Freshwater bivalves and their environmental conditions in a Jurassic lacustrine system (Cañadón Asfalto Formation) from Patagonia, Argentina

MONFERRAN, M.D.; CABALERI, N.G.; ARMELLA, C.; MARTÍNEZ, S.; GALLEGO, O.F.; ZACARÍAS, I.A.; BARRIOS CALATHAKI, H.

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Lugar: Santiago de Chile; Año: 2023

0718-7092

At the moment, two freshwaterbivalve species were described for the continental Jurassic of Patagonia: Diplodon simplex Morton and Diplodon matildensis Morton from LaMatilde Formation of the Santa Cruz province. The Cañadón Asfalto Formationlocated in Chubut province exhibits a high diverse invertebrate fossil fauna preservedmainly in lacustrine facies, which includes clam shrimps, bivalves, gastropods,ostracods and insects. However, few studies have been carried out on freshwaterbivalve of this geological unit. In this work, a morphological description ofbivalve assemblage and paleoenvironment analysis from the Cañadón AsfaltoFormation was performed. Forty samples were collected from three stratigraphic levelsat the Cañadón Asfalto locality. Theselevels are ash fall tuffs rich in glass particles accumulated in a lacustrine system withdevelopment of microbial activity. Morphological analyzes of outline and sizes wereperformed at each level.. Our results showing the smallest-sized association ofunionids recorded for the Jurassic time with size ranging from 7.6–11.7 mm longand 5.2–7.6 mm high. Theenvironmental influence of pyroclastic falls could have played an importantrole in the development of the sizes of populations and shells.