INVESTIGADORES
CABALERI nora Graciela
congresos y reuniones científicas
Título:
Facies and carbon/oxygen isotopes of the Calabozo Formation, arroyo La Vaina, Mendoza, Argentina.
Autor/es:
CABALERI, NORA; VALENCIO, SUSANA; CAGNONI, MARIANA; RAMOS, ADRIANA; ARMELLA, CLAUDIA; PANARELLO, HÉCTOR; RICCARDI, ALBERTO
Lugar:
Pucón, Chile
Reunión:
Simposio; III South America Symposium on Isotope Geology; 2001
Institución organizadora:
Seervicio geológico Minero de Chile
Resumen:
Facial / microfacial studies and geochemicalisotopicanalyses on marine jurassic carbonates of theCalabozo  were carried out to reconstruct the palaeoenvironment and postdepositionalhistory of the unit. This study is part of a project which purpose is the sedimentological andgeochemical characterization of the Jurassic carbonate sequences of Cuenca Neuquina, in thesouthwestern Mendoza, Argentina. A good agreement between the facial/microfacialand the chemical and isotopic data is observed in the reconstruction of the palaeoenvironment during deposition of the carbonatic succession of Calabozo Formation, at arroyo El Plomo.Although these carbonates undergone more than a postdepositional process, petrographic and geochemical determinations indicate that they did not highly affected these rocks. Oxygen isotope system, the most sensitive indicator of diagenesis, show O-18 compositions quite depleted, indicating they are obliterated by later postdepositional events. Despite of this, δ18O still maintain a variation pattern that reflects the environmental conditions prevailing during deposition. A shift to enriched values is observed towards the upper levels of each shallowing-upward cycle,  indicating the establishment of more intense evaporative conditions and the progressive restriction in the water circulation, with the consequent loss of 16O. On the other hand, carbon isotope system retained best the primary isotopic characteristics. Limestones deposited in the deepest areas of the basin (lower cycle), are the best preserved and their 13C signature is in concordance with the Callovian unaltered marine carbonates. A grow to isotopically lighter carbon is observed through the shallowing-upward levels of the middle and upper cycles, remarking the input of organically derived carbon and episodes of subaereal exposure.A good agreement between the facial/microfacial and the chemical and isotopicdata is observed in the reconstruction of thepalaeoenvironment during deposition of the carbonatic succession of Calabozo Formation, at arroyo El Plomo. Although these carbonates undergone more than a postdepositional process, petrographic and geochemical determinations indicate that they did not highly affected these rocks. Oxygen isotope system, the most sensitive indicator of diagenesis, show O-18 compositions quite depleted, indicating they are obliterated by later postdepositionalevents. Despite of this, δ18O still maintain a variation pattern that reflects the environmentalconditions prevailing during deposition. A shift to enriched values is observed towards the upper levels of each shallowing-upward cycle, indicating the establishment of more intense evaporative conditions and the progressive restriction in the water circulation, with the consequent loss of 16O. On the other hand, carbon isotope system retained best the primary isotopiccharacteristics. Limestones deposited in the deepest areas of the basin (lower cycle), are the best preserved and their 13C signature is in concordance with the Callovian unaltered marine carbonates. A grow to isotopically lighter carbon is observed through the shallowing-upwardlevels of the middle and upper cycles, remarking the input of organically derived carbon and episodes of subaereal exposure.