A multiproxy analyses of the Triassic Agua de la Zorra Formation, Cuyana Basin, Argentina: palynofacies, geochemistry, and biotic record

PEDERNERA, TOMÁS; OTTONE, EDUARDO GUILLERMO; MANCUSO, ADRIANA CECILIA; ERRA, GEORGINA; LARRIESTRA, F.; BENAVENTE, CECILIA ANDREA; PINEDA, J.; CAMPOS BARRIOS, CLAUDIO; BUSTOS ESCALONA, EVELYN L.; KRAPOVICKAS, VERÓNICA; MARSICANO, CLAUDIA

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021

0895-9811

The Triassic Agua de la Zorra Formation crops out in the Paramillos de Uspallata area (NW of Mendoza), and represents a deltaic-lacustrine system with volcanic activity as well as episodic incursions of peperitic basalts. The succession includes distal lacustrine facies at base and top, with proximal shallow facies in the middle section. The paleontological record includes invertebrates (spinicaudatans, insects), vertebrates (mainly in the shallow facies), vertebrate tracks and invertebrates traces, and plant remains (mainly referred to Umkomasiales). Kerogen in the distal facies is mostly terrigenous, with scarce amorphous and palynomorphs (disacates and microalgae). It shows a variable percentage of the total organic carbon content (between 0.2 and 4.6), and hydrogen and oxygen indices indicating a type III kerogen. In the shallow facies, kerogen is practically absent, and trace fossils recorded seem to reflect sporadic subaerial exposure of the sediments. The palynological evidence indicates an oligotrophic-mesotrophic? lake. The low productivity recorded was likely caused by fresh lake waters diluted by strong fluvial influence in an overfilled lake basin type. The organic geochemistry data also suggests an overfilled lake basin, and the inorganic geochemistry data support the development of anoxic conditions at the bottom of the paleolake. The spinicaudata valves occur in densely packed beds that could have been driven by changes in the physicochemical parameters caused by the volcanic activity. The volcanic activity in the area is an explanation for subenvironment instability. However, the continuous record of plant remains through out the section indicates that the paleoenvironmental conditions in the surrounding terrestrial areas were more stable than in the paleolake.