CONTRASTING THERMAL EVOLUTION OF THE NEWARK AND TAYLORSVILLE BASINS: INHERITED ALLEGHANIAN HEAT FLOW AND CLIMATE-INFLUENCED HYDROSTRATIGRAPHY

The system of Early Mesozoic Newark Supergroup rift basins runs from Georgia to Nova Scotia and covers 16 degrees of modern and paleo-latitude. They make up a wide rift system, overprinting the late Paleozoic Alleghanian orogen, and were one phase in the collapse of that orogen: succeeding early post-orogenic ductile exhumation and preceding initiation of Atlantic seafloor spreading.

The contrasting syn- to early post-rift thermal evolution of the Newark (NY/NJ/PA) and Taylorsville (VA) basins, based on recent borehole and surface vitrinite reflectance measurements combined with published cooling data, indicate material differences in basement heat flow and basin hydrostratigraphy. Basal basin heat flow is a relict of position relative to the Alleghanian orogenic metamorphic/ thermal axis, which was also the locus of post-orogenic collapse. The Taylorsville basin is located on the metamorphic axis and had a background geotherm of ~45?C/km, modified by a syn-rift gravity-driven groundwater system producing crossbasinal variation in geothermal gradient (40-55?C/km). The Newark basin, west of the metamorphic axis, had a background gradient of ~25?C/km. Syn-rift steady state heated groundwater flow through basal basin fluvial strata conductively heated overlying formations to ~35?C/km. The interbasin differences in advective heat flow patterns are due to latitudinal climate influence on basin syn-rift coarse sedimentation and resulting hydrostratigraphic architecture.

Change in stress regime due to post-rift structural inversion (~180 Ma) produced transient advective events and exhumation that both cooled the basin-scale groundwater systems and variably eroded 0.4-3.1 km from the Taylorsville basin and >6 km from parts of the Newark basin.