RESOLVING ALONG-STRIKE ANDEAN THRUST FRONT EVOLUTION USING THE FORELAND BASIN RECORD IN THE FLAT SLAB REGION OF ARGENTINA

The Neogene Bermejo Basin of west-central Argentina is a classic example of a broken foreland basin system characterized by basement-involved uplifts of the Sierras Pampeanas and thin skinned Central Precordillera fold-thrust belt partitioning the once continuous foreland basin. However, the kinematic relationship between the Sierras Pampeanas, the Central Precordillera, and the enigmatic west-vergent Eastern Precordillera thrust front remains debated. End member tectonic models for Eastern Precordillera deformation include: (1) thin-skinned deformation at 8-6 Ma associated with the Central Precordillera fold-thrust belt to the west, and (2) thick-skinned deformation at <5 Ma linked to Sierras Pampeanas deformation to the east. Our study seeks to constrain the along-strike Neogene tectonics for the Eastern Precordillera by integrating new structural geology, stratigraphic, detrital zircon U-Pb geochronology provenance, and detrital apatite low temperature thermochronology datasets from the Bermejo Basin. New data from a ~1.8 km thick Neogene stratigraphic section in southern Bermejo Basin constrains deposition between ~13-5 Ma with dominant fluvial-lacustrine mudstones, siltstones and sandstones, that transition into fluvial/alluvial fan conglomerate facies around 7 Ma. New detrital apatite thermochronology ages from the base of the measured section record mean age of ~7 Ma, suggesting a kinematic linkage to thin-skinned deformation in the Central Precordillera. When we compare our new data with published data from northern Bermejo Basin, we observe a north to south: (1) decrease in stratigraphic thicknesses, and (2) increase in exhumation ages along strike. To further investigate these along-strike variations, we will measure additional stratigraphic sections in southern Bermejo Basin coupled with detailed mapping and sample collection for geo-thermochronology analyses.