Fluvial deposits of the Diamante Formation as a record of the Late Cretaceous tectonic activity in the Southern Central Andes, Mendoza, Argentina

GOMEZ, RICARDO; TUNIK, M.; CASADÍO, S.

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Lugar: Santiago de Chile; Año: 2020

0718-7092

The Upper Cretaceous nonmarine deposits of the Neuquén Basin have an importantregional exposure. These deposits are included in the Neuquén Group, a well-studied unitin both the south and central part of the basin. However, the northernmost exposed betweenthe Laguna del Diamante and the Atuel River - assigned to the Diamante Formation - havenot been studied in detail. In the studied area, the Diamante Formation corresponds to abraided fluvial system with moderate sinuosity evolving through time towards ananastomosing fluvial system. Petrographic analyses indicate that sandstones belong tofeldspatic litharenites and litharenites, while the source area indicates provenance from botha recycled orogen and a transitional arc. The latter could be linked to the exhumation of theAndean orogen located to the west and to the input from the north-eastern border of theNeuquén Basin, represented by the rocks currently exposed in the San Rafael Block. On amacroscopic scale, the presence of calcareous lithic fragments in the mid and upper part of the surveyed stratigraphic section, strongly suggest an input from the west. This indicatesan important change in the polarity of the basin and the presence of a deformation frontlocated to the west of the study area in accordance to previous proposals in equivalentdeposits to the south of study area.