A new Early Jurassic marine locality from southwestern Chubut Basin, Argentina

S.MARIEL.FERRARI; SANTIAGO BESSONE.

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Lugar: Santiago de Chile; Año: 2015 vol. 42 p. 349 - 363

0718-7092

A shallow marine invertebrate association is reported from a new Early Jurassic locality namely La Casilda,which is situated in the southwestern region of the Chubut Basin (Patagonia, Argentina). The marine deposits of La Casildaare located in the Río Genoa valley and bear a diverse invertebrate fauna including bivalves, gastropods, brachiopods,echinoderms and corals. A preliminary taxonomic analysis of the invertebrate fauna suggests that La Casilda depositsbelong to the Mulanguiñeu Formation of late Pliensbachian-early Toarcian age, and may be coeval with those from themarine localities previously sampled in other regions of the Río Genoa valley. The preliminary results of a biodiversityanalysis displayed that La Casilda is one of the most diverse localities at the Chubut Basin and could be assigned to thebiofacies at the mixed siliciclastic-carbonate ramp proposed for the marine Early Jurassic at the Andean Basin of northernChile. The evolution of the marine transgression during the early Pliensbachian-early Toarcian is also interpreted herein a time scale based on ammonite faunas, giving a preliminary temporal reconstruction of the entire Chubut Basin.