TAPHOFACIES AND BIOFACIES OF THE VACA MUERTA FORMATION IN THE SOUTHERN MENDOZA SECTOR OF THE NEUQUEN BASIN: PALEOECOLOGICAL, SEDIMENTOLOGICAL AND STRATIGRAPHIC IMPLICATIONS

摘要

TAPHOFACIES AND BIOFACIES OF THE VACA MUERTA FORMATION IN THE SOUTHERN MENDOZA SECTOR OF THE NEUQUEN BASIN: PALEOECOLOGICAL, SEDIMENTOLOGICAL AND STRATIGRAPHIC IMPLICATIONS. Taphonomic and paleocological studies of fossil assemblages from the transgressive and highstand succession of the Vaca Muerta Formation (lower Tithonian to upper Valanginian) in Loncoche Creek, Rahue Creek and Cuesta del Chihuido, Mendoza province, was carried out. A range of paleoenvironments that include mid, outer and basin deposits of carbonate ramp have been determinated based on integrated studies of taphofacies, biofacies, lithofacies and microfacies. In the mid ramp zone were recognized the following taphofacies: two types of autoparabiostromes, as well as concentrations of bivalves, gastropods and serpulids. Meanwhile, biofacies included autobiostromes rich in grypheids and serpulids. In the outer ramp zone were recognized two types of parabiostromes, ammonite and aptychus pavements, bioclastic detritus, molluscs and brachiopods pavements, besides bioturbated nodular limestones and truncated ammonites. In this zone, biofacies are characterized by high diversity including: Lingularia-Discinisca, infaunal bivalves, epistominid foraminifers, filament bivalves, besides of pectinidae, oysters and inoceramid bivalves, hardgrounds and microbial mats. Taphofacies and biofacies data allow to estimate relative sea level changes, sedimentation rates, substrate consistency, oxygenation, nutrient levels and productivity.