PALYNOLOGY, PALYNOFACIES AND GEOCHEMISTRY ON THE TRIASSIC CASA PIEDRA FORMATION, RINCÓN BLANCO GROUP, ARGENTINE PRECORDILLERA: DEPOSITIONAL ENVIRONMENT AND HYDROCARBON POTENTIAL

Abstract

This paper presents the study of the kerogen recovered from the Casa de Piedra Formation. The analysis includes systematic palynology, palynofacies, organic geochemistry (total organic carbon – TOC – and pyrolysis Rock-Eval) and inorganic geochemistry (X-ray fluoroescence). A new spore species is introduced: Rugulatisporites claudiae sp. nov. Three palynofacies are defined throughout the unit. The uppermost horizons, P1, fluvial in origin, include low TOC contents, a kerogen Type III, mostly terrigenous-derived, and a relatively diverse miospore assemblage largely dominated by disaccate pollen grains of umkomasiaceous/ peltasperm affinity; the K/Rb ratio is high, V is scarce, and Mo is absent. The middle, lacustrine section, P2, includes relatively high TOC values, a mostly amorphous rich kerogen Type II, and abundant Botryococcus sp.; the K/Rb ratio is relatively low, V is high, and Mo is present. The kerogen at the basalmost horizon, P3, is similar to the uppermost section, but includes relatively high percentages of amorphous organic matter and Botryococcus sp.; the K/Rb ratio is the lowest of the section, V is relatively low, and Mo is absent. The kerogen from the lacustrine P2 exhibits a moderate hydrocarbon genetic potential (ca. 3 to 31 kg HC/ ton). doi: 10.5710/AMGH.31.05.2019.3247