CONTRASTING CLIMATE-RELATED STRATIGRAPHIC ARCHITECTURE AND ITS INFLUENCE ON BASIN-SCALE SYN-RIFT ADVECTIVE FLUID FLOW, NEWARK AND TAYLORSVILLE BASINS

The system of Early Mesozoic Newark Supergroup rift basins runs from Georgia to Nova Scotia and covers 16 degrees of modern and paleo-latitude. Recent borehole and surface vitrinite reflectance data, recording paleomaximum temperatures in the Taylorsville (VA) and Newark (NY/NJ/PA) basins, show patterns of syn- to early post-rift advective fluid flow. These data indicate the syn-rift redistribution of heat by intrabasin steady state advective processes is dependent on basin hydrostratigraphy whose architecture is a combined result of tectonic changes of basin accommodation with time and the latitudinal climatic influence on fluvio-lacustrine clastic sedimentation, with the latter climatic effect producing major interbasin differences in advective heat flow patterns.

Taylorsville basin data shows that syn-rift geothermal gradients were lower (40 C/km) in the western basin up to 20 km from the western border fault than in the eastern basin (50- 55 C/km). This is attributed to a ground water flow system driven by border fault relief, and facilitated by abundant coarse fluvial facies throughout the stratigraphy that extend significantly into the basin: the basin formed under paleoequatorial humid conditions in which thick coarse alluvial fans and fan deltas prograded far into the basin during lake highstands.

In the more arid Newark basin, less permeable lacustrine mudstones dominate strata above the basal fluvial Stockton Fm. In post- Stockton formations, coarse facies at the border fault and heat flow depression from meteoric downwelling did not extend far (<5 km) into the basin. The geothermal gradient in post-Stockton formations increased from ~25 C/km to ~35 C/km by the end of syn-rift sedimentation due to heating of downwelling meteoric water at the basin floor adjacent to the border fault and subsequent cross-basin steady state heated fluid flow through the Stockton confined lateral aquifer.

The lower background regional geotherm (~25 C/km) of the Newark basin is due to position off the axis of Late Paleozoic Alleghanian metamorphism and subsequent post-orogenic collapse, while the on-axis Taylorsville basin had a higher long term basement heat flow (~45 C/km). Post-rift (185-175 Ma) structural inversion produced transient advective heat flow anomalies and cooling of basin-scale ground water systems.