Continental carbonates are rich in palaeoclimatic, palaeoenvironmental and palaeontological information. While carbonate accumulation mechanisms have been described for many types of continental environments, especially in extensional basins, there are still uncertainties that existing facies models fail to address. The Triassic Cerro de las Cabras and Cerro Puntudo formations are alluvial-fluvial-lacustrine sequences that represent a part of the sedimentary infill of two sub-basins of the Cuyana Basin during the early stages of the Triassic rift in west-central Argentina. Previous work has provided absolute dates, confirming that these deposits are coeval (Anisian) allowing a comparative study of carbonate sedimentation in an extensional tectonic context. The description and origin of freshwater carbonate deposits and their surrounding siliciclastic sediments in specific areas of the Cuyana rift, gives insight into the major factors that control carbonate precipitation in all rift basins, including the characterization of the palaeohydrology and the importance of provenance. The Cerro de las Cabras Formation represents an ephemeral, playa-lake depositional system with subaerial exposure and pedogenesis. Its aggradational succession corresponds to the evaporative facies association lake type, diagnostic of underfilled lake basins where persistently closed surface hydrology can lead to thick evaporites. However, this formation lacks thick evaporites and has microbialitic limestones, pointing to an open groundwater supply. The Cerro Puntudo Formation represents an alkaline playa-lake system fed by groundwater and ephemeral surface-water input. The unit is an aggradational-minor progradational succession, pointing to a fluctuating profundal facies association, suggesting a balanced-filled lake type. These two synchronous, lacustrine depositional systems were influenced by tectonics and climate. Provenance and hydrology are key controls in carbonate accumulation in continental rift basins that must be included in future facies models for continental carbonates. Comparison with other rift basins suggests that application of lake-type characterizations coupled with palaeohydrology and provenance patterns will aid in developing new sedimentation models for freshwater limestones in extensional settings.

No abstract

No abstract

No abstract

The Cañadón Asfalto basin, central Chubut, Argentina, comprises a volcano-sedimentary sequence related to the opening of the Atlantic Ocean during Mesozoic times. The Lonco Trapial, Cañadón Asfalto and Cañadón Calcáreo formations are the main units related to the evolution of this basin. The Las Chacritas and Puesto Almada members are distinguished in the Cañadón Asfalto Formation. LA-HR-ICP-MS U-Pb and Lu-Hf data on zircon were obtained on these units. The Lonco Trapial Formation gave a weighted average age of 172.3±1.8 Ma. A pyroclastic level from the Las Chacritas Member gave a weighted average age of 168.2±2.2 Ma. Two U-Pb concordant ages of 160.3±1.7 Ma on a laminated tuffite and 158.3±1.3 Ma on a pyroclastic level were obtained for the Puesto Almada Member. Two maximum depositional ages constrain the sedimentary provenance areas for the basin: 1) A sample from the Sierra de la Manea range, where a

No abstract

No abstract

Las investigaciones interdisciplinarias que han comenzado recientemente en el Macrosistema Iberá buscan, entre otros aspectos, ampliar el conocimiento sobre la arqueología regional. En este artículo se dan a conocer los resultados de los análisis realizados sobre la colección de restos óseos humanos, faunísticos, líticos y cerámicos recuperados en el sitio Isla El Disparito. Sumado a esto se presentan los resultados sedimentológicos, paleobotánicos y mineralógicos del sitio, así como los fechados radiocarbónicos hasta ahora obtenidos. En los trabajos realizados se recuperaron fragmentos cerámicos alisados sin decoración, corrugados y decorados (por incisión y/o impresión), los que corresponderían a variados recipientes de contornos simples o complejos. A esto se suma un variado utillaje confeccionado tanto sobre hueso como sobre material lítico. Este último está elaborado principalmente sobre areniscas, conformado por puntas de proyectil con pedúnculo y aletas rectas o cóncavas; raederas; cuchillos; raspadores, entre otros artefactos. Entre el equipo óseo se cuentan puntas de diversos tipos morfológicos (i.e. convexas, ahuecadas, planas y foliáceas). También se identificaron biseles, un tubo y pendientes. El material faunístico se caracteriza por la elevada frecuencia de mamíferos de pequeño porte, especialmente coipo. Un aspecto particular de este registro es la presencia de Diplodon parallelopipedon, D. charruanus y Castalia sp., bivalvos dulceacuícolas que hasta hace poco tiempo se creía que no habitaban actualmente esta zona. El análisis bioarqueológico permitió identificar un número mínimo de 18 individuos; los mismos presentan rasgos morfológicos dentales coronales propios de poblaciones amerindias. Respecto de la asociación temporal del conjunto recuperado, para el único enterratorio primario identificado se obtuvo una antigüedad 14C de ca. 960 AP. A partir de esta primera cronología y de la caracterización realizada se puede comenzar a abordar el poblamiento y dinámica prehispánica del sector a la luz de nuevos modelos y discusiones actuales.