Dating of the syn-folding Vaca Muerta-Quintuco system based on Sr isotopic ratios of low-Mg shells. New time constraints on an intraplate contractional pulse in the Neuquén basin

Abstract

We present a geochronological and structural study of the sedimentary architecture of the Vaca Muerta-Quintuco System and Mulichinco Formation in Sierra de Reyes and La Yesera anticlines along the Andean front within the Neuquén Basin. Remote sensing mapping coupled with fieldwork has allowed us to analyse an Auquilco-related secondary detachment anticline in the Sierra de Reyes that exhibits growth strata within the Vaca Muerta-Quintuco and Mulichinco formations, with a decrease in growth rate at the top of the uppermost formation. Numerical ages based on ⁸⁷Sr/⁸⁶Sr ratios of calcite shells indicate that anticline growth occurred from Late Jurassic to Early Cretaceous between 148.65 and 132.5 Ma. These ages also allowed us to correlate the Vaca Muerta-Quintuco System in Sierra de Reyes with a published NW-SE seismic transect that traverses the entire Neuquén Basin and extends to the Andean front within the study area. The correlation reveals a coeval period of compression during the growth of the Sierra de Reyes, Loma la Lata and Río Neuquén highs (antiforms), constraining a regional period of intraplate contraction during the latest Jurassic and Early Cretaceous in the Neuquén Basin.