertebrados; así como pelos aún no identificados; coprolitos con parásitos de rumiantes (probablemente équidos) e insectos coleópteros estiercoleros. Además, hojas, semillas y polen representativo de un bosque abierto de tipo Norpatagónico y vegetación acuática. También se han podido identificar materiales culturales correspondientes a artefactos líticos como raspadores y cortadores elaborados en obsidiana dacítica, basalto fino y cuarcita, desechos de talla y recorte, así como núcleos. Todos estos materiales provienen de la capa de turba denominada PB-7, correspondiente a un depósito pantanoso de una antigua planicie de inundación. Junto a este prolífico registro fósil se excavó una estructura sedimentaria de 27 cm de largo y 11 cm de anchura máxima, que por ser aislada no permite una identificación directa. Motivo por el cual se realiza la presente investigación para recopilar mayores antecedentes que aclaren su identidad. Dicha estructura fue encontrada durante la excavación de la cama de huesos fósiles al detectarse un cambio en la consistencia del sedimento, con el relleno más blando y fácil de excavar y más compacto en la capa portadora de la estructura sedimentaria. Para evaluar si esta estructura sedimentaria podría atribuirse a una icnita, descartándola como artefacto, y estudiar la posibilidad de atribuirla a un humano, realizamos: i) una descripción detallada de la morfología, composición, estratigrafía y textura sedimentaria; ii) obtuvimos fechas radiocabónicas locales de la secuencia y iii) realizamos huellas experimentales con 3 voluntarios a 3 diferentes grados de hidratación del sedimento portador. Los resultados sugieren que la estructura es una icnita ya las texturas son altamente distintivas entre el sedimento portador, que tiene mayor proporción de grava y limo, y el de relleno que contiene más materia orgánica. La estratigrafía de estas capas indica que estas fueron coherentemente depositadas y la datación sugiere que la huella debe haberse formado entre los y C años AP (~16,000 años calibrados AP). Estas fechas son contemporáneas a la datación de un trozo de cráneo de Notiomastodon que yacía a menos de un metro de la icnita (13.220±60 y ±35 años AP). Por otra parte, los experimentos en sedimento colmatado de agua fueron capaces de reproducir la morfología de la estructura sedimentaria, incluyendo la presencia de un intraclasto sedimentario en la parte distal de la impronta plantar que se produce por el arrastre y posterior caida de una porción de sedimento desde el hallux durante el movimiento del pie hacia delante; la zona distal del hallux alargada y la obliteración de la marca dejada por los dígitos laterales debido al colapso del barro. Todas estas características son reconocibles en la estructura sedimentaria, por lo que la evidencia permite sugerir que se trata de la icnita humana más antigua del sur de América del Sur. Siendo circa tres mil años más antigua que las de Monte Verde ( años calibrados AP). 43

44 SLIC2013 Second Latin American Symposium on Ichnology Tidal flats through time: the trace-fossil record of evolutionary innovations and faunal turnover Mángano, M.G. and Buatois, L.A. Department of Geological Sciences, University of Saskatchewan, Saskatoon, Canada, A comparison of tidal-flat ichnofaunas through geologic time allows distinction of five main evolutionary phases: (1) the initial invasion by animals (earliest Cambrian), (2) the arthropod expansion (Cambrian-Ordovician), (3) diversification and faunal turnover (Silurian-Devonian), (4) setting the stage for the Modern Fauna (Carboniferous-Permian), and (5) infaunalization and the role of crustaceans (Mesozoic-Cenozoic). This framework allows understanding the importance of tidal flats as sites of evolutionary innovations and the associated faunal turnover that took place in the intertidal realm through the Phanerozoic. Tidal-flat colonization started during the Fortunian, as revealed by the presence of monospecific suites of Treptichnus pedum in extremely shallow water. Later in the early Paleozoic, ichnologic data reveal the establishment of an intertidal fauna dominated by mollusk-like animals, euthycarcinoids and trilobites. Early Paleozoic tidal flats, and particularly Cambrian ones, were anactualistic in nature, reflecting reduced predation pressure, absence of terrestrially derived food and microbial binding. The rest of the Paleozoic witnessed faunal turnover, with the appearance of new tracemakers, and a consequent increase in ichnodiversity. In particular, bivalves became dominant in late Paleozoic tidal flats, including relatively deep-tier siphonate representatives. Mesozoic-Cenozoic tidal-flat ichnofaunas are dominated by deep-tier bioturbators, particularly crustaceans, as well as polychaetes and bivalves. The role of ecosystems engineers increased through the Phanerozoic, reaching a peak during this latter phase with active modification of the intertidal landscape by infaunal bioturbators. Global and alpha ichnodiversity both steadily increased through the Paleozoic. However, ichnodiversity of Mesozoic-Cenozoic tidal flats decreased with respect to Paleozoic levels. This pattern is regarded as a preservational bias, resulting from increased shallow-tier destruction by deep-tier key bioturbators in post-paleozoic times. 44

45 Abstracts and Intra-symposium Fieldtrip Early Permian vertebrate ichnology of the Southern Alps (N Italy): new discoveries and sites of interest Marchetti, L. 1, Avanzini, M. 2, Conti, M.A. 3 and Santi, G. 1 1 Dipartimento di Geoscienze, Università degli Studi di Padova, Padova, Italy, [email protected] 2 MUSE, Museo delle Scienze, Trento, Italy 3 Università La Sapienza di Roma, Dipartimento di Scienze della Terra, Roma, Italy The Permian vertebrate ichnology of the Southern Alps has been investigated since the 19th century, but the major interest of researchers was on the Late Permian ichnofauna, a unique example worldwide, and less importance was given to the Early Permian one. Only few works treat specifically ichnology of this period and their significance is linked to the scientific knowledge of the time, to the provenance of the material and to the different perspectives of the authors. This fact implies an underestimation of Early Permian tetrapod ichnology of the Southern Alps, thus a serious work of revision was needed. The study of about 1000 specimens from various Italian collections, with homogeneous approach which follows the more recent developments in ichnology, bring us to reconsider the meaning and interest on the Early Permian Italian ichnofauna. The described material was restudied, new specimens were analyzed and new and historical sites were interested by field work. Two new ichnotaxa for the Southern Alps were recognized: Hyloidichnus bifurcatus and Limnopus heterodactylus, the other ichnogenera were confirmed (Dromopus, Amphisauropus, Erpetopus, Varanopus, Batrachichnus). The most striking feature of this Artinskian-Kungurian association is the lack of Dimetropus and Ichniotherium, ichnogenera widely diffused at the time. This could be explained with a stratigraphical hypothesis (they were declining or becoming extinct) or an environmental one (lacks of researches on alluvial fan and coastal plain settings). The association lists the same forms in the Collio and Orobic basins (although in different proportions), instead fossils from the epiclastic units of the Athesian Volcanic Complex (Tregiovo, Monte Luco) are fewer and show a reduced ichnofauna (Dromopus, Amphisauropus, Erpetopus, cf. Varanopus, Hyloidichnus, cf. Batrachichnus). This seems to be clearly a bias, and not an evolutionary clue. The revision of the Camunipes cassinisi holotype and the study of new material allowed a real evaluation of the Erpetopus/Camunipes dualism, they clearly correspond to the same ichnogenus (Erpetopus), but some features permitted to distinguish two different ichnospecies. The Italian material offers new perspectives on the systematics of captorhinomorph tracks, still debated and incomplete. Behavioral studies were conducted on new Amphisauropus specimens: the most striking features recognized are parallel locomotion with other tetrapods (Erpetopus) - Cima Bosco site, E Collio Basin- and a trackway with deep and continuous tail impression in a peculiar sinusoidal arrangement -Lake Inferno site, Orobic Basin-, this latter represents the first record worldwide. From these first results we can clearly affirm a renewed importance of the Early Permian vertebrate ichnofauna of the Southern Alps: the presence of well-preserved and adapted specimens permits behavioral and ichnotaxonomical studies, the study of ichnoassociation and facies allows stratigraphical and environmental interpretations, these latter would be certainly improved with a parallel evaluation of invertebrate ichnology, and much more has to be discovered. 45

46 SLIC2013 Second Latin American Symposium on Ichnology The Early Permian Gerola Valley ichnosite (W Orobic Basin, N Italy): taxonomical revision and paleoenvironmental reconstruction Marchetti, L. 1, Ronchi, A. 2 and Santi, G. 2 1 Dipartimento di Geoscienze, Università degli Studi di Padova, Padova, Italy, [email protected] 2 Dipartimento di Scienze della Terra e dell Ambiente, Pavia, Italy A taxonomical and behavioral study has been attempted on the historical Val Gerola section (Pizzo del Diavolo Fm.), which represents one of the best tetrapod ichnosite of the whole Southern Alps. With respect to previous studies the ichnoassociation is now enriched by the ichnogenera: Hyloidichnius, Erpetopus, Limnopus, cf. Batrachichnus. In addition, the exceptional preservation of Amphisauropus footprints allows inferences on behavior of such ichnotaxon. Field work permitted also to collect new data on invertebrate traces and plant remains, whose study is now in progress. A detailed facies analysis was concentrated mainly on the Pizzo del Diavolo Fm. topmost fine red lithofacies, just below the Verrucano Lombardo Fm., which revealed the most abundant fossil content. Facies description includes also insights on the lower grey-green alluvial lithofacies, which contains cineritic-like layers (petrographical and geochronological data in progress). The final aim of our study is i) the depositional, paleoenvironmental and climatic reconstruction of this sector of W Orobic Basin through an integration of paleontological data and detailed facies analysis, and ii) the regional correlation of this sector with other coeval ones of paleoeurope. 46

47 Abstracts and Intra-symposium Fieldtrip Diverse deep marine trace fossils from the Early Paleozoic metasedimentary rocks of the Las Lagunitas Formation, Frontal Cordillera, Argentina Melchor, R.N. 1, Cardonatto, M.C. 2, and Tickyj, H. 2 1 INCITAP (CONICET - Facultad de Ciencias Exactas y Naturales), UNLPam, Santa Rosa, La Pampa, Argentina, [email protected] 2 Facultad de Ciencias Exactas y Naturales, UNLPam, Santa Rosa, La Pampa, Argentina A high-diversity ichnofauna (17 ichnogenera and 20 ichnospecies) is reported from metasedimentary rocks of Late Ordovician to?silurian age from the Frontal Cordillera of Mendoza, Argentina. The Las Lagunitas Formation (about 800 m thick) includes four lithologic packages: 1) coarse- to medium-grained wackes interbedded with black shales containing graptolites of the Climacograptus bicornis biozone (Sandbian or Caradoc stage) overlain by 2) medium- to fine-grained sandstones. The later is in fault contact with 3) coarse- to medium-grained cross-bedded quartz sandstones and are conformably overlain by 4) a coarsening and thickening upward package composed of coarse- to fine-grained wackes with interbedded olive-green shale. The later package contains the ichnofossils described in this contribution. The specimens were collected at three localities of the Cordón del Carrizalito: Cañada Seca (34º S, 69º W), Arroyo Cortaderas (34º S, 69º W), and an unnamed locality (34º S, 69º W). The ichnofauna is dominated by structures essentially developed in the horizontal plane including Nereites ispp., Phycodes bilix, Zoophycos isp., Lophoctenium isp. and Helminthoidichnites tenuis occurring in olive green shales interbedded with graded sandstone of turbiditic origin. Subordinate ichnotaxa in the same facies include: Palaeophycus tubularis, Protovirgularia dichotoma, Treptichnus bifurcus, Phycosiphon incertum, Chondrites isp., Glockerichnus isp., Saerichnites isp., Cosmorhaphe isp., and? Dictyodora isp. Parallel-aminated or cross-laminated siltstone contains?archaeonassa isp., Teichichnus isp., and Monocraterion isp. No trace fossils were recovered from turbidite soles, which is probably a sampling bias. Nereites, the more abundant ichnogenus, is represented by four ichnospecies: N. macleayii, N. cambrensis, N. jacksoni, and Nereites isp. N. macleayii appears as submillimetre furrows with similarly sized lobes arranged perpendicular to the central furrow, which cover entire laminae and display a thigmotactic arrangement, with a curved or spiral pattern. Nereites cambrensis is usually larger, with a winding pattern and with pointed sediment lobes arranged at an acute angle with the central furrow. Nereites jacksoni is characterized by larger rounded lobes. Nereites isp. include specimens that correspond to Neonereites uniserialis and N. multiserialis preservational variations. Phycodes bilix is a bundle of horizontal, slightly curved and rarely bifurcated cylindrical burrows that converge in the proximal zone and diverge distally. The specimens assigned to Zoophycos isp. have horizontal U or J-shaped spreiten and local preservation of the central tube. Lophoctenium isp. is characterized by a horizontal lobate trace with U-shaped burrows and secondary comb-like burrows. The dominance of Nereites and rarity of graphoglyptids make the assemblage comparable with early Silurian trace fossil assemblages from New Brunswick (Canada) and Maine (USA), and also probably with Ordovician trace fossils from the Barrancos region of Portugal. Although a sedimentological framework is lacking, the trace fossil association can be compared with the Nereites Ichnosubfacies suggesting a lobe fringe setting and well-oxygenated pore waters. 47

48 SLIC2013 Second Latin American Symposium on Ichnology Beetle burrows with a terminal chamber across a modern river valley: an example from the southern Poland Mikuś, P. 1 and Uchman, A. 2 1 Institute of Nature Conservation, Polish Academy of Sciences, Kraków, Poland, [email protected] 2 Institute of Geological Sciences, Jagiellonian University, Kraków, Poland Ground beetles (Coleoptera: Carabidae) of the genera Bembidion and Harpalus and the scarab beetles of the genus Melolontha (Coleoptera: Melolonthinae: Scarabaeidae) produce chambered burrows in modern alluvial sediments. They have been studied in the moderate climate zone of the Northern Hemisphere in the Dunajec river valley, southern Poland, during a few seasons ( ). A few tens of wax-stearine and plaster-of-paris casts of the burrows have been prepared. Bembidion and Harpalus produce domichnial and domichnial-fodinichnial burrows, respectively, and Melolontha (may bug or cockchafer) is responsible for pupichnial burrows. They occur in sandy to muddy non-vegetated or partly vegetated substrate on a well-drained, rarely flooded alluvial plain. The burrows display a characteristic morphology, which shows a straight or curved shaft and a horizontal to oblique terminal chamber. The Bembidion and Harpalus burrows are similar but they show a wide range of morphological variability, including forms in which the terminal chamber is poorly developed. Their inclination changes from oblique (most common) on horizontal surfaces to horizontal in steep scarps of the river bank. The Melolontha burrows are larger, with vertical shafts and strongly elongated chambers, which longer axis is perpendicular or oblique in respect to the shaft. The Melolontha and Harpalus burrows (less than 1 burrow per m 2 ) occupy more vegetated areas in more distal areas, including higher river terraces. The Bembidion stephensii burrows (up to 5 per m 2 ) occur in the intermediate, less vegetated environments with respect to the river channel, while the Bembidion quadrimaculatum is present in more proximal, non-vegetated or poorly vegetated flood plain (5 burrows per m 2 ) and scarps of the river channel (up to 100 burrows per m 2 ). Number of the burrows is strongly controlled by the water level. Every flood kills most of the tracemakers. After stronger flood, some tracemaker populations do not restore during the same season. Burrowing activity of the beetles is reduced in late autumn and is stopped during winter, then usually frost and snow appear. The studied burrows are similar to the trace fossil Macanopsis, which is known from marine (at least from Mesozoic) and non-marine environments (since the Devonian). Ground beetles and scarab beetles should be considered as possible tracemakers of continental Macanopsis, along with spiders, wasps, bees, cicada nymphs or millipedes, as presented in the literature. The studied burrows occur in environmental conditions typical of the Coprinisphaera Ichnofacies, mainly in poorly developed soils above the ground water table. A. Uchman was supported from the grant N N (Ministry of Sciences and Higher Education, Poland) in years

49 Abstracts and Intra-symposium Fieldtrip Huellas de dinosaurios en Colombia: revisión y nuevos hallazgos Moreno Sánchez, M. y Gómez-Cruz, A. de J. Universidad de Caldas, Departamento de Ciencias Geológicas, Manizales, Caldas, Colombia, [email protected] El hallazgo de las primeras huellas de dinosaurios en Colombia data de mediados del siglo XIX, cuando Carl Degenhardt reconoció rastros de aves (en realidad dinosaurios terópodos) en rocas mesozoicas en cercanías de Oiba (Departamento de Santander), siendo este reporte el primero en Latinoamérica. Recientemente se reconocieron rastros de Terópodos y ornitópodos en los alrededores de Chiquiza (Boyacá) en rocas de edad cretácica temprana. Estos rastros se hayan sobre superficies de areniscas continentales del La Formación Arcabuco. Adicionalmente se cita el hallazgo de huellas tridáctilas de dinosaurios carnívoros en una cantera cerca de la población de Alpujarrañ estas huellas datan del Cretácico Temprano (Barremiano?). En la misma unidad (Formación Alpujarra) se hallaron rastros de un posible ornitópodo en la región de Aipe (Huila). La exploración de unidades jurásicas dio como resultado el hallazgo de rastros de ornitópodos sobre areniscas tobáceas de la Formación Saldaña, en el río Venado (Departamento del Huila). En esta formación de origen continental se habían reportado rastros de cocodrilomorfos (Batrachopus sp.) y huellas de dinosaurios en areniscas rojas de la Formación Girón, en cercanías a Zapatoca (Santander). Las huellas de terópodos en calizas de la Formación Paja (Aptiano) de Villa de Leiva (Boyacá) no han sido mencionadas aún en la literatura. Los reportes de rastros de dinosaurios en Colombia son escasos pero posiblemente con una mayor exploración se pueda llenar este gap importante para comprender las rutas de migración de dinosaurios entre Norte y Sudamérica. 49

50 SLIC2013 Second Latin American Symposium on Ichnology Huellas de vertebrados en dunas costeras del Pleistoceno superior de Gibraltar (S de la Península Ibérica) Muñiz, F. 1, Cáceres, L.M. 2, Rodríguez-Vidal, J. 2, Finlayson, C. 3, Fa, D. 3, Finlayson, G. 3, Abad, M. 2 y Ruiz, F. 2 1 Facultad de Ingeniería, Geología, Universidad Andrés Bello, Talcahuano, Concepción, Chile, [email protected] 2 Depto. de Geodinámica y Paleontología, Univ. de Huelva, Huelva, España 3 The Gibraltar Museum, Gibraltar Los depósitos eólicos pleistocenos registrados en el Peñón de Gibraltar (S Península Ibérica) alcanzan notables espesores sedimentarios, localizándose como relleno de sus cuevas marinas, como los de Gorham s y Vanguard Caves, o en sus escarpadas laderas como la de Catalan Bay donde está registrada una de las Formaciones más importante y significativa de estos depósitos, la Catalan Sands. Ésta está constituida por sistemas de dunas de pie de acantilado y rampantes, que forman una rampa arenosa de 35º de pendiente, 1 km de longitud, altitud de 300 m y compuestas por arenas moderadamente bien clasificadas, poco carbonatadas y débilmente cementadas. En relación con la cronología de esta formación eólica, se han realizado dataciones OSL en sus tramos basales que han proporcionado una edad comprendida entre 130±15 ka, y 95±9 ka (estadio isotópico 5). Por su parte, existen otras dataciones que se podrían relacionar con la elaboración de la rampa de arena, la cual podría coincidir con el relleno de la Cueva de Ibex, cuyo relleno ha sido datado entre 49,4±3,2 y 37,1±3,3 ka. Todo el conjunto arenoso representa, por tanto, un registro morfosedimentario de los estadios MIS 5 a 2. En Catalan Bay, la exposición en secciones transversales de parte de estas dunas, permite la observación de su arquitectura y ordenación interna detallada de las laminaciones, dispuestas en sets de 2 a 3 m de espesor y estratificaciones cruzadas en surco y tabulares. Son en estas laminaciones donde se han reconocido 5 morfotipos de huellas, con un grado de conservación pobre debido a la naturaleza poco cementada del sustrato, a modo de secciones transversales verticales e hiporrelieves convexos, que se relacionan con la actividad de vertebrados mamíferos terrestres posiblemente pertenecientes a Proboscidios o Ceratomorfos, Artiodáctilos, Carnivora y Homínidae?. La afinidad entre huellas y productores, se ha establecido tomando como base los parámetros medidos, la forma de las huellas, su discusión con huellas similares descritas en la bibliografía y correlación con la fauna fósil de vertebrados descrita para el Pleistoceno superior de Gibraltar. 50

51 Abstracts and Intra-symposium Fieldtrip Trazas cruzianiformes producidas por espáridos actuales en el Estuario del Río Piedras (Lepe, Huelva, SO España) Muñiz, F. 1, Cárcamo, C. 1, Belaústegui, Z. 2, Domènech, R. 2 y Martinell, J. 2 1 Facultad de Ingienería, Geología, Universidad Andrés Bello, Concepción, Chile, [email protected] 2 Departament d Estratigrafia, Paleontologia i Geociències Marines, Universitat de Barcelona, Barcelona, España Los estudios de trazas recientes relacionados con la alimentación de peces sobre el hiperbentos costero-marino, son relativamente escasos. En general, se han descrito como depresiones someras simples (alargadas o cilíndricas) para peces gadiformes, notacanthiformes y batoideos, o compuestas (cilíndricas y adyacentes a otras con forma de medialuna ) para acipenseriformes. En este estudio, se presentan trazas de alimentación de los peces perciformes Diplodus vulgaris y Lithognathus mormyrus (Familia Sparidae) observadas en la zona intermareal y esteros del Estuario del Río Piedras, Lepe, SO España. En general, la morfología de estas trazas consiste en pequeñas depresiones bilobuladas, alongadas en la horizontal, muy someras verticalmente y con sección longitudinal ligeramente cóncava o más penetrantes hacia su parte distal. La bilobulación consiste en dos surcos separados por una pronunciada cresta central orientada longitudinalmente, en la base de los cuales se observan otras crestas mucho menos resaltadas, también rectas, paralelas entre sí y a la principal. Las trazas suelen aparecer aisladas u ocasionalmente contiguas en zigzag y se interpretan como el producto de la alimentación de D. vulgaris y L. mormyrus mientras pacen o depredan sobre el hiperbentos. La morfología resultante está directamente condicionada por la relación entre las primeras fases ontogenéticas (alevín-juvenil), el desarrollo dentario (carda-incisivos) y el trofismo (fitófagozoófago). Por otro lado, en el registro fósil hay descritos los icnogéneros, Piscichnus y Osculichnus, relacionados con un comportamiento alimentario de peces. Las morfologías de éstos distan mucho de la descrita para las trazas aquí estudiadas (cruzianiformes), que si quedaran representadas en el registro fósil, podrían ser atribuidas o confundidas con icnotaxones bilobulados, como el icnogénero Cruziana, comúnmente relacionado con la locomoción de artrópodos. 51

52 SLIC2013 Second Latin American Symposium on Ichnology Laguna del Monte, un nuevo yacimiento paleoicnológico del Pleistoceno tardío (Piso/Edad Lujanense), Guaminí, provincia de Buenos Aires (Argentina) Oliva, C. 1, Arregui, M. 1, Lirusso, V. 1 y de Valais, S. 2 1 Centro de Registro del Patrimonio Arqueológico y Paleontológico (CRPAP); Dirección Provincial de Patrimonio Cultural (DPPC); Instituto Cultural de la provincia de Buenos Aires (ICPBA), La Plata, Buenos Aires, Argentina. [email protected] 2 CONICET. Instituto de Investigación en Paleobiología y Geología. Universidad Nacional de Río Negro, Fisque Menuco (General Roca); Río Negro, Argentina Se reporta un nuevo yacimiento paleoicnológico ubicado en el margen sudoriental de la Laguna del Monte (Guaminí, provincia de Buenos Aires). El mismo comprende una reducida franja de aproximadamente km 2 de superficie, de 2.25 km de longitud por 0.1 km de anchura máximo expuesto. El relevamiento del sitio se inició en 2012 como respuesta a la denuncia efectuada por la Municipalidad de Guaminí ante la Dirección Provincial de Patrimonio Cultural, que oficia como autoridad provincial de aplicación de la Ley Nº 25743/03, de Protección del Patrimonio Arqueológico y Paleontológico e impulsa acciones tendientes al registro y puesta en valor de los bienes arqueológicos y paleontológico del territorio bonaerense. Los niveles portadores de las trazas, de base desconocida, conforman una potente sucesión de limolitas arenosas y fangolitas verde amarillentas (Asociación de Facies 1: AF1), finamente laminadas o con estratificación tabular planar; en las superficies de estratificación es frecuente la presencia de ondulitas subácueas y grietas de desecación. Una característica notable, presente en la casi totalidad de la superficie expuesta, es la presencia de una capa de actividad microbiana o biofilm. Se interpreta a estos depósitos como generados en un medio lacustre somero, probablemente situado en el área de transición entre los ambientes subácueo y subaéreo. Dentro del paquete sedimentario se intercalan limos arenosos castaño rojizos (Asociación de Facies 2: AF2), de constitución predominantemente masiva o con estratificación difusa sectorizada, los cuales se encuentran fuertemente bioturbados, culminando hacia el techo en varios niveles de paleosuelos superpuestos. Estos depósitos, los cuales adquieren gran importancia en dirección al continente, se habrían acumulado en un medio eólico sujeto a procesos pedogenéticos. La sucesión estratigráfica considerada es correlacionable con los términos basales de la Formación Luján (Pleistoceno tardío: Piso/Edad Lujanense) conocidos formalmente como los miembros Guerrero (AF1) y La Chumbiada (AF2). Las icnitas de vertebrados se presentan aisladas o conformando breves rastrilladas, y en algunos sectores exhiben un alto grado de superposición y se disponen de manera desordenada, careciendo el conjunto de una orientación general. De esta manera, las plataformas sedimentarias constituyen verdaderos pisaderos muy probablemente formados a orillas del lente ácueo. La icnofauna proveniente de estos niveles incluye una rica asociación de icnotaxones, que se comparte casi en su totalidad con la icnoasociación de las localidades de Pehuen- Có, Monte Hermoso y alrededores. Los icnotaxones están vinculados principalmente con los grupos taxonómicos Mammalia y Ave. La mayoría son huellas mamalianas, las que corresponderían a las icnoespecies: Neomegatherichnum pehuencoensis, Mylodontidichnum rosalensis, Acugnaichnum dorregoensis, Eumacrauchenichnum patachonicum, Lamaichnum guanicoe, Megalamaichnum tulipensis, Odocoileinichnum commune, Stegomastodon-ichnum australis e Hippipeda isp. Las huellas avianas están representadas por ejemplares comparables a Phoenicoptherichnum isp. y al menos tres tipos de improntas tridáctilas anisodáctilas (aún no denominados formalmente), uno de ellos probablemente vinculado con Charadriiformes y otros dos con Struthioniformes; las diferencias observadas entre los morfotipos asignados a este último orden, especialmente relacionadas con el grosor de los dígitos, probablemente se vinculen con distintos estados preservacionales dentro de un mismo icnotaxón. La icnodiversidad de vertebrados, la alta densidad de paleoicnitas y la presencia de más de un nivel sedimentario portador, hacen de este sitio un yacimiento de notable interés paleoicnológico. 52

53 Abstracts and Intra-symposium Fieldtrip Insect trace fossils in Middle and Late Triassic vertebrate bones: ancient dermestid and termite activity? Paes Neto, V.D., Pretto, F.A., Quezado de Figueiredo, A.E., Francischini, H., Soares, M.B. and Schultz, C.L. Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil, [email protected] Bone modification produced by insects is commonly recorded in Mesozoic and Cenozoic vertebrate fossils. The oldest insect trace fossils dates to the Middle Triassic on a dicynodont humerus from Santa Maria 1 Sequence, Paraná Basin, Rio Grande do Sul, southern Brazil, belonging to the Dinodontosaurus Assemblage Zone (AZ). We report new insect trace fossils in materials recovered from younger layers of the Santa Maria 1 and 2 Sequences. Some patterns are consistent with recent and putative fossil traces of dermestid beetle activity on vertebrate bones. These specimens were carefully prepared and observed at different light angles on a magnifying glass and some with CT scans. All analyzed ichnofossils were filled with sedimentary matrix, indicating that they were produced prior to burial. One trace fossil was found on a femur of a well preserved Middle Triassic (Santacruzodon AZ) proterochampsian Chanaresuchus bonapartei (UFRGS-PV T) that presents a 3 mm wide, ovoid pit mark on the distal epiphyses. The two specimens of the Hyperodapedon AZ (Late Triassic) collected on the Janner Site, an isolated juvenile tibia of the cynodont Exaeretodon riograndensis (UFRGS-PV-1194-T) and a metatarsal of a semi-articulated and well preserved indeterminate dinosaur (UFRGS-PV-1099-T), present similar notches, less than 7.7 mm wide. This dinosaur presents a concentration of other marks including an ovoid pit mark (3 mm wide) on a vertebral centrum. The majority of the ichnofossils, however, occur on the distal epiphyses of the right femur: two trails of arcuate grooves, less than 1 mm long, which resemble the general shape of Osteocallis mandibulus Roberts et al. (2007); two 4-6 mm wide furrows surrounding the articular region, one of them ending in a circular perforation (5.9 mm wide) that penetrates the medullary portion of the bone; other perforation (5 mm wide) that only penetrates the cortical tissue. These perforations are round and conical in shape. An indeterminate fragmentary archosaur (MMACR-PV-012-T) from the Riograndia AZ (Late Triassic) presents three round perforations of at least 4.3 mm wide and two of more than 5 mm deep. Some recovered trace fossils are not compatible with dermestid patterns. One of them occurs on an articulated mandible of an adult E. riograndensis (UFRGS-PV-1177-T), from the Hyperodapedon AZ, which shows two irregular furrows formed by deep scratches. Other observed on the previously referred tibia of E. riograndensis (UFRGS-PV T) consists of small punctuations (less than 1 mm wide) arranged in a rosette pattern. These trace fossils resemble termite activity but these assignments are not well supported. Other trace fossils observed on a skull of Dindontosaurus (UFRGS-PV-0230T), from the Dinodontosaurus AZ, may represent insect perforations, furrows and bone damage, but the preservation of this material hampers further investigation. The other trace fossils here presented could represent ancient dermestid osteophagic behavior (Fodinichnia) or insipient pupal chambers (Cubichnia) corroborating an early Mesozoic origin to this group. 53

54 SLIC2013 Second Latin American Symposium on Ichnology A new occurrence of archosaur tooth marks on Late Triassic bones from southernmost Brazil Paes Neto, V.D., Pretto, F.A., Quezado de Figueiredo, A.E., Soares, M.B. and Schultz, C.L. Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil, [email protected] The recognition of tooth marks is not uncommon in the vertebrate fossil record, ranging from the end of the Paleozoic to the present, but few are described from the Triassic. Most of these trace fossils were produced on dicynodont bones from Middle to Late Triassic, as the proposed ichnotaxon Mandaodonites coxi Cruickshank (1986) that represents a bite mark probably produced by a rauisuchid, from the Middle Triassic of the Manda Formation (Tanzania). Trace fossils on a tibia of an indeterminate dicynodont collected in the Wozniki Limestone of Zawiercie (southern Poland) are interpreted as evidence of archosaur scavenging. From the Brazilian Riograndia Assemblage Zone (Santa Maria 2 Sequence, Paraná Basin), at least two specimens bear tooth marks. The sauropodomorph dinosaur Unaysaurus tolentinoi possesses small scratches interpreted as the activity of small cynodonts. The second source of data comes from archosaur tooth marks upon ribs and one left scapula of different specimens of the dicynodont Jachaleria candelariensis, the last element particularly matching with isolated archosaur teeth found on the same strata. We report another specimen (MMACR-PV-012-T), from the same Assemblage Zone, which consists on several bone fragments (more than 140) of an undetermined archosaur with varying dimensions. As much as 24% of them are at least 6 cm long and have a hollow medullary portion filled with sedimentary matrix. Two of these fragments present bisected perforations that trespass the cortical layer of the bone. One fragment contains a well-defined perforation (9.9 mm long and 5.2 mm wide) with radiating fractures on the surrounding edges. Following this mark, in an arcuate alignment, two other bisected traces are observed on the border of the fragment. The other fragment presents a bisected perforation (7.65 mm long and 5.5 mm wide), similar in shape to the other mark, but associated with a lateral fracture only. In the opposite view, a series of U-shaped scratches and small perforations are observed. The scratches are generally straight with some deviation, ranging from mm long and mm wide. One scratch is aligned with the perforation in the opposite side of the bone, and begins with a small perforation (4.4 mm wide), extending to 5.4 mm long and 1.6 wide. These trace fossils are different from insect traces found on other associated fragments, and the bisected perforations, scratches and the fragmentation are compatible with tooth marks. The bisected perforations are similar to trace fossils on the supracited scapula of J. candelariensis, with the same length, but a little wider. The depth of the marks could not be measured in the new specimen. These perforations are different from M. coxi in size and distances between teeth. The small perforation followed by the scratch mark is very similar to some traces described on the Polish dicynodont. These features allow us to infer that the trace fossils on this new specimen represent archosaur tooth marks, given the similarity with other trace fossils associated with this group. An isolated archosaur tooth was also found together with the fragments and its width and length are consistent with the perforations. This extends the record of these tooth marks to the end of the Triassic, evincing the feeding behavior of archosaurs at that time. Finally, we suggest that a specific nomenclature is needed to accommodate this group of trace fossils. 54

55 Abstracts and Intra-symposium Fieldtrip The Nereites Ichnofacies in the lower Paleozoic Río Seco de los Castaños Formation, Mendoza, Argentina: age, facies and trace-fossil content Pazos, P.J. 1, Heredia, A. 1 and Cingolani, C. 2 1 Instituto de Estudios Andinos don Pablo Groeber (IDEAN), CONICET-UBA. Dpto. de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Ciudad Autónoma de Buenos Aires, Argentina, [email protected] 2 Centro de Investigaciones Geológicas (CIG), CONICET-UNLP, La Plata, Argentina. The aim of this communication is to analyze different aspects related to an abundant ichnofauna recorded in the Río Seco de los Castaños Formation in the Bloque de San Rafael, Mendoza Province, Argentina. These aspects include: i) the discussion of the age of the unit from both biostratigraphic and absolute dating methods; ii) the analysis of the facies scheme previously suggested for the unit; iii) the documentation of the trace-fossil content; and iv) the analysis of the impact of the reconsideration of the age of the unit in ichnostratigraphic schemes. The units that traditionally were denominated the Lower Paleozoic flysch facies of the central western Argentina were intensely folded, faulted and low-grade metamorphosed during the latest (?) Devonian Chanic Orogeny. These are are well distinguishable in the field from the non-metamorphosed Pennsylvanian units. However, it is always a reason of controversy to assign some of them, in certain areas, to the Silurian or to the Devonian. In our case, the unit has been assigned to the Upper Silurian-lowest Devonian, based on palynomorphs and plant remains (primitive Lycophyta). In addition, the unit is intruded by rocks of Lower Devonian age, indicating the minimum possible age for the unit. The paleontological evidence is controversial: while palynomorphs suggest an Upper Silurian age, plant remains and a solitary coral remain point to a Devonian one. An Upper Silurian age is the most plausible; because the Devonian remains deserve further study. The flysch units were traditionally interpreted as deep-water turbidites, particularly the Devonian units, but later, a muddy platform-deltaic system developed in a foreland basin was suggested. The studied formation was interpreted as a deltaic system deepening from the east to the west. In this facies scheme the studied area is located to the west, where the Nereites-Mermia Ichnofacies was previously suggested, contrasting with the Cruziana Ichnofacies in the eastern outcrops. Organic matter (coaly levels) with plant remains decreases form the east (Atuel Cañon) to the west (N 144 road), but also turbidite-like deposits decrease in thickness and grain-size. The ichnofauna documented in the N 144 road locality contains dominantly Nereites irregularis Schafhäutl, Helminthopsis isp. and less abundant arthropod trackways and grazing traces. Microbial mats are very abundant but clearly not related to Nereites. At the Atuel Cañon locality, Nereites is also the most abundant ichnofossil but it contains more than one ichnospecies: Nereites irregularis and one beautifully preserved specimen of Nereites cambrensis Murchinson, the type ichnospecies of the ichnogenus. Other specimens could be assignable to the questionable Nereites delpeyi Borrouilh, a dubious ichnospecies that probably is a junior synonym of Nereites missouriensis Weller. Other well preserved trace fossil is Dictyodora in epirelief expressions. This ichnogenus contains several ichnospecies, with an apparently ichnostratigraphic value. The most abundant ichnospecies here are Dictyodora scotica Mc Coy, Dictyodora isp. and Dictyodora?tenuis Mc Coy; only one specimen of cf. Taenidium isp. was observed. Microbial mats are also abundant in levels containing Dictyodora, and the co-occurrence of Nereites and Dictyodora is not very common. Dictyodora is less abundant than Nereites. The abundance of organic matter, plants remains, coaly levels and microbial mats are in agreement with a relatively shallow depositional setting in a prograding deltaic system. This ichnofauna is very important because of the uncommon record, for the Upper Silurian of South America, containing the classical components of the Nereites Ichnofacies for the Palezoic, particularly in those records not attributed to basinal depositional settings. 55

56 SLIC2013 Second Latin American Symposium on Ichnology Zoophycos in fluvial facies of the El Imperial Formation (Pennsylvanian-Cisuralian) of the San Rafael Basin: the record of an overlooked transgression Pazos, P.J. 1, Rusconi, F. 1 and Gutiérrez, C. 2 1 Instituto de Estudios Andinos don Pablo Groeber (IDEAN), CONICET-UBA. Dpto. de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Ciudad Autónoma de Buenos Aires, Argentina, [email protected] 2 Dpto. de Ciencias Geológicas, Facultad de Ciencias Exactas y Naturales, Ciudad Autónoma de Buenos Aires, Argentina The Imperial Formation is one of the classical units of the late Paleozoic foreland basins in central-western Argentina. This basin has the particular feature that it is an engulfment openly connected with the paleo-pacific openly to the west, and consensus exists that fully marine facies are developed to the western part of the basin. The El Imperial Formation records stage II of the late Paleozoic glaciation toward the base and middle part and continue with postglacial transgressive black shales (stratigraphic marker), deltaic systems and fluvial facies, accordingly with the historical interpretation for the unit at the Atuel Cañon. However, a detailed examination of some levels that contain one of the few, if not the first, record of Zoophycos for the Late Paleozoic of Argentina, which documents a marine transgression that also, contains marine invertebrates (bivalves?) under study. The record of a marine interval in this part of the basin is relevant for stratigraphic correlations of the Carboniferous-Permian transition. Other levels contain the association of ichnogenera Diplocraterion and Psammichnites. The record of Zoophycos is very interesting because it combines features rarely observed in other Paleozoic records, such as the upward shafts, and also the morphologies observed in the lobes permit to differentiate several morphotypes: i) individual coils with alternating dark and light laminae, with small size and bulb external shape; ii) multi-coiled with very well preserved upper shaft; iii) forms with less vertical development and short but robust lobes. Interestingly, the up to 25 cm long upper shaft is a dark-walled, simple tube, and locally exhibits lateral displacement. Several specimens observed in cross section permit to compare morphological variations and in some cases Zoophycos is stacked in coarse-grained sandstones, something common in Spirophyton-like recordings in the literature, suggesting several episodes of sedimentation, colonization and erosion during times of short- term sea level changes or increasing subsidence. Sedimentary features observed in some beds of the analyzed interval include wave and tidal features, while heterolithic deposits containing black shales are surprisingly not related to Zoophycos, which is dominantly recorded in sandstone beds. The depositional setting for the studied interval is shallow marine, locally marginal marine with abundant organic detritus supply. Zoophycos has been reported from the Devonian of Brasil and Bolivia, and is here documented for the first time in Carboniferous deposits of Argentina. This ichnogenus indicates a normal marine environment where previously fluvial facies were suggested. In the same way, Psammichnites is stratigraphically younger that the known records from the Hoyada Verde Formation. The marine ichnofauna is related to an interval where petrographical changes are documented and is coeval with the eastern advance of the deformation front related to the San Rafael tectonic phase, at least in its first pulse, which is later recorded with a regional unconformity and the posterior complete continentalization of the basin with alluvial fan, aeolian and abundant ignimbrites deposits of the Choiyoi Group, well into the Cisuralian. 56

57 Abstracts and Intra-symposium Fieldtrip Cretaceous burrows of probable vertebrate origin from volcaniclastic interdune deposits of the Cerro Barcino Formation, Patagonia, Argentina Perez, M. 1, Umazano, A.M. 1, 2 and Melchor, R.N. 1, 2 1 INCITAP (CONICET - UNLPam), Santa Rosa, La Pampa, Argentina, [email protected] 2 Facultad de Ciencias Exactas y Naturales, UNLPam, Santa Rosa, La Pampa, Argentina The Albian alluvial-eolian Puesto La Paloma Member constitutes the basal unit of the Cretaceous Cerro Barcino Formation (Chubut Group in the Somuncurá-Cañadón Asfalto basin); which is mainly composed of sheet-like tuffaceous strata. For this contribution we measured one partial section (4.25 m thick) at Cerro Los Chivos ( ,72 S ,72 W), near Paso de Indios, Chubut province. This section is approximately 7.5 m above the limit with the underlying Los Adobes Formation. We recognized three types of tuffaceous deposits including sheet-flood, low relief eolian bedform and pyroclastic ash fall. All deposits represent interdune zones, which are covered and laterally replaced by eolian dune facies. Sheet-flood deposits are composed of finegrained tuffaceous sandstones with plane parallel lamination and without ichnofossils. Low relief eolian bedform deposits are constituted by fine-grained tuffaceous sandstones with low angle-cross bedding and lacking trace fossils. Pyroclastic ash fall deposits are composed of fine-grained tuffs with both rounded accretionary lapilli and ferruginous nodules. Trace fossil content is represented by root traces up to 10 cm long, Skolithos isp., Taenidium barretti and, in the top of the uppermost bed, we found silicified and mostly sub-horizontal large burrows, which are the subject of this contribution. The burrows are found in a well developed and intensely bioturbated paleosol. Studied material includes twelve collected specimens and several measured at the field. The best preserved specimens display an upper portion (ramp) with a maximum inclination of 20, and then the burrows become subhorizontal. In plain view, several burrow casts display a curved path composed of two segments forming an obtuse angle (about 115 ), with a rounded termination and no significant enlargement. The burrow casts, with a maximum length of 300 mm, have a flattened cross section, with a bilobed floor and a convex roof. A single specimen (probably a ramp) displays a cylindrical cross section. Average width is 61 mm (range: mm) and average height is 26 mm (range: mm). Burrow casts display a distinct surface texture in the form of groups of two or three parallel rounded ridges. Individual ridges are 1.9 to 2.5 mm wide and up to 31 mm long. The width of the pair of ridges is in the range mm and that of three parallel ridges is mm. The ridges are clearer in the roof of the burrow where it forms a curved path, criss-crossing in the center and then changing outwardly to subparallel to burrow walls. In the floor of the burrow casts, the ridges have a chevron-like appearance or are sub-parallel to the burrow axis. Considering the size, these burrows could be constructed both by vertebrates and invertebrates. The known examples of moderately large burrows with a prominent surface texture in the form of well-defined ridges or grooves are commonly attributed to tetrapods or decapod crustaceans. One additional feature of these burrow casts is the presence of a bilobed floor, which has been only reported in fossil and modern vertebrate burrows. The burrow cross-section suggests a producer with a dorso-ventrally flattened body. A bilobed burrow floor and massive fill is compatible with an open burrow system that is used repeatedly. The small size of these burrows excludes most of the vertebrate remains recovered from the Cerro Barcino Formation, which include titanosauriform sauropods, theropod dinosaurs, crocodyliforms, turtles and lepidosauromorphs. The most likely producers are lepidosauromorphs, although anurans cannot be discarded. The latter have a flattened body and burrowing habits, but are not recorded in the formation and commonly lack strong claws that may produce the observed scratch marks. 57

58 SLIC2013 Second Latin American Symposium on Ichnology Early Cretaceous ichnofauna from eolian and associated deposits of Patagonia: the Cerro Barcino Formation, Chubut, Argentina Perez, M. 1, Umazano, A.M. 1, 2 and Melchor, R.N. 1, 2 1 INCITAP (CONICET - UNLPam), Santa Rosa, La Pampa, Argentina, [email protected] 2 Facultad de Ciencias Exactas y Naturales, UNLPam, Santa Rosa, La Pampa, Argentina Trace fossil findings in Early Cretaceous eolian deposits are scarce. The Albian, alluvialeolian Puesto La Paloma Member is the basal section of the Cretaceous Cerro Barcino Formation (Chubut Group in the Somuncurá-Cañadón Asfalto basin). This unit offers a good opportunity to study organism-sediment interaction in Early Cretaceous eolian dunes and associated fluvial and lacustrine environments. For this contribution we measured four partial sections of the unit in three localities near Paso de Indios in the Chubut province. They are, from north to south, Cerro Los Chivos (18 m thick, ,78 S ,18 W), Huanimán (12 and 4 m thick, ,44 S ,88 W) and Estancia La Payanca (18 m thick, ,5 S W). Logged sedimentologic sections included trace-fossil bearing eolian deposits and associated fluvial, primary pyroclastic and lacustrine facies. Five types of deposits have been recognized including those of eolian dunes, pyroclastic ash falls, sheet-floods, shallow lakes and low-relief eolian bedforms. The last four deposits belong to interdune zone. Eolian dunes deposits are composed of fine-grained tuffaceous sandstones with tabular planar-cross bedding and subordinated trough, tabular tangential and low angle-cross bedding. The lack of grain-size contrast in eolian dune deposits makes recognition of trace fossils difficult. Skolithos isp. and root traces were found associated to second order surfaces (reflecting dune migration). Eolian dunes also contained, Taenidium barretti and Paleophycus tubularis developed parallel to foreset laminae, plus small mammal-like footprints, one tridactyl footprint and arthropod trackways. Mammal-like footprints are 27 mm long and 24 mm wide, have a triangular sole and three? short digit imprints with claw marks. Its morphology is roughly comparable with Brasilichnium. The tridactyl track is 29 mm long and 31 mm wide and the total divarication is 28º. Arthropod trackways are poorly preserved biserial rows of rounded imprints (about 3 mm wide) with series of 4 or 5 imprints. Low relief eolian bedform deposits are mainly composed of fine-grained tuffaceous sandstones with low angle-cross bedding and traslatent lamination, and subordinated massive tuffaceous sandstones. Trace fossil content is scarce and is represented by Skolithos isp., Taenidium barretti and rhizoliths. Sheet-flood deposits are occasionally associated with ash fall deposits showing accretionary lapilli. The former are composed of massive and laminated tuffaceous mudstones and fine-grained tuffaceous sandstones. Both deposits may overlie or underlie eolian dunes and display pedogenic features. One of the best developed paleosols (Cerro Los Chivos) contained a diffuse boxwork ichnofabric in the upper horizon, and a lower horizon with Edaphichnium lumbricatum, Taenidium barretti, Beaconites isp. and Skolithos isp. as discrete trace fossils. Another well developed paleosol (Estancia La Payanca) developed in tuffaceous mudstones and showing sphaerosiderite nodules and angular blocky peds, contained rhizoliths up to 10 cm long, Beaconites isp., Taenidium barretti and Skolithos isp. Finally, shallow lacustrine deposits covered by eolian dunes (Huanimán) are composed of massive and laminated tuffaceous mudstone levels with root traces, Taenidium barretti and Archaeonassa fossulata. The ichnofauna found in eolian dunes is similar to those reported from other roughly coetaneous eolian units from Brazil, namely the Guará and Botucatú formations (Upper Jurassic-Lower Cretaceous, Paraná basin). Elements shared by these units include mammal-like and tridactyl tracks, arthropod trackways and meniscate burrows. 58

59 Abstracts and Intra-symposium Fieldtrip Estudio icnológico de los clastos de una playa rocosa del Mioceno, Formación Concepción, Veracruz, México Pineda-Salgado, G., Quiroz-Barroso, A.S. y Sour-Tovar F. Departamento de Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, México, [email protected] Si bien el estudio de trazas de bioerosión en el registro fósil tiene una gran importancia para establecer la ubicación de antiguas líneas de costa y conocer la evolución de las comunidades marinas de ambientes marginales, este tipo de trabajos son incipientes en México. Como un ejemplo de su importancia se describe e interpreta el registro icnológico asociado a los clastos del conglomerado que aflora en el flanco este del Eje Neovolcánico, a una altitud de 280 metros sobre el nivel del mar, en las cercanías del poblado de Plan del Río en el estado de Veracruz, centro-sur de México. El conglomerado corresponde a la parte superior de la Formación Concepción, depositada durante el Mioceno. El estudio paleontológico previo de los bivalvos y gasterópodos incluidos en la matriz arenosa, así como la presencia de ostras y briozoarios en la superficie de los clastos, permitió relacionar a este conglomerado con el registro de una antigua playa rocosa. En el presente trabajo se realizó el estudio de los registros de bioerosión en los clastos, determinándose seis icnogéneros y nueve icnoespecies que corresponden a la actividad de poliquetos y/o sipuncúlidos (Caulostrepsis taeniola, Maeandropolydora sulcans y Trypanites weisei), de equinodermos (Circolites isp.), de esponjas clionidas (Entobia cateniformis, E. geometrica y E. ovula) y de bivalvos litófagos (Gastrochaenolites cluniformis, G. lapidicus, G. torpedo). A pesar de que se trata del registro de un sustrato móvil, la extensión de la bioerosión en los clastos que conforman el conglomerado permite asociarlo a la Icnofacies de Entobia, característica de sustratos duros que presentan una bioerosión profunda. La abundancia y diversidad de los icnogéneros Gastrochaenolites y Entobia en las icnoasociaciones estudiadas indica un ambiente marino somero, con una tasa de sedimentación muy baja acompañada de episodios de desplazamiento o rodamiento de los clastos, proceso que se infiere por la redondez y la presencia de bioerosión en la mayor parte de la superficie de los mismos. Los resultados del trabajo permiten comprender la historia genética del conglomerado, confirman su depósito en un paleoambiente de playa rocosa e indican la posición de la antigua línea de costa del margen occidental del Golfo de México durante el Mioceno. 59

60 SLIC2013 Second Latin American Symposium on Ichnology Inclusões de Dipnoi em coprolitos, Formação Rio do Rasto (Permiano Médio-Superior), Rio Grande do Sul, Brasil Quezado de Figueiredo, A.E. 1, Dentzien-Dias, P.C. 2 and Schultz, C.L. 1 1 Departamento de Paleontologia e Estratigrafia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brasil, [email protected] 2 Núcleo de Oceanografia Geológica, Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brasil Coprólitos que possuem restos ósseos entre suas inclusões são bem documentados na literatura. Porém, a presença de dentes é menos comum, especialmente placas dentárias de dipnoicos. Durante os trabalhos de campo realizados em 2008 e 2009 para o Membro Morro Pelado, Formação Rio do Rasto, nos municípios de São Gabriel e Aceguá, Rio Grande do Sul, diversos coprólitos foram encontrados. Todo material coletado foi descrito quanto à morfologia, mineralogia e inclusões. Dentre esses espécimes, quatro possuíam restos atribuídos a Dipnoi entre suas inclusões. UFRGS- PV-0397-P é um coprólito indeterminado, incompleto, sem estruturas, achatado, cujas dimensões são 16,5 por 15,4 mm, com altura de 7,8 mm. Possui inclusões de diversos fragmentos ósseos, uma escama ganóide de Paleonisciforme e restos de placas dentárias de Dipnoi indet., incluindo uma placa inteira com quatro cúspides, atribuída à família Ceratodontidae. UFRGS-PV-0427-P é anfipolar, com cinco voltas distribuídas por todo espécime. As dimensões deste coprólito são: comprimento total, 32,5 mm; largura maior, 20,3 mm; largura menor, 16,5 mm e altura de 12,2 mm. Internamente, contem escamas ganóides de Paleonisciformes, fragmentos ósseos e seis fragmentos de placas dentárias de Dipnoi indeterminado. O elemento melhor preservado é uma cúspide isolada de uma placa dentária afiada, cuja face lateral está voltada para o lado externo do coprólito. UFRGS-PV-0467-P é um coprólito fragmentado e não possui estruturas internas ou externas, envolto por uma camada de sedimento. Possui 20,2 mm de comprimento, 12,3 mm de largura e 7,8 mm de altura. As suas inclusões são escamas ganóides, fragmentos ósseos e uma placa dentária de dipnoico tetracuspidada (?), tentativamente identificada como de Gnathorhizidae. Também pertencente a esta família seria a placa dentária tricuspidada preservada em UFRGS-PV-0469-P. Este coprólito é arredondado, achatado e sem estrutura interna. Possui 20,3 mm de comprimento, 17,6 mm de largura e altura de 13,6 mm. Os coprólitos aqui descritos são morfologicamente distintos, podendo ser relacionado aos seus possíveis produtores ou aos distintos processos de fossilização. UFRGS-PV-0397-P; 0467-P e 0469-P não possuem estruturas internas e externas e não estão preservados completamente, sendo que apenas uma porção irregular de massa fecal está presente ao redor dos dentes. Os coprólitos arredondados e/ou sem estrutura parecem ter sido retrabalhados antes de seu soterramento final. A preservação da massa fecal ao redor dos dentes pode ter sido facilitada pela presença das cúspides e dentículos, que aumentaram a área de contato da mesma com a placa dentária. Desconsiderando a coprodiagênese, a inexistência de estruturas externas ou internas destes coprólitos pode ser associada, tentativamente, a fezes produzidas por alguns grupos de peixes sarcopterígios que não possuíam o intestino em espiral ou a anfíbios Temnospondyli. Já 0427-P é anfipolar e, ao contrário dos demais, foi soterrado mais rapidamente, e possivelmente um paleonisciforme ou um dipnóico podem ser relacionados como seus prováveis produtores. Porém, a perda de dados destes coprólitos dificulta fazer qualquer inferência mais específica sobre os possíveis produtores, além de indicar que os mesmos deveriam ser carnívoros ou detritívoros e se alimentavam no ambiente lacustre de água doce que caracteriza o Membro Morro Pelado da Formação Rio do Rasto. 60

61 Abstracts and Intra-symposium Fieldtrip The Zoophycos Ichnofacies in the Río Mayer Formation (Austral Basin, Patagonia): paleoenvironmental controls Richiano, S. Centro de Investigaciones Geológicas (CONICET-UNLP), La Plata, Buenos Aires, Argentina, The Río Mayer Formation (Berriasian-Albian) is part of the initial infill of the Austral Basin, southwestern Gondwana. At Los Glaciares National Park (Santa Cruz Province), specifically at the Seccional Río Guanaco, seven detailed sedimentary sections were measured. From a sedimentological point of view, this unit is mainly composed of black shales interbedded with marls and fine-grained sandstones. The combinations of these lithologies allow division of the unit into three major intervals. The lower interval (Berriasian-lower Valanginian) is almost exclusively composed of unbioturbated black shales. The middle interval is a 40 m thick succession of marls with thin intercalations of sandy levels. In this interval, the Zoophycos Ichnofacies (consisting of Zoophycos and Chondrites) was established during a moment of minimal sediment input from the continent during the Valanginianlower Hauterivian. Finally, the upper interval of the Río Mayer Formation (Hauterivian-Albian) consists of interbedded black shales and thin fine-grained sandstones. Only in the last few meters of this interval, trace fossils were recorded, as indicated by the association of the Zoophycos Ichnofacies and the Ophiomorpha rudis Ichnosubfacies. The sandy levels are related to the distal deltaic influence of the Piedra Clavada Formation during the Aptian-Albian. Overall, the Río Mayer Formation presents two different expressions of the Zoophycos Ichnofacies. First, in the middle interval, this ichnofacies is very well developed, with bioturbation index (BI) between 3 or 4. Zoophycos tunnels are nearly 1 cm wide and more than 1 m long. It occurs in a Transgresive Systems Tract associated with very low sedimentation rates. On the other hand, the ichnofacies in the upper interval is not well established, with BI between 0 to 1, and is associated with an Ophiomorpha rudis Ichnosubfacies. Zoophycos tunnels are shorter and 0.3 cm wide. These deposits record higher sedimentation rates due to deltaic progradation within a Highstand Systems Tract. The contrasting development of the Zoophycos Ichnofacies in the Río Mayer Formation was controlled by the paleoenvironmental stability reflected in the sedimentation rates. 61

62 SLIC2013 Second Latin American Symposium on Ichnology Characterization of bioerosion structures in marine Quaternary mollusks from Bahía Bustamante (Patagonia, Argentina): preliminary results Richiano, S. 1, 2, Aguirre, M.L. 2, 3, Davies, K. 3, Castellanos, I. 3 and Farinatti, E. 4 1 Centro de Investigaciones Geológicas, Conicet-UNLP, [email protected] 2 CONICET 3 Facultad de Ciencias Naturales, Universidad Nacional de La Plata 4 Universidad Nacional del Sur Bioerosion structures represent several kinds of activities (boring, drilling, rasping and scraping) by different organisms on hard substrates and can be the result of mechanical, chemical or a combination of both processes. The most common substrates able to be eroded in littoral environments are bioclastic remains. Mollusk assemblages are abundant and exceptionally well preserved in the marine Quaternary deposits along Argentina. The richest and thickest skeletal accumulations (mostly bivalve and gastropod shells) occur in beach ridges which reflect littoral palaeoenvironmental parameters during the most recent high sea-level stands. These deposits comprise parautochthonous assemblages accumulated during the last transgressive-regressive Mid-Late Pleistocene to Mid- Holocene marine cycles (Marine Isotope Stages, MIS 11 to 1). From a sedimentological point of view, the marine terraces from Patagonia have two different areas. First, the central area is mainly composed of massive, clast-supported conglomerate with scarce sandy matrix interpreted as the core terrace. On the other hand, above the massive core there are well-stratified sedimentary rocks (pebble conglomerates with abundant sandy matrix), representing the foreshore and shoreface deposits. These deposits commonly show low angle planar cross stratification and trough cross stratification. All the shells analyzed in this study came from the upper part of the terraces, where the shells are more abundant and better preserved. The bioerosion trace fossils present in these deposits comprise three ethological categories Domichnia, Fixichnia and Praedichnia. Macroborings (12 ichnotaxa) and microborings have been recognized. In order of abundance, the macroborings are: Oichnus, Iramena, Leptichnus, Maeandropolydora, Entobia, Caulostrepsis, Centrichnus, Renichnus, Pinaceocladichnus, Pennatichnus, Gastrochaenolites and Umbichnus. In Pleistocene deposits, Domichnia is the most common category, with 5 ichnogenera (Caulostrepsis, Entobia, Iramena, Maeandropolydora and Pinaceocladichnus) distributed in 53 mollusk specimens. In Holocene deposits, Praedichnia dominates, showing 75 shells with Oichnus. In the modern beach, Domichnia is again the most abundant category with 82 shells hosting 8 ichnogenera (Caulostrepsis, Entobia, Gastrochaenolites, Iramena, Maeandropolydora, Pennatichnus and Pinaceocladichnus). The deposits of Bahía Bustamante exhibit the greatest ichnodiversity recorded in marine Quaternary deposits of Patagonia up to present, including similar ichnotaxa to those identified along the Bonaerensian littoral. This preliminary study will bring light into several topics, such as interrelationships between different organisms, predation strategies and ethology. 62

63 Abstracts and Intra-symposium Fieldtrip Distribución de trazas fósiles en hemigrabenes: ejemplo en la formación Springhill, Cuenca Austral, Patagonia, Argentina Richiano, S., Varela, A.N. y Poiré, D.G. Centro de Investigaciones Geológicas (UNLP-CONICET), La Plata, Buenos Aires, Argentina, [email protected] La Formación Springhill fue definida en 1949, en el campo de explotación petrolera de Manantiales, Provincia de Magallanes, Chile. Esta unidad fue referida como un conjunto de rocas que se apoya sobre el Complejo el Quemado de manera disconforme, y que se compone de material derivado de éste. Se divide en dos partes, hacia el oeste del campo Manantiales presenta facies carbonosas (ambiente de lagoon), mientras que hacia el este es principalmente arenosa (ambiente de nearshore). El área de estudio se ubica en el Lago San Martín de la Provincia de Santa Cruz, Argentina. En dicha localidad, la Formación Springhill posee entre 50 y 100 m de espesor, y se encuentra rellenando un hemigraben del Complejo el Quemado. Se relevaron 4 perfiles sedimentológicos de detalle en esta unidad con una separación aproximada entre los perfiles extremos de 1,5 km. A partir de estas secciones se diferenciaron 3 paleoambientes de depositación para la Formación Springhill. La primera etapa se compone de depósitos fluviales, caracterizados por el desarrollo de canales y planicies de inundación con desarrollo de paleosuelos. Posteriormente, continúa una etapa transicional compuesta por depósitos de planicie de mareas. Finalmente, una transgresión marina genera la depositación de sedimentos litorales. Estos últimos depósitos son el foco principal de este trabajo dada importante participación de trazas fósiles en los sedimentos marinos de ambientes someros. Las cuatro secciones sedimentológicas se distribuyeron en posiciones diferentes del hemigraben, desde el borde hacia el centro. Es de destacar que si bien la posición dentro del hemigraben varía, los cambios sedimentológicos dentro de los niveles marinos someros son mínimos. En general este intervalo presenta areniscas desde medianas a muy gruesas con muy escasa participación de sedimentos finos. Las estructuras mecánicas más comunes son estratificación entrecruzada planar y en artesa, y la principal diferencia entre las cuatro secciones es el espesor del depósito, el cual varía desde 2,5 a 3 m cerca del borde del hemigraben hasta unos 5 m en la zona central. En el perfil ubicado en cercanías del borde del hemigraben se registraron los icnogéneros Skolithos, Arenicolites, Cylindrichnus, Ophiomorpha y Rosselia. Esta asociación representaría una expresión distal de la icnofacies de Skolithos, principalmente por la presencia del par Cylindrichnus-Rosselia. En el segundo perfil se registró principalmente Macaronichnus isp., con un diámetro cercano a 1 cm. En general, este tamaño de especímenes de Macaronichnus puede ser asignados tanto al upper shoreface como al lower shoreface. La orientación de esta traza fósil concuerda con una dirección perpendicular a la posible paleolínea de costa. En general, se encuentra acompañado por escasos ejemplares de Palaeophycus y Planolites. El tercer perfil presenta la mayor icnodiversidad, con los icnogéneros Arenicolites, Bergaueria, Diplocraterion, Ophiomorpha, Palaeophycus, Planolites, y Skolithos. Esta asociación constituiría una expresión proximal de la icnofacies de Cruziana. Finalmente, en una posición más interna del hemigraben sólo se registró Palaeophycus y Planolites. En conclusión, se observaron en la Formación Springhill variaciones en los contenidos icnológicos que habrían estado relacionados a la posición relativa dentro del hemigraben, pasando desde una icnofacies de Skolithos en cercanías del borde hasta una icnofacies de Cruziana en zonas más internas de la estructura. 63

64 SLIC2013 Second Latin American Symposium on Ichnology Trazas meniscadas en ejemplares de Uruguay rivasi de la Formación Asencio (Eoceno temprano) de Uruguay Roland, G. 1 y Verde, M. 1, 2 1 Departamento de Evolución de Cuencas, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay, [email protected] 2 ANII-SNI, PEDECIBA Geociencias. Uruguay, es un icnogénero correspondiente a la actividad de abejas, posiblemente Oxaeidos, que se encuentra en numerosos afloramientos de la Formación Asencio (Eoceno temprano) en varios departamentos de Uruguay y escasamente en la Formación Puerto Unzué de Entre Ríos en Argentina. El icnogénero incluye al momento dos icnoespecies válidas, U. auroranormae y U. rivasi. El bauplan básico consiste en celdillas de pared discreta con opérculo en espiral, antecámara y superficie interna lisa. Las mismas están agrupadas en filas (típicamente tres, aunque este número puede ser variable) de manera que los fondos de las celdillas divergen mientras que sus bocas convergen en un túnel principal longitudinal. Son comunes las perforaciones o depresiones ubicadas en la cara externa de sus celdillas. Estas han sido nominadas como Tombownichnus plenus y T. parabolicus. T. plenus fue definida por sus autores como perforaciones de sección transversal circular a sub-circular que atraviesan por completo una pared construida. A su vez T. parabolicus incluye depresiones parabólicas, cónicas o subcilíndricas en la cara externa de una pared construida. Durante la revisión de materiales pertenecientes a Uruguay presentes en la Colección de Paleontología de la Facultad de Ciencias (UdelaR) se seccionaron materiales de U. rivasi que en su interior contenían galerías de sección circular a sub-circular con relleno activo meniscado, de diámetro variable (10 a 15 mm). En un ejemplar, a juzgar por la orientación de los meniscos, la traza parece atravesar el nido por completo desde la base de las celdillas hacia la cara apertural, por lo que cabría una explicación ajena a la depredación y/o el cleptoparasitismo, por ejemplo, desplazamiento. Sin embargo, en otros ejemplares la traza está contenida en el nido y sigue la curvatura de los límites del clúster. Esto podría sugerir un comportamiento alimentario por parte del productor de la traza meniscada, buscando las provisiones y/o las larvas contenidas en las celdillas. La porción del clúster que contiene estas trazas meniscadas está completamente bioturbada, por lo que no se pueden distinguir las celdillas afectadas por la traza. Las nuevas trazas fósiles en U. rivasi, estarían evidenciando una relación de depredación/cleptoparasitismo sobre las larvas y/o provisiones de las celdillas por parte de un productor indeterminado. Estos materiales podrían justificar la creación de un nuevo icnotaxón aumentando la icnodiversidad de la Fm. Asencio. Este trabajo es parte de la tesis de grado de G.R. y ha sido financiado por el proyecto FCE 2007/44 de M.V. 64

65 Abstracts and Intra-symposium Fieldtrip Una nueva icnoespecie de nido de abejas del icnogénero Uruguay para la Formación Asencio (Eoceno temprano) de Uruguay Roland, G. 1 y Verde, M. 1, 2 1 Departamento de Evolución de Cuencas, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay, [email protected] 2 ANII-SNI, PEDECIBA Geociencias. El icnogénero Uruguay Roselli 1939 incluyó originalmente dos icnoespecies: Uruguay auroranormae y Uruguay castellanosi, descritas en base a materiales colectados en estratos de la Formación Asencio (Eoceno temprano), aflorantes en las cercanías del Arroyo Las Flores, en el departamento de Colonia. En 1987 Roselli describió Uruguay rivasi, diferenciando a esta traza de Uruguay auroranormae por poseer tres hileras longitudinales y por no distinguirse los fondos de las celdillas de manera individual en la base del nido, a la vez que creó el icnogénero Palmiraichnus para incluir la icnoespecie castellanosi. En el marco de una revisión morfológica de los ejemplares del icnogénero Uruguay de la Fm Asencio presentes en la Colección de Paleontología de la Facultad de Ciencias (UdelaR) se encontraron materiales que no se ajustan a las diagnosis existentes. En base a la morfología externa se pudo agrupar a los ejemplares en: Uruguay auroranormae, Uruguay rivasi, Uruguay n. isp. y Rosellichnus isp. En conjunto, estos ejemplares comparten un bauplan arquitectural similar. Las cuatro formas consisten en clusters de celdillas de pared discreta, opérculo en espiral, superficie interna lisa y antecámara. Por su parte, Uruguay n. isp. consiste en un cluster de celdillas de pared discreta, opérculo en espiral, superficie interna lisa y antecámara. Sin embargo, y a diferencia del resto de las mencionadas icnoespecies, en Uruguay n. isp. no hay un arreglo de las celdillas en filas y/o columnas. Más aún, tanto los fondos de las celdillas como sus bocas terminan en distintos niveles, por lo que no se pueden ubicar en un plano (e.g. Rosellichnus isp.) ni en una superficie curva (e.g. U. auroranormae y U. rivasi). Su contorno es difícilmente diagramable, raramente se definen filas y no parece haber dominancia de algún eje sobre otro. Sus celdillas son elongadas como en ejemplares de Rosellichnus, pero a diferencia de éste último, las mismas son recurvadas y se disponen de forma caótica. Se contabilizó el número de celdillas en seis clusters completos. En cinco de ellos, el número de celdillas osciló entre 9 y 11, mientras que en un ejemplar se contabilizaron más de 20 celdillas. Estos materiales justificarían la creación de un icnotaxón aumentando así la icnodiversidad de la Fm. Asencio. Este trabajo es parte de la tesis de grado de G.R. y ha sido financiado por el proyecto FCE 2007/44 de M.V. 65

66 SLIC2013 Second Latin American Symposium on Ichnology New findings of invertebrate trace fossils in a Late Miocene loess-paleosol succession, Cerro Azul Formation, La Pampa, Argentina Sostillo, R. 1, Cardonatto, M.C. 2, Montalvo, C.I. 2, Visconti, G. 2 and Melchor, R.N. 1 1 INCITAP (CONICET and Facultad de Ciencias Exactas y Naturales), UNLPam, Santa Rosa, La Pampa, Argentina, [email protected] 2 Facultad de Ciencias Exactas y Naturales, UNLPam, Santa Rosa, La Pampa, Argentina The Cerro Azul Formation is a monotonous succession of reddish-brown massive siltstones and fine-grained sandstones interpreted as loess deposits with development of calcareous paleosols (mostly comparable with mollisols). Sedimentological and paleontological evidence suggest deposition under a semiarid temperate and seasonal climate with savanna-like vegetation. In this contribution new findings of invertebrate trace fossils belonging to eight localities of the unit in La Pampa province are described. These localities are distributed in an area with a maximum latitudinal range of 200 km and more than 300 km in the E-W direction. The new material can be assigned to Coprinisphaera, Rebuffoichnus, Celliforma, Rosellichnus and Taenidium. The description of the trace fossil assemblages is arranged according to the dominant ichnofossils. Coprinisphaera isp. is only reported for Salinas Grandes de Hidalgo (SG; 37º S, 63º W) and Telén (TE; 36º S, 65º W) localities. Coprinisphaera isp. is spherical or hemispherical trace fossil with constructed wall with an average diameter of 29 mm and occasional occurrence of an emergence hole. Specimens of Taenidium barretti with arcuate menisci are also recorded from SG. Previous records of ichnofossils from these localities include Attaichnus kuenzelii, Coprinisphaera isp., Celliforma isp., vertebrate burrows and invertebrate meniscate burrows. The material from the remaining localities is assigned to Rebuffoichnus, Celliforma and Rosellichnus. Specimens of Rebuffoichnus are recorded from Caleufú (C; 35º S, 64º W), Las Torrecitas (LT; 36º S, 67º W), Estancia La Malvina (LM; 36º S, 64º W), Punta de la Barda (PB; 37º S, 67º W), and Bajo Giuliani (BG; 36º S, 64º W). Rebuffoichnus cf. sciuttoi (LT and LM) is an ovoid structure (mean diameter 18 mm) with a slightly oval cross section, a broken end and a surface texture in the form of fine ridges or rounded mounds. R. cf. casamiquelai and Rebuffoichnus isp. (PB, C, BG) are mm in diameter empty chambers with a thick wall showing millimetre-sized holes and an internal smooth ovoid cavity. Celliforma germanica (C) is a small cell (17 mm long, 7 mm wide) with a marked neck. Celliforma isp. is recorded from El Guanaco (EG; 36º S, 64º W) and Road 14 (R14; 36º S, 64º W) and consist of isolated cell casts (11 mm wide) with a rounded end and the other broken. Rosellichnus isp. (from EG) is a cluster containing at least 5 and probably 7 cells (about 32 mm long and 10 mm wide) arranged in a single layer and three rows with the ends of cells reaching the same level and showing a very thin wall. In addition, recovered from EG, a 22 mm wide burrow fill with a pseudomeniscate structure and a surface texture consisting of small rounded mounds and millimetre root traces. The trace fossil association from SG and TE is compared with the Coprinisphaera ichnofacies, typical of paleosols associated with herbaceous communities. Although scarce, the dominant trace fossil in the remaining localities are Celliforma and Rebuffoichnus in calcareous paleosols. The later are compared with the Celliforma ichnofacies, which is indicative of a drier climate and lower vegetation coverage than those represented by the Coprinisphaera ichnofacies, particularly scrubs and woodlands. The occurrence of both trace fossil associations probably reflects geographic and/or stratigraphic differences between the analyzed localities. 66

67 Abstracts and Intra-symposium Fieldtrip Ichnology of the brackish water intervals of the Puesto El Moro Formation, Upper Cretaceous, Austral Basin, Argentina Varela, A.N., Richiano, S. and Poiré, D.G. Centro de Investigaciones Geológicas (UNLP-Conicet), La Plata, Argentina, The Puesto El Moro Formation (Upper Cretaceous) was originally considered as a continental succession overlying the Piedra Clavada Formation. This unit is exposed in the region of Lake San Martin, near the homonymous Outpost belonging to the Estancia La Lila. The Puesto El Moro Formation is coeval with the Mata Amarilla Formation; both formations are of great interest because they mark the onset of the foreland stage of the Austral Basin. A detailed sedimentological logging at the type locality allows the identification of three main intervals. The lower interval corresponds to a littoral paleoenvironment, and the middle and upper intervals were developed in continental (fluvial) paleoenvironment. The lower littoral interval is composed of an alternation of commonly bioturbated medium-grained sandstone, with greyish flaser-bedded heterolithic deposits, locally exhibiting trace fossils. The ichnofauna is dominated by Thalassinoides isp., accompanied by Ophiomorpha nodosa, Palaeophycus isp. and Sinusichnus sinuosus. This ichnoassociation corresponds to an impoverished Cruziana Ichnofacies developed in a marginal shallow marine palaeoenvironment with salinity stress and / or oxygen depletion. Most of these ichnotaxa are produced by callianassid crustaceans that used the galleries for different purposes, including dwelling (domichnia) and bacteria cultivation (agrichnia). Similar examples, which could be used as analogues for paleoenvironmental characterization, can be found in the Pliocene marginal marine deposits of France and Spain (the type locality of the ichnogenus Sinusichnus), in deltaic deposits of the Oligocene-Miocene of Venezuela, and in the Cretaceous of Antarctica. 67

68 SLIC2013 Second Latin American Symposium on Ichnology Insect trace fossils diversity in ultisols and calcisols, and paleoclimatic oscillations during the Late Cretaceous to Palaeogene in Uruguay Verde, M. SNI-ANII, PEDECIBA Geociencias, Paleontología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay, Insect trace fossil assemblages in paleosols are common in several lithostratigraphic units of Uruguay. The most common trace fossils are insect nests (Calichnia) and pupal chambers (Pupichnia). They occur in the Mercedes Fm. calcisols (late Cretaceous), the Asencio Fm. ultisols (early Eocene), and the Queguay Fm. calcisols (Eocene-Oligocene), which overlies the Asencio Fm. Multi celled bee nests like Uruguay ispp. are specially abundant in the Asencio Fm. together with Palmiraichnus, a kind of one celled bee nest. Monesichnus (unidentified trace maker) and Teisseirei (a lepidopteran pupal chamber) are also very common. Other pupal chambers belonging to coleopterans like Rebuffoichnus casamiquelai are abundant only in some outcrops. The bee nests Corimbatichnus and Elipsoideichnus, both endemic of the Asencio Fm., are relatively rare. Cellicalichnus isp. (another rare bee nest) is also present and documented with only one specimen in this unit. Celliforma s. str. has not been recorded unequivocally yet, but this situation may represent a bias in preservation. Dung beetle brood balls, Coprinisphaera, are not the most abundant ichnofossils in the Asencio Fm. The Coprinisphaera ichnospecies recorded are: C. murguiai (=C. ecuadoriensis), C. kraglievichi and C. kheprii. Other trace fossils like meniscated tubes are scarce and present only in a few outcrops. Termite nest (Krausichnidae indet., aff. Krausichnus) are also rare members of the Asencio Fm. ichnoassemblages. Some cleptoparasite traces (e.g. Tombownichnus and Lazaichnus) occur on nests and pupal chambers. The Asencio Fm. is a high diversity case of the Coprinisphaera Ichnofacies, which represents paleosols developed in ecosystems characterized by a variety of herbaceous communities. As originally defined, it ranges from warmer and more humid environments (tropical savannas) where termite nest may be present, to more temperate and arid environments (steppes) where hymenopteran nests are dominant. The Asencio Fm. shows virtually absence of termite nests (a few Krausichnidae indet.) and a relative dominance by bee nests. The limestone units are less ichnodiverse than the Asencio Fm., nevertheless, when compared to other units with calcareous paleosols around the world, these units equal or even surpass all of them in terms of insect trace fossil diversity. One celled bee nest is a dominant element of these ichnoassemblages (Celliforma germanica, C. rosellii and C. spirifer). Other bee nests like Caenohalictini nest not formally described, yet, are very scarce. Pupal chambers like Fictovichnus gobiensis are also dominant elements of these limestone units. A few specimens of C. murguiai were also found in one locality, which could represent a rare case of ichnofacies overlapping. Pallichnus isp. may be present also in these units with some degree of doubts. The Uruguayan limestone units, are emblematic cases of the Celliforma Ichnofacies. Compared to other calcareous paleosol assemblages around the world, the Uruguayan ichnoassemblages are highly diverse, specially the Queguay Fm. This ichnofacies represents paleoenvironments with poor vegetation coverage in terrestrial settings and bare soil when developed on palustrine carbonates under subhumid to sub-arid climates. The stratigraphic arrangement of the units treated here, their lithology and ichnoassemblages suggest arid to subarid conditions during the late Cretaceous, followed by tropical to subtropical more humid climate developed during the early Eocene. The Queguay Fm. records a return to the arid to subarid climate during the mid-late Eocene or even the Oligocene. This is a synthesys of the doctoral studies of M.V. DINACYT (FCE ), ANII (FCE ), PEDECIBA and CSIC co-funded this work. 68

69 Abstracts and Intra-symposium Fieldtrip Castrichnus n. isp., earthworm aestivation chambers in early Holocene paleosols from southern Uruguay Verde, M. 1, 2, Ubilla, M. 1 y Roland, G. 1 1 Paleontología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay 2 ANII-SNI, PEDECIBA Geociencias, [email protected] Despite their abundance and intense activity in recent soils, earthworms are rare as body fossils (doubtful fossils, cocoons and calcium carbonate aggregates) in the geological record, and only a few ichnotaxa coming from paleosols have been ascribed to these animals. Among them are Edaphichnium lumbricatum, a cylindrical tunnel filled with pellets; Castrichnus incolumis, a subspherical chamber with a wall constructed of flattened pellets and filling composed of pellets and menisci; and possibly Taenidium serpentinum a meniscate tunnel. The new trace fossil material reported herein comes from paleosols developed on flood plain unnamed silty facies. They were collected near to San Ramón Town, on the Pilatos Creek bank (Canelones County, southern Uruguay). These silty facies overlie sandy levels with /-965 (UIC-2823) and /-670 years (UIC- 3067) OSL ages (sandy samples); in turn, argilaceous-sandy facies underlying the second ones, were dated with 14 C /-140 years BP (AA91726) (deer tooth enamel). The silty facies yielded a diverse fossil mammal fauna including extinct horses, deer, camelids, and armadillos among others. Some of these mammals suggest open habitats as the horse Equus cf. E. neogeus and the large extinct camelid Hemiauchenia. Taphonomic features of the fossil mammalian assemblage preclude at first glance reworking processes from older beds (similar way of preservation, lack of abrasion, articulated and semiarticulated skeletal remains). Bones also share similar marks likely due to soil influence. The new trace fossils are subspherical to piriform chambers, having a cylindrical tunnel, straight to sinuous, attached to the upper hemisphere of the chamber, and vertical to subvertically oriented. Many of the chambers, and sometimes the vertical tunnels, are filled with cylindrical pellets with rounded ends. The wall is a simple lining, perhaps a result of the excavation of the chamber, by compression of the surrounding sediments and its cementation by secretions of the producer. Forty specimens were measured: equatorial diameter: mm, (n = 39; mean = 6.71 mm), height from base of chamber to tunnel mouth: mm, (n = 30; mean = 6.52 mm), and tunnel diameter: mm, (n = 26; mean = 0.95 mm). When compared with other known trace fossils from paleosols, a similarity with the bauplan of Castrichnus incolumis arises. C. incolumis is the only trace fossil formally described as an earthworm aestivation chamber until present. One significant morphological difference between these trace fossils is the absence of a discrete wall constructed with pellets as that of Castrichnus incolumis. This character represents a different behavior in chamber construction, which would separate the new materials in a new ichnospecies of Castrichnus. Another difference in the new materials is their tiny size, notoriously smaller than C. incolumis. Differences in behavior and size suggest that the constructors of C. incolumis and the new trace fossils were not the same earthworms. This work was partially funded by grant ANII-FCE to M.U. 69

70 SLIC2013 Second Latin American Symposium on Ichnology Análisis preliminar de rastro de iguanodonte (Dinosauria, Ornithopoda) en el Cretácico Temprano de Los Conchucos (Andes del norte peruano) Vildoso Morales, C.A. y Sciammaro, M.P. Instituto Peruano de Estudios en Paleovertebrados, Lima, Perú, [email protected] Desde el año 2001 se han producido notables hallazgos de icnitas de tetrápodos (principalmente dinosaurios) en la zona altoandina de los Conchucos (Región Ancash, Norte del Perú) en localidades ubicadas a alturas promedio de 4600 m.s.n.m. La mayor parte de estas localidades está comprendida dentro de la Formación Carhuaz (Hauteriviano-Barremiano), constituida por areniscas de grano medio a fino, calizas y carbones depositados en áreas costeras durante una etapa regresiva. Las capas de la Fm. Carhuaz evidencian efectos del intenso plegamiento local, presentando una marcada inclinación que puede llegar o incluso superar los 90. Una de las localidades más importantes es la denominada Kilómetro 80, situada a la altura del hito del mismo nombre en la carretera que conduce al campamento minero de Yanacancha (Compañía Minera Antamina), donde las obras de construcción de la misma expusieron una amplia superficie de posición prácticamente vertical, con alrededor de un centenar de huellas pertenecientes a dinosaurios. La mayor parte de las icnitas expuestas en esta localidad corresponden a Theropoda de diferentes tamaños, concentradas principalmente en la mitad N. de la superficie aflorante. Sin embargo, sobre la mitad S. de la misma se aprecia un rastro bien diferenciado y relativamente aislado, cuyos rasgos indican pertenencia a un dinosaurio Iguanodontidae. Este rastro consta de 10 huellas de un individuo de talla grande, a juzgar por las dimensiones de aquéllas donde se tiene un diámetro máximo anteroposterior (tomado desde el extremo proximal del dígito III hasta el punto de mayor curvatura del borde posterior de la pisada) de 644 mm. en promedio; el diámetro máximo mediolateral (tomado entre los dígitos II y IV) de las huellas es de de 562 mm. El recorrido del rastro es de m en la parte conservada o expuesta de la superficie con icnitas. La asignación a Iguanodontidae se basa en primer lugar en la morfología de las huellas. Las diferencia entre ancho y largo es muy escasa. Las impresiones de los dígitos no muestran presencia de garras, siendo éstos además de longitud sensiblemente similar. El borde posterior de las huellas no muestra indicio alguno de hallux, siendo por el contrario de contorno suavemente curvado. El ángulo de paso se ha tomado como otro argumento para reforzar la asignación a un iguanodóntido, al arrojar valores de lo que cae dentro del rango generalmente considerado diagnóstico para icnitas de iguanodontes. No se han identificado en el Km. 80 otras huellas atribuibles con seguridad a iguanodontes, con la sola excepción de un probable rastro en la mitad N., bastante mal conservado y que sigue la misma dirección del grueso de los de terópodos. Es remarcable en este yacimiento que, mientras la mayor parte de rastros de terópodos (incluyendo todos los de tamaños mediano a grande) presenta una dirección de marcha predominante NW, el del iguanodonte toma una dirección SE y luego SSW, notablemente divergente u opuesta a la seguida por los primeros, lo que puede deberse, entre otras causas probables, a conducta de evasión respecto de la ruta de tránsito de los depredadores. Esta presentación forma parte del Proyecto Dinosaurios de Antamina, apoyado por Compañía Minera Antamina. 70

71 Abstracts and Intra-symposium Fieldtrip Inferencias paleoambientales en torno a huellas de saurópodos (Dinosauria, Sauropodomorpha) en el Albiano de Yanashalla, Andes del norte peruano Vildoso Morales, C.A. y Sciammaro, M.P. Instituto Peruano de Estudios en Paleovertebrados, Lima, Perú, [email protected] La localidad de Yanashalla (Región Ancash, Norte Peruano), ubicada en las cadenas montañosas del extremo S. de la zona de los Conchucos, por encima de los 4800 m.s.n.m. presenta extensos afloramientos de calizas oscuras de origen transicional a marino somero, pertenecientes a la Formación Pariatambo, y depositadas durante una etapa transgresiva, cuya edad ha sido determinada como Albiana temprana en base a cefalópodos. Esta unidad estratigráfica ha librado notables materiales de vertebrados, que vienen siendo estudiados desde el año Los dos tercios superiores de la Fm. Pariatambo están dominados por lutitas con algunas areniscas finas y coquinas en niveles bien definidos; estos niveles contienen notables cantidades de restos de vertebrados e invertebrados marinos. El tercio inferior de la Fm. Pariatambo se caracteriza por la predominancia de lodolitas carbonáticas de color grisáceo a negruzco, y menos comúnmente areniscas finas de color pardo oscuro a gris parduzco, con ondulitas orientadas sobre el eje principal ESE-WNW. En los niveles de lodolitas se registran numerosas icnitas de dinosaurios saurópodos, asociadas a abundantes restos dispersos de vertebrados, invertebrados y vegetales, generalmente fragmentarios. Las icnitas están bastante bien marcadas, pero los bordes se ven bastante suavizados; la depresión que constituye la huella propiamente dicha está rodeada por un amplio reborde, poco elevado y de contorno exterior débilmente marcado; en estos rasgos se evidencia erosión posterior a la generación de la huella y endurecimiento del sedimento. Un detalle notorio es la presencia de fragmentos óseos o de restos vegetales en el interior de algunas huellas, lo que se interpreta como el resultado de desplazamiento de los saurópodos por encima de un sustrato con cierto grado de consolidación, y en el cual hubo acumulación previa de restos orgánicos, los que fueron aplastados por los animales en marcha. Estos rasgos, junto con la litología y las estructuras sedimentarias asociadas, se toman como indicadores de que las icnitas fueron producidas en ambientes costeros sujetos a la acción regular de las mareas. Tras generarse las huellas, éstas quedaron sometidas a la acción desecante de la atmósfera, consolidándose para luego experimentar la acción erosiva del agua, no por un lapso muy prolongado aunque suficiente para causar un leve desgaste en las huellas. La reconstrucción paleogeográfica tentativa de esta región durante el lapso de depositación de la Fm. Pariatambo postula la existencia de una costa baja, con islotes separados entre sí por canales de escasa profundidad que incluso pudieron estar secos durante los períodos de marea baja. Es factible pensar que las huellas de Yanashalla corresponden al tránsito de animales por el lecho de esos canales, posiblemente entre los islotes o entre estos y el continente. Los rasgos mostrados por estas icnitas y su contexto inmediato refuerzan la hipótesis arriba citada sobre los tipos de ambientes predominantes en esta parte de los Conchucos durante el Albiano temprano. Esta presentación forma parte del Proyecto Dinosaurios de Antamina, apoyado por Compañía Minera Antamina. 71

72 SLIC2013 Second Latin American Symposium on Ichnology Triassic deposits and ichnofossils of Transbaikalia (Russia) Vilmova, E.S. North-Eastern State University, Magadan, Russia, The Sredneononskiy basin (10х100 km 2 ), made of terrigenous deposits of the Aksha-Ilia series (4500 m thick), is located in the southeast of Transbaikalia. This complex basin is divided into several blocks. The Late Permian-Early Triassic age of the Aksha-Ilia series is based on conodonts and radiolarians. The consolidated section of the Aksha-Ilia series consists of three suites (from base to top): Aginskaya, Zutkuleiskaya and Tulutaiskaya. The Aginskaya suite (1800 m thick) consists of a cyclic sandstone-dominated succession. Late Permian-Early Triassic fossils include conodonts such as Gondolella prolonga (Wardlaw, Collison) and Neogondolella foliata (Bud.), and radiolarians such as Spongentactinella sp., Entactinosphaera sp. and Helioentactinia sp.; crinoidal fragments are rarely present in limestones. The trace fossil Phycosiphon incertum Fisher-Ooster occurs in siltstones. The Zutkuleiskaya suite (1800 m thick) consists of a cyclic intercalation of sandstones and siltstones. Lenses and interbeds of conglomerates and lava flows are rare. The siliceous tube-like forms Rozanites bengtsoni Sinitsa and R. brasieri Sinitsa were found in the siltstones. The trace fossils Phycosiphon incertum Fisher-Ooster, Nereites missouriensis (Weller) and Planolites isp. (Zutkuley association) are widespread in layers lacking Rozanites. The Tulutayskaya suite (800 m thick) is mostly represented by unfossiliferous sandstones with rare lenses of siltstones and conglomerates. The Zutkuley association is also found in the deposits of the Borzinskiy and Zun-Shiveya areas and in other Triassic sections of Transbaikalia. Late Permian Early Triassic bivalves [Kolymia cf. inoceramiformis Lich, Dacryomya cf. sakaradaniensis Ichik., Palaeonucula subaequilatara (Reed)], gastropods (Mourlonia sp.), brachiopods (Linoproductus sp., Rhynchopora sp.) and crinoids (Neocamptocrinus ex gr. rudicostatus Stuk.) are known in these deposits. The Triassic succession (1500 m thick) in the south of the Jewish Autonomous Region of the Khabarovsk territory, which has been studied in 2001, has the same cyclic pattern of pebble conglomerates followed by sandstones or siltstones. These deposits contain Early (Nordophiceras cf. schmidti Okuneva, Hellenites cf. inopinatus Kipar) and Middle (Stenopopanoceras cf. babstovense Okuneva, Leiophyllites praematurus Kipar) Triassic cephalopods, bivalves (Pseudoclaraia zakharovi Okuneva, P. cf. beltenevi Okuneva), and fragmentary crinoids and fishes. Trace fossils are less abundant than in the Zutkuley association. The comparison of Triassic deposits of these regions suggests that the successions in Transbaikalia and the Khabarovsk territory display similar pattern of cyclicity. The association of the deep-sea Zutkuley ichnofossils with the tube-like Rozanites is typical of the Transbaikalia successions. However, the shallow-water cephalopod, bivalve and crinoid fauna is restricted to the Khabarovsk territory. 72

73 Abstracts and Intra-symposium Fieldtrip Presencia de la Icnofacies de Glossifungites en la base de la Formación Santa Cruz (Mioceno inferior-medio), sudeste de la provincia de Santa Cruz, Patagonia Austral Zapata, L. 1, Krapovickas, V. 2, Raigemborn, M.S. 1, Matheos, S.D. 1 1 Centro de Investigaciones Geológicas, (CONICET - UNLP), La Plata, Argentina, [email protected] 2 IDEAN-CONICET, Departamento de Ciencias Geológicas, FCEyN, UBA, Buenos Aires, Argentina En el sector costero del sur de la provincia de Santa Cruz, afloran los depósitos marinos someros de la Formación Monte León (Mioceno inferior) y, mediante un pasaje transicional, los depósitos principalmente continentales de la Formación Santa Cruz (Mioceno inferior-medio). El objetivo de este trabajo es dar a conocer las trazas fósiles presentes en una superficie de discontinuidad ubicada en la base de la Formación Santa Cruz. La sucesión sedimentaria portadora de las trazas fósiles aquí analizadas aflora al norte de la desembocadura del río Coyle. La misma se compone de facies heterolíticas (intercalaciones de areniscas muy finas y pelitas masivas) (Het), tobas finas a medias retrabajadas con estratificación entrecruzada en artesa difusa a masivas, edafizadas y bioturbadas (Tm), y areniscas finas a gruesas bioturbadas, con estratificación entrecruzada en artesa (St), planar (Sp) y laminación ondulítica (Sr). En la localidad septentrional (Rincón del Buque Norte), las trazas fósiles presentes en las facies Tm corresponden a marcas de raíces delgadas (1-2 mm de diámetro) de coloración marrón claro, y otras mayores de 1-2 cm de diámetro, de coloración naranja amarillento oscuro. Adicionalmente, presenta galerías tridimensionales asignadas a Thalassinoides isp. Estas estructuras son atribuidas a la actividad de crustáceos decápodos y se caracterizan por la presencia de elementos verticales y horizontales, bifurcaciones en forma de T e Y, sección circular de 2-3 cm de diámetro, limites netos y rellenas pasivamente por el material suprayacente. Las facies St y Sp presentan estructuras tridimensionales aisladas asignadas a Ophiomorpha isp. junto con abundantes pellets fecales aislados de Ophiomorpha isp. En la localidad austral (Ea. Coy Inlet), las trazas fósiles presentes en las facies Tm corresponden a marcas de raíces delgadas con un diámetro variable entre 1 y 2 mm de coloración naranja amarillento oscuro. Así mismo se preservan estructuras de habitación o domicilio de bivalvos perforantes con forma general de botella o gota asignadas a Gastrochaenolites lapidicus. Las mismas presentan un diámetro basal entre 1 y 4 cm, un largo máximo de 10 cm, limites netos y se encuentran rellenas pasivamente por el material suprayacente. La facies St presenta pellets fecales aislados de Ophiomorpha isp. y trazas de habitación simples correspondientes a Palaeophycus tubularis. La asociación de trazas de decápodos constructores de galerías (Thalassinoides isp.) y bivalvos perforantes (Gastrochaenolites lapidicus) es interpretada como perteneciente a la icnofacies de Glossifungites. Esta icnofacies es característica de sustratos firmes y presenta una asociación de trazas fósiles desarrolladas bajo condiciones sustratocontroladas en ambientes marinos someros. Las trazas fósiles preservadas en las facies Tm, sugieren que estos niveles fueron depositados en un ambiente continental, donde la exposición subaérea dio lugar al desarrollo de rasgos edáficos, y posteriormente sobre éstos se instauró un ambiente marino somero, que permitió el desarrollo de la Icnofacies de Glossifungites, evidenciando una superficie de discontinuidad. Variaciones en las condiciones de la consolidación del sustrato habrían sido el principal factor de control para el desarrollo de una colonización diferente de la Icnofacies de Glossifungites en ambos sectores (Gastrochaenolites lapidicus en el sur y Thalassinoides isp. en el norte), dado que los bivalvos prefieren sustratos relativamente más firmes para su desarrollo en comparación a los crustáceos. Por su parte, la baja icnodiversidad y la dominancia de trazas fósiles verticales de niveles profundos de la icnofacies de Skolithos (Ophiomorpha isp. y pellets fecales de Ophimorpha isp.) en facies St y Sp, sugieren el origen marino de estos niveles desarrollados en condiciones de alta energía. De confirmarse el reconocimiento de esta superficie de discontinuidad portadora de la icnofacies de Glossifungites en otros sectores de la región, la misma podría llegar a ser clave para definir el pasaje transicional entre las Formaciones Monte León y Santa Cruz. 73

74 SLIC2013 Second Latin American Symposium on Ichnology 74

75 Abstracts and Intra-symposium Fieldtrip Intra-Symposium Fieldtrip Salinas Grandes de Hidalgo Macachín La Pampa, Argentina September 18,

76 SLIC2013 Second Latin American Symposium on Ichnology 76

77 Abstracts and Intra-symposium Fieldtrip LATE MIOCENE ANT NESTS AND ASSOCIATED ICHNOFOSSILS FROM PALEOSOL: THE CERRO AZUL FORMATION AT SALINAS GRANDES DE HIDALGO, LA PAMPA, ARGENTINA Ricardo N. Melchor 1,2, Graciela Visconti 2, and Claudia I. Montalvo 2 1 INCITAP (CONICET-UNLPam), Av. Uruguay 151, (6300) Santa Rosa, La Pampa, Argentina. 2 Universidad Nacional de La Pampa, Facultad de Ciencias Exactas y Naturales, Av. Uruguay 151, (6300) Santa Rosa, La Pampa, Argentina. Introduction During the fieldtrip we will visit Salinas Grandes de Hidalgo, a classic locality for Miocene fossil vertebrates of Argentina. The locality is also significative for paleosol ichnology because this was the place where Laza (1982) described the first fossil ant nest, Attaichnus kuenzelii. The trace fossil bearing outcrops were referred as belonging to the Epecuén Formation by Laza (1982) following Pascual et al. (1965), however, they are now considered as part of the Cerro Azul Formation (Goin et al., 2000). The ants proposed as producers belong to the fungus-growing tribe Attini and some relevant paleoenvironmental and paleocological inferences were made on the basis of the finding (see also Genise et al., 2013). These fossil ant nests are very abundant in outcrop today and we will revise this trace fossil in addition to other ichnofossils from paleosols. Besides the paleontological and ichnological meaning of the locality, the saline lake is commercially exploited to produce sodium chloride essentially in the form of table salt. After harvesting the salt is accumulated in mounds near the saline lake before further processing. The Cerro Azul Formation The Cerro Azul Formation comprises late Miocene continental sedimentary rocks (sandy silt and silty sand) that appear in discontinuous outcrops in most of La Pampa province (Fig. 1). The maximum exposed thickness in outcrop is 54 m, although the unit reaches about 180 m in the subsurface (Visconti et al., 2010). This formation is mainly composed of siltstones and sandstones arranged in monotonous strata (92% of succession), with mudstones intercalations in the bottom (7%). The top of the unit commonly contains a calcrete. Siltstones are clayey and carbonate cemented, poorly sorted, and usually light brown (5YR 6/4) to reddish pale brown color (10R 5/4). Silty sandstones have moderate selection, pale pink orange color (5YR 7/2), clay matrix and carbonate cement. These are classified as lithic wackes or feldspathic lithoarenites. A friable appearance and fine and uniform grain size of materials are common features for the succession. At Salinas Grandes de Hidalgo, the outcrops of the Cerro Azul Formation fringes a large saline depression, located about 13 km southeast of Macachín city, southeast La Pampa province (Fig. 2). 77

78 SLIC2013 Second Latin American Symposium on Ichnology Fig. 1. Distribution of the outcrops of the Cerro Azul Formation. Sedimentary paleoenvironment Preliminary sedimentological interpretations (Visconti et al., 1996; Goin et al., 2000) allowed distinguishing well-developed eolian deposits with numerous paleosols (Melchor et 78

79 Abstracts and Intra-symposium Fieldtrip al., 2000; Visconti, 2007) and scarce lacustrine and fluvial deposits (Visconti and Montalvo, 1990; Goin et al., 2000). The unit is mainly composed of silty deposits of eolian origin with intercalated paleosols. These deposits have been interpreted as loessites (Pye, 1987) from their lithological and outcrop features. These include dominant silt-sized sediments, friable consistency, massive beds, tabular external geometry, mantiform areal distribution and lack of erosive basal contacts (Spalletti, 1992). Distinctive paleosols would represent wetter climatic conditions developed on sediments of eolian origin (Tsoar and Pye, 1987), deposited in distal areas of the sedimentary basin. Fossil mammals found in this formation (Goin et al., 2000) are typical of open environments, similar to savannas. Fig. 2. Google Earth image of the Salinas Grandes de Hidalgo with the stops to be visited. Age and paleontological content The unit has abundant vertebrate fossils that mostly belong to the Huayquerian South American Land Mammal Age (Montalvo and Casadío, 1988, Verzi et al., 2008), whereas the vertebrate faunal association of some localities suggest comparison with the older late Miocene Chasicoan Land Mammal Age (Verzi, 1999, Verzi et al., 2008). The faunal record is fairly diverse although the major component are mammals of the orders Didelphimorphia, Sparassodonta, Paucituberculata, Argyrolagida, Xenarthra, Notoungulata, Litopterna, Rodentia and Carnivora (Fig. 3) (e.g., Goin et al., 2000, Urrutia et al., 2008, Cerdeño and Montalvo, 2001, 2002, Verzi et al., 2008). Remains of aves, amphibians and reptiles were also recorded (Albino et al., 2006, Albino and Montalvo, 2006, Cenizo et al., 2012). 79

80 SLIC2013 Second Latin American Symposium on Ichnology Fig. 3. Representative silhouettes of major fossil mammal groups from the Cerro Azul Formation. Avian remains are scarce (Campbell and Tonni, 1980), although some of the salient findings are those of phorusrhacos, large predatory birds (Vezzosi, 2012; Cenizo et al., 2012). The Phorusrhacidae are a family of large to gigantic extinct birds, endemic of South America that played the ecological role of carnivores. The scarcity of large carnivorous mammals during the Cenozoic favored the development of phorusrhacos that occupied that role in different communities. This locality has yielded few but interesting remains of the giant teratorn Argentavis magnificens (Teratornithidae), the World largest flying bird. A. magnificens was a scavenger with a wingspan of about 7 m and 80 kg of body mass (Fig. 4). It is inferred that A. magnificens flew mainly by soaring, using flapping flight only during short periods (much like the extant Andean condor and vultures). It is probable that it used thermal currents as well (Chatterjee et al., 2007). Fig. 4. Reconstruction of Argentavis magnificens in comparison with humans and an airplane (modified from Chatterjee et al., 2007). 80

81 Abstracts and Intra-symposium Fieldtrip During the late Miocene, central Argentina was an environment with widespread plains. These plains were extended in southern South America from 10 to 3 Ma, a period also known as the age of the plains. In this period, the area now occupied by La Pampa and Buenos Aires provinces was dominated by grasslands with temperate to warm temperate climates, favoring the development of the described fauna. The climate started to change at about 6 Ma, with a trend towards more arid conditions. Fig. 5. Sedimentologic log of the site where Laza (1982) originally described Attaichnus kuenzelii. Modified from Genise et al. (2013). 81

82 SLIC2013 Second Latin American Symposium on Ichnology Stop 1. Laza s section This section includes the original site where Laza (1982) studied Attaichnus kuenzelii (Fig. 2). At least three discrete paleosols can be recognized in the section, as revealed by the presence of three levels with peds (Figs. 5, 6A). The interval of the lower paleosol (P1, Fig. 5) includes massive clayey siltstone that passes upward to massive and cross-bedded siltstone. A 1.5 m thick cross-bedded set with tangential foresets (dipping up to 21 degrees) and an internal reactivation surface can be recognized (Fig. 6B). The upper and lower bounding surfaces of this set are not visible. Attaichnus kuenzelii, rhizoliths and vertebrate burrows are common and Coprinisphaera isp. and possible bee cells are rare (Figs. 6C to 6E). The uppermost horizon of P1 displays granular peds. Paleosol 2 (P2, Fig. 5), includes a lower horizon with crude horizontal or curved laminae and abundant mudstone intraclasts and carbonate nodules. Attaichnus kuenzelii, vertebrate burrows, and rhizoliths were identified at different depths in the section. Specimens of Coprinisphaera with greater cementation than those of the lowermost levels of P2 were found in the upper half of the paleosol. The uppermost horizon of P2 exhibits blocky peds. Paleosol 3 (P3, Fig. 2) is similar to the underlying one, except for the presence of prismatic and platy peds in the uppermost horizon. Overall carbonate cementation is lower in this paleosol, which is truncated by Holocene sandy deposits. Attaichnus kuenzelii Emended diagnosis. Large, sub-spherical, somewhat flattened to pear-shaped, massive structures that when weathered may show alveolar fillings or may look as empty chambers, surrounded by an external carbonate-cemented layer. A hole may be present in each pole and, in some cases, it may display inside the chamber a folded rim that is connected to a short vertical burrow. In other cases the burrow seems to continue inside the chamber. The external layer may show secondary holes near the poles, or unusually a rim around the upper hole. Chambers are commonly well separated and regularly distributed along the outcrop, or in groups of two or less commonly three specimens. Connections among chambers are unusual (from Genise et al. 2013). Laza (1982) recognized the presence of an interconnected chamber system occupying a large conical area, resembling an Atta s nest or mound. In a recent work, Genise et al. (2013) were not able to recognize this distribution. These authors remarked that interconnections among chambers were not observed, even when two chambers were in close proximity and tubular structures, some of them interpreted herein as tunnel casts, can be recognized among the chambers. Examined chambers are sub-spherical showing three basic outlines: the piriform, flattened, spherical (Figs. 7A to 7C). Equatorial diameter ranges from about 7 to 27 cm and height from 7 to 18 cm (Genise et al. 2013). Chambers show different internal morphologies such as massive, alveolar, and horizontally laminated (Fig. 7F). In some cases, chambers show holes on top and base and other secondary ones (Fig. 7E). In weathered specimens, holes on top and bottom are connected by an irregular, and in some cases widened, conduct that is poorly cemented. Some chambers are in connection with short, sinuous or straight, tunnels that mostly are basal or lateral (Fig. 8B). Some specimens are relatively close in vertical or horizontal exposures (Fig. 8A). In a single case, a small chamber inside a larger one was recognized (Fig. 8A). According to Genise et al. (2013), A. kuenzelii can be still attributed to Attini as originally proposed (Laza, 1982), but particularly to species of Acromyrmex or Trachymyrmex according to the new interpretation of its morphology. 82

83 Abstracts and Intra-symposium Fieldtrip Fig. 6. (A) Mosaic of the outcrop of the Cerro Azul Formation at the Laza s site (see Fig. 5). (B) Tangential foresets (arrowed) in the lower part of the section. (Medium-sized burrow fill (arrowed). Lamination in the lower part of the fill. Scale bar is 10 cm. (D) Probable bee cells (arrows) in horizontal position. (E) Coprinisphaera isp. Rhizoliths Cylindrical, vertical mostly unbranched and concentrically arranged structures, lacking any connection with chambers are considered herein as rhizoliths (Fig. 9C, 9D). They are very common in the outcrop, with an average diameter of about 3 cm. Vertebrate burrows. Large roughly cylindrical structures characterized by a laminated fill and oval crosssections are interpreted as vertebrate burrow fillings (Figs. 9A, 9B). The most distinctive 83

84 SLIC2013 Second Latin American Symposium on Ichnology aspect is the presence of mudstone laminae, especially in the lower part, which contrast with the massive, darker fabric of the hosting loess deposit. Burrow fills range in width from 0.17 to 1.05 m and maximum preserved length is about 2 m. Among the mammal fauna of the studied locality (Goin et al., 2000) and considering the body mass estimates by Vizcaíno and Fariña (1999) the likely producers are medium-sized fossorial mammals. In particular, the Dasypodidae (Macrochorobates sp., Chorobates villosissimus, Macroeuphractus sp.) and Rodentia (Lagostomus sp.) are the most likely producers (Genise et al., 2013). Fig. 7. Field views of Attaichnus kuenzelii. (A) Piriform chamber. (B) Flattened chamber. (C) Spherical (yellow arrow) and piriform (red arrow) chambers. (D) Plan view of one of the largest chambers. Scale is 10 cm. (E) A couple of two nearby chambers. (F) Weathered chamber with laminated fill (arrow). 84

85 Abstracts and Intra-symposium Fieldtrip Fig. 8. Field views of Attaichnus kuenzelii. (A) Three chambers in vertical section (yellow arrows) and a fourth smaller chamber inside the largest one (red arrow). (B) Chamber with a basal tunnel (arrow). (C) Weathered chamber (red arrow) and a dung beetle brood ball (yellow arrow) inside its filling. Note that there is another circular cross section to the lower right of the ball (probably a bee cell). Dung beetle brood balls. A single specimen of Coprinisphaera isp. was found in a vertical section of the upper palaeosol (P3). At the lowermost exposures of the Cerro Azul Formation in the mudflat surrounding the saline lake, it is possible to see specimens of Coprinisphaera ispp. One of these specimens occurs inside a weathered A. kuenzelii (Fig. 8C). The later are poorly cemented and are considered as younger than late Miocene in age (Genise et al. 2013). 85

86 SLIC2013 Second Latin American Symposium on Ichnology Fig. 9. Large vertebrate burrows and rhizoliths. (A) Oblique section of a vertebrateburrow fill (arrow) in a vertical exposure. (B) Plan view of a weathered vertebrate burrow fill (arrows). (C) Rhizoliths in plan view. (D) Blanched rhizolith in a vertical exposure (arrows). Scale bar is 10 cm. Bee cells and cell clusters Also at the lowermost exposures of the Cerro Azul Formation, mostly at mudflat surrounding the saline lake, occur different types of bee cells comparable to the ichnogenera Celliforma and Rosellichnus (Genise et al. 2013). Most of these specimens are poorly cemented and may exhibit organic remains, suggesting that they are younger than the hosting rock (Genise et al. 2013). Meniscate burrows. Although rare, meniscate burrows were observed both in the wall of A. kuenzelii chambers and in the hosting rock. Stop 2 We will walk toward the southwest along the coast of the saline lake for about 2.5 km looking essentially at sparse A. kuenzelii and vertebrate burrows in different preservational states. At stop 2 (Fig. 2), there is a higher concentration of chambers of A. kuenzelii although with a random distribution in vertical sections and horizontal beds. There are no areas with high density of chambers that could suggest that they are grouped composing discrete systems. Measured horizontal density usually is about 0.1 chambers by square meters, although a maximum density of 1.1 chambers by square meters (Genise et al. 2013). 86

87 Abstracts and Intra-symposium Fieldtrip References Albino, A. M. and Montalvo, C. I., Snakes from the Cerro Azul Formation (Late Miocene), Central Argentina. Journal of Vertebrate Paleontology 26, Albino, A. M., Brizuela, S. and Montalvo, C. I., New Tupinambis remains from the Late Miocene of Argentina and a review of the South American Miocene Teiids. Journal of Herpetology 40, Campbell, K. and Tonni, E., A new genus of teratorn from the Huayquerian of Argentina (Aves: Teratornithidae). Contributions in Sciences 330, Cenizo, M. M.,.Tambussi, C.P. and Montalvo, C. I Upper Miocene continental birds from Cerro Azul Formation in the Pampean region (south-central Argentina). Alcheringa: An Australasian Journal of Palaeontology 36, Cerdeño, E. and Montalvo, C. I., Los Mesotheriinae (Mesotheriidae, Notoungulata) del Mioceno superior de La Pampa, Argentina. Revista Española de Paleontología 16, Cerdeño, E. and Montalvo, C. I., Los Hegetotheriinae (Hegetotheriidae, Notoungulata) del Mioceno superior de la provincia de La Pampa, Argentina. Revista del Museo Argentino de Ciencias Naturales, n. s. 4, Chatterjee, S., Templin, R.J. and Campbell, K.E., The aerodynamics of Argentavis, the world s largest flying bird from the Miocene of Argentina. Proceedings of the National Academy of Sciences 104, Genise, J.F., Melchor, R.N., Sánchez, M.V. and González, M.G., Attaichnus kuenzelii revisited: A Miocene record of fungus-growing ants from Argentina. Palaeogeography, Palaeoclimatology, Palaeoecology 386, Goin, F., Montalvo, C. I. and Visconti, G., Los marsupiales (Mammalia) del Mioceno Superior de la Formación Cerro Azul (provincia de La Pampa). Revista del Museo Nacional de Ciencias Naturales, Estudios Geológicos 56, Laza, J., Signos de actividad atribuíbles a Atta (Myrmicidae, Hymenoptera) en el Mioceno de la Provincia de La Pampa, República Argentina. Significación paleozoogeográfica. Ameghiniana 19, Melchor, R. N., Visconti, G. and Montalvo, C. I., Late Miocene calcic vertisols from central La Pampa, Argentina. Resúmenes II Congreso Latinoamericano de Sedimentología y VIII Reunión Argentina de Sedimentología, Mar del Plata. Montalvo, C. I. and Casadío, S., Presencia del género Palaeoctodon (Rodentia, Octodontidae) en el Huayqueriense (Mioceno tardío) de la Provincia de La Pampa. 87

88 SLIC2013 Second Latin American Symposium on Ichnology Ameghiniana 25, Pascual, R., Pisano, J. and Ortega Hinojosa, E. J., Un nuevo Octodontidae (Rodentia, Caviomorpha) de la Formación Epecuén (Plioceno medio) de Hidalgo (provincia de La Pampa). Consideraciones sobre los Ctenomyinae Reig, 1958 y la morfología de sus molariformes. Ameghiniana 4, Pye, K., Aeolian dust and dust deposits. Academic Press, 334. pp. London. Spalletti, L. A., El loess y el problema de la identificación de las loessitas. Revista Museo de La Plata, nueva serie, Geología 11, Tsoar, H. and Pye, K., Dust transport and the question of desert loess formation. Sedimentolgoy 34, Urrutia, J. J., Montalvo, C. I. and Scillato Yané, G. J., Dasypodidae (Xenarthra, Cingulata) de la Formación Cerro Azul (Mioceno tardío) de la provincia de La Pampa, Argentina. Ameghiniana 45, Verzi, D., The dental evidence on the differentiation of the ctenomyine rodent (Caviomorpha, Octodontidae, Ctenomyinae). Acta Theriologica 44, Verzi, D. and Montalvo, C. I., The oldest South American Cricetidae (Rodentia) and Mustelidae (Carnivora): Late Miocene faunal turnover in central Argentina and the Great American Biotic Interchange. Palaeogeography, Palaeoclimatology, Palaeoecology 267, Verzi, D., Montalvo, C. I. and Deschamps, C., Biostratigraphy and biochronology of the Late Miocene of central Argentina: evidence from rodents and taphonomy. Geobios 41, Vezzosi, R. I First record of Procariama simplex Rovereto, 1914 (Phorusrhacidae, Psilopterinae) in the Cerro Azul Formation (upper Miocene) of La Pampa Province; remarks on its anatomy, palaeogeography and chronological range. Alcheringa: An Australasian Journal of Palaeontology 36, Visconti, G., Sedimentología de la Formación Cerro Azul (Mioceno superior) en la provincia de La Pampa. Unpublished doctoral Thesis (nr. 4084), Universidad de Buenos Aires. 203 pp. Buenos Aires. Visconti, G. and Montalvo, C. I., Mamíferos del Mioceno tardío en sedimentos redepositados de la Formación Cerro Azul. Resúmenes V Jornadas Pampeanas de Ciencias Naturales, p

89 Abstracts and Intra-symposium Fieldtrip Visconti, G., Montalvo, C. I., Cardonatto, M. C. and Púgener, L., Análisis sedimentológico e interpretación paleoambiental de la Formación Cerro Azul (Mioceno tardío) en el Valle Argentino, provincia de La Pampa. Comunicaciones VI Jornadas Pampeanas de Ciencias Naturales, Santa Rosa. Visconti, G., Melchor, R. N., Montalvo, C. I., Umazano, A. M. and E. E. de Elorriaga, Análisis litoestratigráfico de la Formación Cerro Azul (Mioceno Superior) en la provincia de La Pampa, Argentina. Revista de la Asociación Geológica Argentina 67, Vizcaíno, S, R. A. Fariña On the flight capabilities and distribution of the giant Miocene bird Argentavis magnificens (Teratornithidae). Lethaia

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