CONICET | Buscador de Institutos y Recursos Humanos

We studied the palaeoenvironments of Callovian carbonate ramp of the Calabozo Formation along a meridional stripe from the Arroyo Serrucho to Río Potimalal (Cuenca Neuquina, SW Mendoza province). The subenvironments correspond to inner, middle, outer and marginal ramp facies. The progressive isolation of the basin originated evaporative conditions corresponding to Tábanos Formation. Good correlation between sedimentology, isotopic and trace elements was observed in the reconstruction of the depositional conditions of the Calabozo Formation limestones. Delta13C and Delta18O values suggest diagenetic overprint and other superposed processes. Oxygen isotope system is the most sensitive and shows 18O compositions quite depleted that also reflect the changes in local palaeoenvironmental conditions related to palaeoclima, sea level fluctuations, meteoric ground waters interaction and freshwater contribution. Carbon isotope system has best retained the primary isotopic characteristics. Delta13C values (0 to 3.9) are near the Callovian marine carbonates values (≈0.5 to 4). A maximum around 3.5 - 3.9 is recorded in the storm facies from the top of Arroyo Serrucho section. These 13C compositions could be originated by seawater high primary organic productivity and local water inputs with inorganic carbon strongly enriched during the establishment of the shallow marine environment of the carbonatic ramp. The lower levels of this section, with Delta13C values around 0.1, are in transition with Lajas Formation and they could reflect dysoxic water conditions. 87Sr/86Sr ratios of the best preserved carbonates of Arroyo El Plomo, Arroyo La Vaina and Río Potimalal sections are in agreement with the Callovian seawater Sr-isotope curve. This is the INGEIS Contribution Nº 285. This study was founded by CONICET (Grant PIP 4517/97) and ANPCyT (Grant PICT 07-12128).