Post-orogenic thermal history and exhumation of the northern Appalachian Basin: Low-temperature thermochronologic constraints

Apatite fission-track (AFT) thermochronology and (U-Th)/He (AHe) dating, combined with paleothermometers and independent geologic constraints, are used to model the thermal history of Devonian Catskill delta wedge strata. The timing and rates of cooling determines the likely post-orogenic exhumation history of the northern Appalachian Foreland Basin (NAB) in New York and Pennsylvania. AFT ages generally young from west to east, decreasing from ~185 to 120 Ma. AHe single-grain ages range from ~188 to 116 Ma. Models show that this part of the Appalachian foreland basin experienced a non-uniform, multi-stage cooling history. Cooling rates vary over time, ~1–2 °C/Myr in the Early Jurassic to Early Cretaceous, ~0.15–0.25 °C/Myr from the Early Cretaceous to Late Cenozoic, and ~1–2 °C/Myr beginning in the Miocene. Our results from the Mesozoic are broadly consistent with earlier studies, but with the integration of multiple thermochronometers and multi-kinetic annealing algorithms in newer inverse thermal modeling programs, we constrain a Late Cenozoic increase in cooling which had been previously enigmatic in eastern U.S. low-temperature thermochronology datasets. Multi-stage cooling and exhumation of the NAB is driven by post-orogenic basin inversion and catchment drainage reorganization, in response to changes in base level due to rifting, plus isostatic and dynamic topographic processes modified by flexure over the long (~200 Myr) post-orogenic period. This study compliments other regional exhumation data-sets, while constraining the timing of post-orogenic cooling and exhumation in the NAB and contributing important insights on the post-orogenic development and inversion of foreland basins along passive margins.