EXHUMATION HISTORY OF THE SIERRA PIE DE PALO UPLIFT AND IMPLICATIONS FOR TECTONIC DRIVERS OF BROKEN FORELAND BASIN EVOLUTION, ARGENTINA

A debate exists over the tectonic driver responsible for inboard exhumation of the Sierras Pampeanas basement-involved uplifts of the Andean foreland of Argentina. Previously published cooling dates from the Sierras Pampeanas have shown complex values ranging from early-Andean cooling (>100-30 Ma) to late-Andean cooling (<10 Ma). Older cooling dates >30 Ma suggest exhumation in the early stages of Andean deformation during a period of normal angle subduction potentially facilitated by the presence of inherited structures. Younger cooling dates <10 Ma suggest shallow angle “flat-slab” and greater plate coupling as the primary driver of foreland deformation. This work aims to provide new geo-/thermochronologic data from the Proterozoic bedrock and flanking basin deposits that may resolve the exhumational history of the Sierra Pie de Palo, the westernmost basement uplift of the Sierras Pampeanas. Apatite (U-Th)/He (He) thermochronometry dates and zircon U-Pb ages are acquired for 6 Proterozoic bedrock samples collected along transects in the southern margins of Sierra Pie de Palo. Preliminary apatite He dates range from 24.7 ± 4.5 to 346.2 ± 19.0 Ma. Bedrock zircon U-Pb ages yield Cambrian-Ordovician metamorphic age constraints for thermal modeling of apatite He data using HeFTy 2.1.5. Detrital zircon U-Pb results from the onlapping foreland basin deposits yield a ~13 Ma maximum depositional age that provide near surface time-temperature constraints. Integrated thermal history modeling and basin analysis will provide new constraints on timing and thus tectonic drivers of exhumation and uplift which has important implications for understanding the proposed structural and kinematic models for the Sierra Pie de Palo uplift.