Tidally dominated ramp facies at the Picún Leufú Formation (Jurassic/Cretaceous boundary) in southern Neuquén basin, Argentina

ARMELLA, CLAUDIA; CABALERI, NORA G.; LEANZA, HÉCTOR A.

CRETACEOUS RESEARCH (PRINT)

Elsevier

Lugar: Amsterdan; Año: 2007 vol. 28 p. 961 - 979

0195-6671

A paleoenvironmental model for the Picún Leufú Formation (Jurassic/Cretaceous boundary) cropping out in the Neuquén basin (Argentina) at the southwestern margin of Gondwanaland, is presented in this paper for the first time. Detailed stratigraphic sections exposed at the national road nº 40 where it crosses the Picún Leufú creek (type locality) and in the Cerrito Caracoles area, were examined and sampled. Based on the combination of the obtained sedimentological data (facies/microfacies analysis) and the relationship between benthic macrofaunas and their taphonomic attributes, it is concluded that the Picún Leufú Formation, represents a tidally dominated rimmed shelf setting characterized by prograding bars dissected by channels and thick lagoonal facies with shoal developments. In the Cerrito Caracoles area, where only its basal part is exposed, the Picún Leufú Formation seems to have been deposited in a somewhat shallow subtidal marine environment, where associations of shelf margin with developments of patch reefs have been recognized.