Lower Cretaceous provenance in the northern Austral basin of Patagonia from sedimentary petrography

•Presentation of four stratigraphic profiles of the first coarse-grained regressive sequence along the northern Austral basin from Patagonia.•Sedimentary petrography as tool to study the tectonic setting during the Lower Cretaceous.•Provenance analysis shows mainly orogen recycled source and subordinated magmatic arc.•Potential surrounding basement sources in agreement with proposed Aptian uplift and exhumation of Patagonia.

The northern Austral basin from Patagonia is characterized by an Early Cretaceous (Barremian–Albian) coarse-grained regressive sequence. These littoral to continental deposits conform a 150 km long basin cropping out along the Southern Patagonian Andes between 47 and 48°S. The basin fill consist of basal deltaic sandstones with interbedded shales and limestones from the Río Belgrano Formation, topped by up to 350 m of fluvial conglomerates and reworked tuffs of the Río Tarde and Kachaike formations. This continental depocenter represent a major geodynamic and paleoenviromental change from the underling marine Río Mayer Formation. In this study we analyze the tectonic setting and provenance during deposition of the coarse-grained sequence using sedimentary petrography of 37 thin sections in four stratigraphic profiles covering the northern basin. Our dataset indicates mainly a recycled orogenic sandstones provenance, in agreement with potential surrounding basement sources.