INSTITUTO DE GEOCRONOLOGIA Y GEOLOGIA ISOTOPICA
Unidad Ejecutora - UE
congresos y reuniones científicas
13C, 18O and 87Sr/86Sr of Early Callovian Limestones from Cuenca Neuquina, Argentina.
CAGNONI, M. C.; RAMOS, A. M.; VALENCIO, S. A.; PANARELLO, H.O.; ARMELLA, C.; CABALERI, N. G.
Punta del Este
Congreso; V Sud American Symposium on Isotope Geology; 2006
Facultad de Agronomía - Facultad de Ciencias, Univesidad de la República
ABSTRACT 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. δ13C and δ18O 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. δ13C 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 δ13C 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.