U-PB geochronology and magnetostratigraphy of a north Patagonian syn-orogenic Miocene succession: Tectono-stratigraphic implications for the foreland system configuration

Abstract

The syn-orogenic Miocene deposits of the Patagonian Foreland System were the focus of numerous works in the latest years, due to their central role in the comprehension of the tectono-stratigraphy and tectonic evolution related to the Patagonian Andean growth. In this work we present a chronostratigraphic scheme based on magnetostratigraphy and U[sbnd]Pb geochronology for one of the syn-orogenic successions of the Patagonian Foreland System: the Paso del Sapo Basin. The sequence is constrained to an age of >14.9 to <11.6 Ma, establishing ages of >14.9–14.6 Ma for the basal alluvial systems of La Pava Formation, with mean sedimentation rates of 4.2 cm/kyr; of 14.6 to 12.8–12.7 Ma for the lacustrine - deltaic environments of the lower Collón Cura Formation, with sedimentation rates ranging from 1.6 to 26.0 cm/kyr; and of 12.8–12.7 to <11.6 Ma for the alluvial systems of the upper Collón Cura Formation, with mean sedimentation rates of 8.5 cm/kyr. Our results indicate a continuous contractional tectonic phase at least during this time span (>14.9 to <11.6 Ma), which implicates that the Patagonian Foreland System at these latitudes was synchronously deformed with the tectonic activity along the Andean region.