Along Strike Tectonic Evolution of the Neogene Bermejo Foreland Basin and Eastern Precordillera Thrust Front, Argentina (30-32ºs)

The Bermejo retroarc foreland basin system formed in flexural response to Miocene crustal thickening in the Andean orogenic system, specifically, the eastward propagation of the Precordillera fold-thrust belt and the basement-involved uplift of the Sierras Pampeanas. Previous work in the area has mainly focused on the mechanisms and expression of flat slab subduction and the structural geometry of the basement-involved Sierras Pampeanas and east-vergent Precordillera fold-thrust belt at depth. Much of this work has furthered the understanding of Bermejo basin evolution north of 31ºS, however debate still exists whether the N-S trending Bermejo basin evolved synchronously or asynchronously through time. An in-depth, along-strike analysis of the Bermejo basin is required to determine whether or not the basin evolved synchronously. Our study seeks to constrain the along-strike Neogene tectonics of the Eastern Precordillera via well exposed Bermejo basin deposits through integration of new stratigraphic, detrital zircon U-Pb geochronology provenance, and detrital apatite low temperature thermochronology datasets from southern Bermejo basin. New data from twomudstones, siltstones and sandstones that transition into fluvial-alluvial fan conglomerate facies tracking the eastward migration of deformation. New detrital apatite thermochronology ages from the base of the measured sections record a mean age of ca. 6 Ma, suggesting two temporally distinct deformation events along-strike of the Bermejo basin. When we compare our new data with published data from northern Bermejo, we observe a north to south: (1) decrease in stratigraphic thicknesses, and (2) increase in exhumation ages along strike. This study utilizes newly collected data in comparison with published data to constrain along-strike variability of Precordillera thrust-front evolution and Bermejo basin development