POST-OROGENIC THERMAL HISTORY AND EXHUMATION OF THE NORTHERN APPALACHIAN BASIN CONSTRAINED THROUGH LOW-TEMPERATURE THERMOCHRONOLOGY

The Appalachian Basin is a composite, retroarc foreland basin that extends from Southern Quebec (CAN) to northern Alabama (USA). The Northern Appalachian Basin, located predominantly in the states of Pennsylvania (PA) and New York (NY), contains a well-preserved sedimentary record and important reserves of gas in units such as the Marcellus Shale. Our goal is to constrain the post-orogenic thermal and exhumation history of the Northern Appalachian Basin through applying low-temperature apatite fission track (AFT) thermochronology. We sampled Devonian sandstones (stratigraphically close to the Marcellus Shale) along an approximate east-west transect straddling the NY-PA border. Kimberlitic dikes (intruded ~150 Ma) from central NY were also targeted to constrain the post ~150 Ma cooling history and basin exhumation as their thermal history is not affected by hinterland exhumation and post-burial annealing. AFT results from the Devonian sandstones and kimberlitic dikes (in progress) combined with inverse modeling will generate best-fit time-temperature envelopes to constrain the post-orogenic thermal history and the correlative tectonic events. Also, numeric modeling should reveal where conditions were ideal for hydrocarbon generation (e.g., timing/duration of maximum paleotemperatures). Inverse model inputs include AFT age and track length, apatite composition proxies, depositional age of the sampled unit, and data from existing thermal maturation indicators (conodont alteration index and vitrinite reflectance). Previous thermochronology studies, thermal maturation indicators and basin geometry indicates that sediments have likely exceeded temperatures for optimum hydrocarbon generation on the eastern flank of the basin. Therefore, post-deposition AFT ages were likely fully reset in the east, which will potentially be the best data to constrain the post-orogenic thermal/exhumation record and related tectonic events. In the west, fission tracks are likely minimally annealed post-deposition and temperatures remained too low for optimal hydrocarbon generation. Conversely, the center of the basin should contain partially annealed tracks due to long-residence within the partial annealing zone, which significantly overlaps the hydrocarbon generation window.