APATITE (U-TH-SM)/HE THERMOCHRONOLOGY AND THERMAL HISTORY MODELING OF THE CATSKILL-POCONO SILICICLASTIC WEDGE, ACADIAN BASIN (CENTRAL PENNSYLVANIA)

Mountain building during the Acadian orogeny (eastern USA) led to flexural subsidence and siliciclastic infilling of the Acadian foreland basin, an important archive of tectonic and environmental conditions along eastern Laurentia. We present detrital apatite (U-Th-Sm)/He thermochronology data from the Devonian–Mississippian Catskill-Pocono siliciclastic wedge to quantify the youngest resolvable low-temperature history of basin burial heating, uplift, and exhumation. We collected six sandstone samples from Devonian–Mississippian marine and fluvial deposits exposed in the Port Matilda section (Pennsylvania, USA) of the Catskill-Pocono wedge for detrital provenance analysis and apatite, zircon, and monazite geo-thermochronology. Here we report new apatite (U-Th-Sm)/He dates (n=30), which are sensitive to burial heating and cooling towards the surface through closure temperatures of ~40–80 ºC and corresponding ~2–3 km closure depths. Thermal history modeling of apatite He data provides constraints on the lowest temperature history of the basin and a foundation for interpreting higher-temperature thermochronometers. Based on published vitrinite reflectance data, we predict partial to complete thermal resetting of the apatite He system. Incomplete resetting may preserve evidence of burial heating history, as indicated by down-section younging of apatite He dates that post-date depositional age. Alternatively, invariant and young dates within the stratigraphic succession may indicate complete resetting followed by rapid or protracted basin inversion, cooling, and exhumation. In either scenario, apatite He dates provide an upper bound on the most recent basin cooling and fill a geographic gap in existing low-temperature thermochronology across the central Appalachian mountains. North of our study area, detrital apatite fission track and (U-Th)/He thermochronology data depict an eastward younging, multi-stage cooling history of the Catskill-Pocono wedge since Early Jurassic time. Our apatite results will be integrated with higher-temperature monazite and zircon thermochronology and thermal history modeling to evaluate provenance, sediment recycling, and complex basin burial histories during orogenesis and post-orogenic exhumation.