Bivalves and brachiopods in the Carboniferous - Early Permian of Argentine Precordillera: Diversification and faunal turnover in Southwestern Gondwana

Diversification patterns and faunistic turnovers of bivalves and brachiopods through the Carboniferous - Early Permian interval in the central western Argentinian basins are analyzed and compared with the global events proposed in former studies. This study reveals a generalized increase of bivalves, at familiar and generic levels, through three time intervals, i.e., Early Carboniferous (Tournaisian-Visean), Late Carboniferous (Bashkirian-Kasimovian) and Early Permian (Asselian-Sakmarian), while the brachiopod diversity seems to remain stable from the Late Carboniferous to the Early Permian. The trends recognized in the faunistic diversity appear to be closely related to the palaeoclimatic, palaeogeographic and palaeotectonic evolution at the Southwestern Gondwana margin. Highly stressing environmental changes in the Early Carboniferous, resulting fundamentally from the development of glacial conditions, may account for the lowest faunistic diversity recorded. Particular stress conditions, such as the nutrient availability, temperature and oxygen level, would have mainly affected the brachiopod faunas that evidence the lowest diversity recognized in the interval studied. At the Visean-Serpukovian boundary, the Late Palaeozoic marine record of the Precordillera shows a major break linked to a globally recognized glacial maximum, whereas an important faunistic turnover is mainly identified in the brachiopod faunas at the beginning of the Late Carboniferous. The more stable, less stressing environmental situation developed during the Late Carboniferous-Early Permian postorogenic sedimentation is also reflected by the different faunal assemblages studied. The Late Carboniferous was characterized by postglacial transgressions. During this time local rebound, a continuous increase of the diversity and an important faunal turnover, which mainly affected the brachiopod faunas, were recorded. These faunal trends may be related to the Early Permian climatic amelioration that affected the central western Argentinian basins. The subsequent Permian transgressive events, which produced new areas of potential spreading for the benthic fauna, allowed its increase and diversification, much better reflected by the bivalve assemblages

Enhancement of Paleozoic Geosites of the Jagüé Bolson for its Integration in the Touristic Product of Laguna Brava, La Rioja Province,Argentina

El Bolsón de Jagüé en el noroeste de la provincia de La Rioja (departamento Vinchina), guarda un importante registro geológico de la Era Paleozoica, particularmente de los períodos Devónico, Carbonífero y Pérmico (419-252 Ma). Este intervalo estuvo caracterizado por fuertes contrastes climáticos que variaron desde condiciones frías de tundra, pasando por climas templados húmedos hasta desérticos, en un paisaje marcadamente cambiante con frecuentes ingresiones marinas, afectado por el tectonismo y volcanismo que caracterizaron este margen de Gondwana. El objetivo del presente trabajo es la puesta en valor de sitios geológico/paleontológicos (geositios) del Bolsón de Jagüé, con el fin de integrarlos a un producto turístico existente: Laguna Brava. Se aplicaron criterios científicos y turísticos, utilizando una metodología que contempló relevamiento de fuentes secundarias, análisis del marco legal y aplicación de fichas elaboradas para este caso. De los geositios analizados sólo un número reducido, además de su importancia científica, reúne una serie de aspectos (accesibilidad, cercanía al circuito turístico existente, valor paisajístico, conservación, entre otros), que permitirían su integración al producto turístico Laguna Brava. Conclusiones preliminares indican que el registro fosilífero y la diversidad geológica convierten al Bolsón de Jagüé en un área con potencial para el turismo educativo y científico.The Bolsón de Jagüé in the northwest of the province of La Rioja (district of Vinchina), keeps an important geological record of the Paleozoic Era, particularly of the Devonian, Carboniferous, and Permian periods (419-252 Ma). This interval was characterized by strong climatic contrasts ranging from cold tundra to desert climates, going through humid and moderate climates, in a markedly changing landscape with frequent marine ingressions, affected by the tectonism and volcanism that characterized this Gondwana margin. The purpose of this work is the enhancement of geological and paleontological sites (geosites) of the Bolsón de Jagüé, in order to integrate them into an existing tourism product: Laguna Brava. Scientific and touristic criteria were applied, using a methodology that included a survey of secondary sources, analysis of the legal framework, and application of files prepared for this case. In addition to its scientific importance, only a small number of the geosites analyzed, brings together a number of aspects (accessibility, proximity to the existing tourist circuit, landscape value, conservation, among others), which would allow its integration into the Laguna Brava tourism product. Preliminary conclusions indicate that fossil record and geological diversity make the Bolsón de Jagüé an area with potential for educational and scientific tourism.Fil: Salvadeo, Victoria. Universidad Nacional de La Rioja; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cisterna, Gabriela Adriana. Universidad Nacional de La Rioja; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vaccari, Norberto Emilio. 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; Argentin

Early Permian marine carbonate sequences in Antofagasta, northern Chile

Se analizan las sucesiones carbonáticas de las formaciones Cerro El Árbol y Cerros de Cuevitas, en la Depresión central de Antofagasta, norte de Chile. Las mismas están caracterizadas por una asociación de invertebrados marinos compuesta, en general, por braquiópodos, bivalvos, gastrópodos, crinoideos y briozoos, siendo el braquiópodo Kochiproductus Dunbar el elemento dominante. La presencia de este género, de amplia distribución mundial en secuencias pérmicas, sería clave para encontrar la posible vinculación de esta región con las cuencas clásticas del centro oeste de Argentina. Si bien la fauna del norte de Chile presenta claras afinidades con aquellas de las cuencas de Bolivia y Perú, su composición no es exactamente equivalente, siendo además marcadamente menos diversa. El conocimiento taxonómico aquí alcanzado indica que esta fauna podría representar una asociación de mezcla, que combinaría los elementos típicamente tetianos que caracterizan a las cuencas del norte, con aquellos gondwánicos. En términos bioestratigráficos, esta asociación podría también ser considerada intermedia entre las faunas más antiguas del Carbonífero tardío-Pérmico temprano del centro oeste de Argentina y las más jóvenes del Pérmico de Bolivia y Perú.The carbonate successions of the Cerro El Árbol and Cerros de Cuevitas formations in the central region of Antofagasta are herein studied. These stratigraphic units are characterized by an invertebrate marine fossil assemblage integrated by brachiopods, bivalves, gastropods, crinoids and bryozoans, in which the brachiopod Kochiproductus Dunbar is the dominant component. This genus, widely known in the Permian sequences of the world, can be considered a key to understand the possible connection between northern Chile and the central western Argentinean basins. Although the fauna studied shows clear affinities with those from Bolivia and Perú, it is notably less diverse and its composition appears to be not exactly equivalent. The taxonomic knowledge reached, indicates that this fauna, particularly brachiopods and bivalves, would represent a mixed-assemblage. From a biostratigraphic perspective, the fauna of northern Chile could be considered intermediate between the oldest Late Carboniferous-Early Permian faunas of central western Argentinian basins and the younger ones from Bolivia and Perú.Fil: Cisterna, Gabriela Adriana. Universidad Nacional de la Rioja; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sterren, Andrea Fabiana. 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: Niemeyer, Hans R.. Universidad catolica del Norte; Chil

El registro más austral de la Fauna Aseptella-Tuberculatella / Rhipidomella-Micraphelia (Serpukhoviano tardío-Bashkiriano) en la cuenca Calingasta-Uspallata, Argentina

El registro más austral de la Fauna Aseptella-Tuberculatella / Rhipidomella-Micraphelia (Serpukhoviano tardío-Bashkiriano) en la cuenca Calingasta-Uspallata, Argentina. La Formación Agua del Jagüel aflora en el sector más austral de la cuenca de Calingasta-Uspallata, centro-oeste de Argentina. La parte inferior de esta unidad se caracteriza por una secuencia glacigénica compuesta por diamictitas y pelitas con clastos dispersos. En esta última se reconocen elementos de la fauna Aseptella-Tuberculatella/Rhipidomella-Micraphelia (Fauna AT/RM), tales como los braquiópodos Rhipidomella discreta Cisterna, Micraphelia indianae Simanauskas y Cisterna, Orbiculoidea? sp., los gastrópodos Murchisonia? sp. y Glabrocingulum (Stenozone)? sp., el bivalvo Nuculanidae indet., corales rugosos, y fragmentos indeterminados de hyolithes y nautiloideos. El hallazgo de esta fauna resulta importante desde el punto de vista paleoambiental y bioestratigráfico. La Fauna AT/RM es característica de ambientes restringidos, con relativamente bajas concentraciones de oxígeno y nutrientes en el fondo marino, lo cual es consistente con secuencias glacimarinas en costas tipo fiordos sugeridas para la Formación Agua del Jagüel. La baja diversidad relativa de la fauna en esta unidad comparada con la definida en la Formación El Paso, ubicado más al norte en la misma cuenca, podría sugerir sectores relativamente más restringidos para la colonización bentónica, relacionados con el aislamiento del paleovalle de las aguas oceánicas. Las pelitas postglaciales con invertebrados marinos del Serpukhoviano tardío-Bashkiriano se habrían depositado en sectores relativamente restringidos (paleofiordos) de la cuenca de Calingasta-Uspallata, como así también en ambientes de plataforma. La transgresión marina sobre las distintas configuraciones costeras y la disponibilidad de nutrientes y oxígeno en la columna de agua habrían propiciado el desarrollo de faunas con diferente composición taxonómica y estructura paleoecológica (Faunas AT/RM y Levipustula), en el mismo intervalo temporal. Los datos radimétricos en la Formación Agua del Jagüel y la información paleontológica en la sucesión glacial-postglacial dentro de la cuenca (invertebrados marinos, palinomorfos y plantas) constituyen las herramientas más importantes para ajustar la edad de la transgresión. Esta información complementa el esquema propuesto para las secuencias carboníferas en todo el centro oeste de Gondwana, pero no es suficiente para precisar las edades dentro del intervalo Serpukhoviano tardío-Bashkiriano.The Agua del Jagüel Formation crops out in the southernmost part of the Calingasta-Uspallata basin, in central western Argentina. The lower part of the unit is characterized by a glacigenic sequence with diamictites and mudstones with dropstones. In the latter, elements of the Aseptella- Tuberculatella/Rhipidomella-Micraphelia Fauna (AT/RM Fauna), such as the brachiopods Rhipidomella discreta Cisterna, Micraphelia indianae Simanauskas and Cisterna and Orbiculoidea? sp., the gastropods Murchisonia? sp., and Glabrocingulum (Stenozone)? sp., the bivalve Nuculanidae indet., rugose corals, and indeterminate fragments of nautiloids and hyolithids, have been identified. The importance of this fauna mainly resides in its paleoenvironmental and biostratigraphic implications. AT/RM Fauna is characteristic of restricted environments with relatively low concentrations of oxygen and nutrients in the seafloor, which is consistent with the glaciomarine sequences in fjord-type coasts suggested for the Agua del Jagüel Formation. The relatively lowdiversity of the fauna in this unit compared to that defined in the El Paso Formation, located further north in the basin, might suggest more restricted sectors for benthic colonization, related to the paleovalle?s isolation from oceanic waters. The postglacial mudstones with marine invertebrate faunas of late Serpukhovian-Bashkirian age would have been deposited in relatively restricted (palaeofjord) part of the Uspallata-Calingasta basin as well as in open shelf environments. The marine flooding over drastically different coast configurations and the availability of nutrient and oxygen in the watercolumn would have propitiated the development of faunas with important differences in the taxonomic composition and the paleoecological structure (AT/RM and Levipustula Faunas) occurring at the same time interval. Radiometricdata in Agua del Jagüel Formation and paleontological records in the glacial-postglacial sedimentary succession in the basin (marine invertebrate faunas, palynomorphs and plants) are the most important tools to adjust the timing of the postglacial transgression. This information herein presented complements the scheme proposed for the Carboniferous sequences throughout the central western of Gondwana but is not sufficient to assign a more precise age of the faunastudied within the late Serpukhovian-Bashkirian interval.Fil: Sterren, Andrea Fabiana. 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: Cisterna, Gabriela Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Rioja. Departamento de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: López-Gamundí, Óscar. PI Consultants; Estados UnidosFil: Vergel, Maria del Milagro. 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; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentin

Glaciomarine sequence stratigraphy in the Mississippian Río Blanco Basin, Argentina, southwestern Gondwana: Basin analysis and palaeoclimatic implications for the Late Paleozoic Ice Age during the Tournaisian

The Late Paleozoic Ice Age (LPIA) has been well recorded in the uppermost Mississippian?Pennsylvanian of Gondwana. Nevertheless, little is known about the temporal and geographic dynamics, particularly during the early Mississippian. We report on exceptional Tournaisian glaciomarine stratigraphic sections from central Argentina (Río Blanco Basin). Encompassing c. 1400 m, these successions contain conspicuous glacigenic strata with age constraints provided bypalaeontological data and U/Pb detrital zircon age spectra. A variety of marine, glaciomarine and fan-deltaic environments indicate relative sea-level variations mainly associated with tectonism and repetitive cycles of glacial activity. Provenance analysis indicates a source from the Sierras Pampeanas basement located to the east. Fifteen sequences were grouped into threedepositional models: (1) Transgressive Systems Tracts (TST) to Highstand Systems Tracts (HST) sequences unaffected by glacial ice; (2) Lowstand Systems Tracts (LST) to TST and then to HST with glacial influence; and (3) non-glacial Falling-Stage Systems Tracts (FSST) to TST and HST. The glacial evidence indicates that the oldest Mississippian glacial stage of the LPIA in southwestern Gondwana is constrained to the middle Tournaisian. In contrast with previous descriptions of Gondwanan coeval glacial records, our sequence analysis confirms complex hierarchical climate variability, rather than a single episode of ice advance and retreat.Fil: Ezpeleta, Miguel. 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. Universidad Nacional de La Rioja; ArgentinaFil: Rustán, Juan José. 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. Universidad Nacional de La Rioja; ArgentinaFil: Balseiro, Diego. 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: Davila, Federico Miguel. 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: Dahlquist, Juan Andrés. 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: Vaccari, Norberto Emilio. 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. Universidad Nacional de La Rioja; ArgentinaFil: Sterren, Andrea Fabiana. 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: Prestianni, Cyrille. Royal Belgian Institute of Natural Sciences; BélgicaFil: Cisterna, Gabriela Adriana. 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. Universidad Nacional de La Rioja; ArgentinaFil: Basei, Miguel. Universidade de Sao Paulo; Brasi

"Levipustula Fauna" in central-western Argentina and its relationships with the Carboniferous glacial event in the southwestern Gondwanan margin

The Levipustula Fauna (included in the Levipustula levis Zone) is a relatively diversified fossil assemblage composed of brachiopods, bivalves, bryozoans, gastropods, and crinoids. This fauna usually is associated with glaciomarine sequences related to the Carboniferous glacial event that affected the southwestern Gondwanan margin. The Levipustula Fauna has been identified in different units (e.g., Hoyada Verde, La Capilla, Leoncito, and Yalguaraz Formations) exposed in the Calingasta-Uspallata Basin. The Hoyada Verde Formation, herein proposed as a key section, contains the most complete record of the Levipustula Fauna. A detailed compositional, taphonomic, and paleoecological study of this section allows us to propose two associations within the so-called Levipustula Zone: the "Intraglacial Levipustula Fauna," present in the diamictite-dominated lower part, and the "Postglacial Levipustula Fauna," dominant in the upper part of section. The fossils of the "Intraglacial Levipustula Fauna" are scarce and poorly diversified. These two features suggest environmentally stressed conditions, probably related to low temperatures in areas close to glaciers. In comparison, the "Postglacial Levipustula Fauna," relatively more abundant and diverse, exhibits compositional variations that could be explained by paleoenvironmental changes associated with fluctuations in substratum and food supply, such as those identified in modern ecosystems. The identification of the "Intraglacial Levipustula Fauna" and the "Postglacial Levipustula Fauna" may constitute a new tool for understanding the particular relationship between faunal assemblages and climatic variations linked to the Gondwanan glaciation in the Calingasta-Uspallata Basin. Also, the new "Intraglacial Levipustula Fauna" identified in the Hoyada Verde Formation would have biostratigraphical and paleogeographical implications in intra-and interbasinal correlations.Fil: Cisterna, Gabriela Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación Miguel Lillo; ArgentinaFil: Sterren, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones Paleobiológicas; Argentin

Late Carboniferous postglacial brachiopod faunas in the Southwestern Gondwana margin

The glaciomarine sediments related to the Late Paleozoic Ice Age (LPIA), have an excellent stratigraphic record in Argentina, particular those associated to the Late Carboniferous glacial episode identified along the southwestern margin of South America: Bolivia (Tarija Basin), west central Argentina (Calingasta-Uspallata Basin) and Patagonia (Tepuel-Genoa basins). The aim of this contribution is mainly a biostratigraphy update of the carboniferous brachiopod faunas that occur in the earliest postglacial interval (late Serpukhovian-Bashkirian) in the west central Argentina (i.e. Levipustula and Aseptella-Tuberculatella/Rhipidomella-Micraphelia) and its regional correlation with those equivalents in the nearby basins. Components of these faunas are recognized from the Bolivia to Argentine Patagonia and the compositional variations exhibited by them appear to be principally controlled by a paleolatitudinal factor. The affinities showed by the postglacial faunas from the Calingasta-Uspallata Basin and the faunal assemblages that integrate the Lanipustula and Tuberculatella biozones in Patagonia, differ from the strong contrast proposed by other authors, based on the paleogeographical position of Patagonia in the Late Paleozoic. Paleoecological studies focuseon the paleoenvironmental controls related with the glacial dynamic are suggested to understand the complex relationship between these postglacial faunal.Fil: Cisterna, Gabriela Adriana. Universidad Nacional de la Rioja. Museo de Cs. Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Sterren, Andrea Fabiana. 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; Argentin

Bivalves and brachiopods in the Carboniferous - Early Permian of Argentine Precordillera: Diversification and faunal turnover in Southwestern Gondwana

Diversification patterns and faunistic turnovers of bivalves and brachiopods through the Carboniferous - Early Permian interval in the central western Argentinian basins are analyzed and compared with the global events proposed in former studies. This study reveals a generalized increase of bivalves, at familiar and generic levels, through three time intervals, i.e., Early Carboniferous (Tournaisian-Visean), Late Carboniferous (Bashkirian-Kasimovian) and Early Permian (Asselian-Sakmarian), while the brachiopod diversity seems to remain stable from the Late Carboniferous to the Early Permian. The trends recognized in the faunistic diversity appear to be closely related to the palaeoclimatic, palaeogeographic and palaeotectonic evolution at the Southwestern Gondwana margin. Highly stressing environmental changes in the Early Carboniferous, resulting fundamentally from the development of glacial conditions, may account for the lowest faunistic diversity recorded. Particular stress conditions, such as the nutrient availability, temperature and oxygen level, would have mainly affected the brachiopod faunas that evidence the lowest diversity recognized in the interval studied. At the Visean-Serpukovian boundary, the Late Palaeozoic marine record of the Precordillera shows a major break linked to a globally recognized glacial maximum, whereas an important faunistic turnover is mainly identified in the brachiopod faunas at the beginning of the Late Carboniferous. The more stable, less stressing environmental situation developed during the Late Carboniferous-Early Permian postorogenic sedimentation is also reflected by the different faunal assemblages studied. The Late Carboniferous was characterized by postglacial transgressions. During this time local rebound, a continuous increase of the diversity and an important faunal turnover, which mainly affected the brachiopod faunas, were recorded. These faunal trends may be related to the Early Permian climatic amelioration that affected the central western Argentinian basins. The subsequent Permian transgressive events, which produced new areas of potential spreading for the benthic fauna, allowed its increase and diversification, much better reflected by the bivalve assemblages

Late paleozoic brachiopod zonation in west and east-central Argentina and its correlation with other south american basins

Brachiopods, one of the most abundant and diversified groups in the late Paleozoic benthic marine communities, are not particularly time-sensitive fossils but have been considered good tools for characterizing, correlating and assigning a relative age to the sedimentary successions. Although the Argentinian brachiopod faunas are among the better known for the late Paleozoic of South America, the absence of more precise biostratigraphic markers, the scarce radiometric data available and the strong faunal provincialism, prevent developing a high-resolution scheme. However, the marine stratigraphic record of the Mississippian–Pennsylvanian in central-western Argentina, considered to be one of the most complete in the region, allows the confection of a brachiopod zonation that provides the basis for correlations with other South American basins. Five brachiopod zones are proposed, namely Azurduya chavelensis (Tournaisian–Visean) restricted to the Río Blanco Basin and also identified in northern Chile; Levipustula levis (late Serpukhovian–early Bashkirian), typically associated to the postglacial transgression of the second glacial episode identified in the region, and also recorded from the Bolivian Tarija Basin; Marginovatia peregrina-Maemia tenuiscostata (late Bashkirian–early Moscovian), a zone of local value defined in the Barreal Hill of the Calingasta-Uspallata basin; Tivertonia jachalensis-Streptorhynchus inaequiornatus (Moscovian), the most widely distributed and diversified in the Precordillera, developed in relatively warm temperate conditions; and the youngest Costatumlulus amosi (?Sakmarian–?Artinskian), a low-diversity brachiopod assemblage only recorded in the southernmost part the Calingasta-Uspallata Basin, whose biostratigraphic relationships with the TivertoniaStreptorhynchus Fauna still needs revision. It is also important to note that brachiopods of the Levipustula levis zone have a relatively coeval postglacial fauna (Aseptella-Tuberculatella/Rhipidomella-Micraphelia). The significant compositional differences identified between both faunas have been explained by a group of abiotic factors directly related to glacial retreat dynamics and the coastal configuration. Age of the brachiopod zones mentioned above is mainly based on the palynological-palaeofloristic information but radiometric data have been also provided for the Levipustula levis zone (319.57±0.09 Ma U-Pb ages dated from the Guandacol Formation) and the Tivertonia jachalensis-Streptorhynchus inaequiornatus zone (312.82±0.11 Ma U-Pb ages from the transgressive marine deposits of the Tupe Formation). In eastcentral Argentina, in the Sauce Grande Basin, brachiopod assemblages integrate the Tomiopsis harringtoni zone herein proposed, restricted to pre-Sakmarian because of the SHRIMP age of 280.8±1.9 Ma from tuff-rich levels in the Tunas Formation. This fauna appears typically associated with the postglacial Eurydesma Fauna also identified in the glacial sequences of the Paraná Basin, Brazil, as the Eurydesma-Lyonia Fauna.Fil: Cisterna, Gabriela Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. 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: Sterren, Andrea Fabiana. 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; ArgentinaXII Congreso de la Asociación Paleontológica ArgentinaCiudad Autónoma de Buenos AiresArgentinaAsociación Paleontológica Argentin