The Angosto del Moreno area, Eastern Cordillera, Jujuy province

Ordovician and Silurian rocks exposed in the western belt of the Eastern Cordillera of Jujuy Province will be discussed during the journey through the provincial road 16, which connects the Purmamarca Village with the Angosto del Moreno locality. Following stops refer to diverse geological aspects of the region.Fil: Moya, Maria Cristina. Universidad Nacional de Salta. Consejo de Investigacion; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; ArgentinaFil: Malanca, Susana. Universidad Nacional de Salta. Consejo de Investigacion; ArgentinaFil: Monteros, Julio A.. Universidad Nacional de Salta. Consejo de Investigacion; ArgentinaFil: Albanesi, Guillermo Luis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Ortega, Gladys del Carmen. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Buatois, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentin

Late Cambrian – Tremadocian faunas and events from Angosto del Moreno Section, Eastern Cordillera, Argentina

The Santa Victoria Group (SVG, late Upper Cambrian – Caradocian) comprises pre–Ashgillian Ordovician deposits of the Argentinean Eastern Cordillera. The most significant section of the SVG in the western flank of the Eastern Cordillera is located in the Angosto del Moreno area (Figure 1a, b). At this locality, the SVG unconformably overlies the Mesón Group (Cambrian s.l.), and unconformably underlies Cretaceous rocks (Yacoraite Formation). Upper Cambrian to lower Lower Ordovician units are separated from upper Lower to Middle Ordovician units (Parcha and Sepulturas formations) by the Tumbaya unconformity (Figure 2). The Angosto del Moreno Section of the SVG is exceptional in terms of the quality of exposures, continuity of deposits, richness of fossils, and accessibility. Diverse aspects concerning the Ordovician geology of this study area have been discussed by Moya et al. (1994, 1998), Moya and Albanesi (2000), Moya and Monteros (2000), Malanca and Brandán (2000), and Gómez Martínez et al. (2002). Previous data and recent paleontological collections enable a preliminary biostratigraphic scheme (Figure 2) for the Upper Cambrian to Tremadocian units of the SVG. A synthesis of the sequence stratigraphy and depositional environments of these units is given by Buatois et al. (this volume).Fil: Moya, Maria Cristina. Universidad Nacional de Salta. Consejo de Investigacion; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; ArgentinaFil: Malanca, Susana. Universidad Nacional de Salta. Consejo de Investigacion; ArgentinaFil: Monteros, Julio A.. Universidad Nacional de Salta. Consejo de Investigacion; ArgentinaFil: Albanesi, Guillermo Luis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Ortega, Gladys del Carmen. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Buatois, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; Argentin

Paleoenvironmental and sequence stratigraphic framework of the Cambrian–Ordovician transition in the Angosto del Moreno area, Northwest Argentina

The Cambrian–Ordovician transition has been the focus of a series of biostratigraphic studies in Northwest Argentina (e.g., Benedetto, 1977; Aceñolaza, 1983; Aceñolaza and Aceñolaza, 1992; Rao and Hunicken, 1995; Tortello and Aceñolaza, 1999). However, there is a remarkable absence of detailed stratigraphic sections and only a few studies deal with the associated sedimentary facies and the sequence stratigraphic framework of the Cambrian–Ordovician successions (Moya, 1998; Buatois and Mángano, in press). This has historically precluded a more accurate biostratigraphic zonation and placing of the Cambrian–Ordovician boundary. The aim of this paper is, therefore, to provide a paleoenvironmental and sequence stratigraphic framework for the Cambrian–Tremadocian succession exposed at the Angosto del Moreno area, in the southwest region of the Eastern Cordillera, Jujuy Province. Although this paper is focused on this particular section, information from other areas in Eastern Cordillera has been used for the recognition of allostratigraphic surfaces and stratal stacking patterns. We emphasize that integrated paleontologic (body and trace fossils), sedimentologic and sequence stratigraphic studies are essential in biostratigraphy. Paleontological data and biostratigraphic analysis is presented in Moya et al. (this volume).Fil: Buatois, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; ArgentinaFil: Moya, Maria Cristina. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; ArgentinaFil: Mangano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Correlación Geológica. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Departamento de Geología. Cátedra Geología Estructural. Instituto Superior de Correlación Geológica; ArgentinaFil: Malanca, Susana. Universidad Nacional de Salta. Facultad de Ciencias Naturales; ArgentinaFil: Albanesi, Guillermo Luis. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Ortega, Gladys del Carmen. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Museo de Paleontología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentin

Sediment disturbance by Ediacaran bulldozers and the roots of the Cambrian explosion

Se han documentado fósiles de rastros de excavadoras de sedimentos en los estratos ediacaranos terminales del Grupo Nama en Namibia, donde se encuentran en el miembro Spitskop de la Formación Urusis (subgrupo Schwarzrand). Consisten en fósiles de trazas unilobadas a bilobadas horizontales a subhorizontales que describen garabatos, círculos y, más raramente, espirales y meandros abiertos, y que muestran una estructura interna indicativa de relleno activo. Su presencia sugiere que la explotación del ecoespacio infaunal poco profundo por parte de bilateros relativamente grandes ya estaba en marcha en los albores del Fanerozoico. El excavado eficiente sugiere que el desarrollo de la espina dorsal está muy probablemente relacionado con el aumento del tamaño del cuerpo de los metazoos. Estos fósiles en trazas son los primeros representantes claros hasta ahora registrados del arrastre de sedimentos, actividad que puede haber tenido un impacto negativo en las comunidades de alimentación en suspensión y/o de osmotrofos, así como en las esteras, lo que representa los primeros ejemplos de ingeniería de ecosistemas y amensalismo de grupos tróficos. La aparición de bulldozers de sedimentos puede haber promovido el establecimiento de gradientes en la distribución horizontal y vertical de material orgánico en relación con entornos espacialmente heterogéneos en el fondo marino en un momento crítico de la evolución de la Tierra.Trace fossils of sediment bulldozers are documented from terminal Ediacaran strata of the Nama Group in Namibia, where they occur in the Spitskop Member of the Urusis Formation (Schwarzrand Subgroup). They consist of unilobate to bilobate horizontal to subhorizontal trace fossils describing scribbles, circles and, more rarely, open spirals and meanders, and displaying an internal structure indicative of active fill. Their presence suggests that exploitation of the shallow infaunal ecospace by relatively large bilaterians was already well underway at the dawn of the Phanerozoic. Efficient burrowing suggests coelom development most likely linked to metazoan body-size increase. These trace fossils are the earliest clear representatives so far recorded of sediment bulldozing, an activity that may have had a negative impact on suspension-feeding and/or osmotroph communities, as well as on matgrounds, representing early examples of ecosystem engineering and trophic-group amensalism. The occurrence of sediment bulldozers may have promoted the establishment of gradients in horizontal and vertical distribution of organic material in connection with spatially heterogeneous environments on the sea floor at a critical time in Earth evolution.• Natural Sciences and Engineering Research Council (NSERC) Discovery. Grants 311726-05/13 y 311727-05/15, para Louis Alberto Buatois y Maria Gabriela Mángano • Palaeontological Scientific Trust (Sudáfrica). Ayuda a John Almond • Ministerio de Ciencia e Innovación y Fondo Europeo de Desarrollo Regional (FEDER). Subvención CGL-2012-37237, para Sören JensenpeerReviewe

Infaunalization and resource partitioning during the Mesozoic marine revolution

Infaunalization has been regarded as representing a response to increased predation pressures and is therefore central to the Mesozoic marine revolution, which gives pre-eminence to the role that enemy-directed evolution has played as a driving force of biotic change. Our ichnologic compilation from 39 Middle Triassic to Late Jurassic shallow-marine siliciclastic units allows us to evaluate the vertical partitioning of the infaunal ecospace through the application of the ichnoguild concept. This study shows that infaunal communities experienced a marked increase in ecospace utilization during the Early Jurassic, reaching a plateau during the rest of the Jurassic. This trend is expressed by an increase in the maximum number of ichnoguilds per community and per tier and in the number of ichnotaxa per ichnoguild. This pattern shows important partitioning of the infaunal ecospace into a series of tiers and that several organisms were able to exploit the same resources available at discrete sediment zones below the sea bottom. The increase in the maximum number of ichnoguilds per community and per tier suggests that niche partitioning was a key factor in a more efficient use of the infaunal ecospace and in driving alpha diversity. However, the increase in the number of ichnotaxa per ichnoguild indicates that ichnoguilds were packed with organisms exploiting similar resources, arguing against the role of competitive exclusion in structuring communities. Because several episodes of predation increase took place during the Mesozoic, an unequivocal link between predation pressures and infaunalization cannot be demonstrated empirically.Fil: Buatois, Luis Alberto. University of Saskatchewan; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mángano, M. Gabriela. University of Saskatchewan; CanadáFil: Desai, Bhawanisingh. Pandit Deendayal Energy University; IndiaFil: Carmona, Noelia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Burns, Fiona. Firmground; AustraliaFil: Meek, Dean. University of Saskatchewan; CanadáFil: Eglington, Bruce. University of Saskatchewan; Canad

Sedimentological and ichnological analyses of the continental to marginal-marine Centenario Formation (Cretaceous), Neuquén Basin, Argentina: Reservoir implications

The upper Valanginian – lower Aptian Centenario Formation is a significant producer of oil and gas in the Neuquén Basin, western Argentina. This formation is located exclusively in the subsurface of the eastern and northeastern Neuquén Basin, and is 450–1000 m thick. The Centenario Formation laterally interfingers with the Agrio Formation. Previous studies addressing the paleogeographic history of the Centenario Formation are scarce, and a comprehensive geological model has yet to be put forward. The current study scrutinizes the Centenario Formation, especially its lower member, within the northeastern Neuquén Basin. The study area includes the Cerro Hamaca Oeste, Señal Cerro Bayo, and Volcán Auca Mahuida oilfields operated by Yacimientos Petrolíferos Fiscales (YPF). Sedimentological and ichnological core data, geophysical well logs, and petrographic thin sections have been utilized to construct a geological model. Eleven sedimentary facies and three facies associations have been identified from the core dataset, providing insights into the paleoenvironmental settings and their stresses on infaunal colonization. Basin-margin deposits from the northeastern part of the study region were formed in continental environments, comprising ephemeral fluvial channel complexes and floodplains, and are ichnologically represented by rare Skolithos and common rhizoliths. The central part of the study area is interpreted as recording deposition in ephemeral lakes, river-dominated lake deltas, and coastal lagoons and sabkhas, and is represented by a combination of stressed expressions of both the Skolithos and Scoyenia Ichnofacies. River-dominated, storm-influenced delta deposits are located towards the southwestern limit of the study area, and are ichnologically represented by the Skolithos and depauperate Cruziana Ichnofacies. Deltaic deposits gradually transition into the basinal facies of the Agrio Formation to the west. Overall sedimentologic characteristics suggest semi-arid to arid climatic conditions during deposition.Fil: Shchepetkina, Alina. Universidad Nacional de Río Negro; Argentina. University of Saskatchewan; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ponce, Juan Jose. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carmona, Noelia Beatriz. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mángano, M. Gabriela. University of Saskatchewan; CanadáFil: Buatois, Luis Alberto. University of Saskatchewan; Canadá. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ribas, Soledad. YPF - Tecnología; ArgentinaFil: Villar Benvenuto, Marcela Celeste. YPF - Tecnología; Argentin

Trazas fósiles y dinámica sedimentaria de los lagos carboníferos de la Cuenca Paganzo

Fil: Buatois, Luis Alberto. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Ichnotaxobases for bioerosion trace fossils in bones

Bioerosion trace fossils in bones are defined as biogenic structures that cut or destroy hard bone tissue as the result of mechanical and/or chemical processes. Under the premise that their paleoecological potential can completely be realized only through correct taxonomic assignment, this work focuses on the methodology for naming these biogenic structures. Thus, we propose the following ichnotaxobases in order to assist in naming trace fossils in bones: general morphology, bioglyphs, filling, branching, pattern of occurrence, and site of emplacement. The most common general morphologies are: pits and holes (borings); chambers; trails; tubes; channels (canals); grooves; striae; and furrows. The main types of bioglyphs are grooves and scratches, which may display different arrangements, such as parallel and opposing, or arcuate paired. The nature of the fill may help recognition of the origin, composition, and relationship with the surrounding sediment, as well as processes of destruction or consumption of bony tissue. The structure and layout of the filling, such as meniscate backfill or pelleted filling, offer information about the bioeroding processes. Branching structures on cortical bone are present in canals and furrows. Where the trace penetrates spongy bone, branching structures are forming tunnels that may connect internal chambers. The common patterns of occurrence are individual, paired, grouped, overlapping, lined, and arcuate. The site of emplacement may be in cortical bone, spongy bone, articular surfaces, internal bone microstructures, and external bone anatomical structures. The use of substrate as an ichnotaxobase is problematic, but as biological substrate, bone itself is a valuable source of information for paleoecologic and ethologic inferences. Given the paleontological importance of bioerosion trace fossils in bones, we underscore interactions between ichnology and other sciences, such as forensic entomology, archaeology, paleoecology, and taphonomy.Fil: Pirrone, Cecilia Anabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Buatois, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Saskatchewan; CanadáFil: Bromley, Richard G.. Statens Naturhistoriske Museum; Dinamarc

Gyrophyllites cristinae isp. nov. from lower ordovician shallow-marine deposits of northwest Argentina

The lower Paleozoic marine siliciclastic succession of the Central Andean Basin, northwestern Argentina, provides a valuable record of the onset of the Great Ordovician Biodiversification Event in western Gondwana. A new ichnospecies of rosette trace fossil, Gyrophyllites cristinae, is documented from lower and upper Tremadocian (Tr1 and Tr2) deposits of this basin. It is characterized by five to six non-overlapping petaloid lobes and can be easily differentiated from the other four formally defined ichnospecies. Gyrophyllites cristinae occurs at the top of hummocky cross-stratified sandstone regularly interbedded with mudstone. These deposits are interpreted as reflecting the alternation of high-energy storm events and low-energy fair-weather conditions immediately below the fair-weather wave base, representing deposition in offshore transition environments. Gyrophyllites has been traditionally interpreted as the product of worms of uncertain taxonomic affinity that mined the sediment in search for food (fodinichnia). The occurrence of Gyrophyllites cristinae in these Ordovician deposits records post-storm colonization. Storms may have increased oxygenation and supplied fresh organic detritus that were exploited by worm-like, surface detritus- or shallow deposit-feeders exploring the uppermost silt-rich fine-grained sediments.Fil: Muñoz, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. University of Saskatchewan; CanadáFil: Mangano, Maria Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Buatois, Luis Alberto. University of Saskatchewan; Canad

A New Ichnospecies of Cubiculum from Upper Cretaceous Dinosaur Bones in Western Argentina

The new ichnospecies Cubiculum levis is described as a bowl-shaped bioerosion trace fossil in dinosaur bone from the Upper Cretaceous of western Argentina. The systematic description is based on specific ichnotaxobases for bioerosion trace fossils in bones. The main characteristics of the new ichnospecies are its general bowl-shaped morphology with marked concavity of the flanks and bottom, marked constriction of walls in the upper area, and the absence of bioglyphs in the interior surface. To establish a hierarchical approach to the taxonomy of Cubiculum, we propose an emended diagnosis for this ichnogenus. Based on comparative analysis with structures of fossil pupal chambers and results of actualistic experiments with carrion insects, the ethology of C. levis is interpreted as Pupichnia. Paleoenvironmental conditions at the paleontological site, taphonomic data and the morphology of C. levis indicate a continental arthropod producer with the biological and anatomical ability to bore bone. The producer was probably a Cretaceous coleopteran with a heavily sclerotized body and well-developed biting mouthparts. We emphasize the importance of establishing paleoethologic and paleobiologic inferences based on testable data provided by multiple sources, such as biology, physiology, sedimentology, and forensic sciences. Finally, we cite some relevant reports of traces fossils in bones interpreted as pupal chambers and we discuss the conflicting interpretations of their producers and ecological significance.Fil: Pirrone, Cecilia Anabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Buatois, Luis Alberto. University of Saskatchewan; CanadáFil: Gonzalez Riga, Bernardo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentin