Abstract The Taylorsville basin is a rift basin of Late Triassic to Early Jurassic age in east-central Virginia and adjacent Maryland. The basin has been a target for oil and gas exploration by Texaco and partners in the 1980s, when six continuous cores were drilled followed by three deeper exploratory wells. Currently, no hydrocarbon production has been established from the basin. Relatively thick sequences of dark-colored shale that may serve both as source rocks and self-sourced reservoirs for hydrocarbons have been encountered near the basin’s center. The current USGS assessment concludes that the mean values for undiscovered hydrocarbons in the basin are 1,064 billion cubic feet of gas (BCFG) and 37 million barrels of natural gas liquids (MMBNGL). The Taylorsville basin contains one composite total petroleum system, in which the hydrocarbon potential of the source beds and potential reservoirs were combined and assessed together as a single continuous gas assessment unit. Potential source rocks within the Taylorsville basin include coals and shales of the Triassic Falling Creek and Port Royal formations. Vitrinite reflectance data indicate that the source rocks range from pre-peak oil to peak gas thermal maturity. Potential reservoir rocks are continuous accumulations in shales, coal beds, and tight sandstones as well as possible conventional accumulations in porous and permeable strata within the Triassic Dowell and King George groups. However, well log based sandstone porosity values are generally low. Potential seals may be present in shale beds or igneous intrusions within the basin or by pore-throat restrictions within the continuous reservoir bodies.

Abstract The Late Triassic Taylorsville basin is an onshore continental rift basin along the US Central Atlantic margin. The basin is one member of the early Mesozoic North American rift basin system that trends north–south from the southern US into maritime Canada and has formed within a wide rift zone between Early Triassic collapse of the Appalachian orogen and Jurassic initiation of Atlantic sea floor spreading. The basin, mostly buried under the Cretaceous and younger Atlantic Coastal Plain, is a half-graben having a western border fault. It was a target of conventional exploration drilling >25 years ago, although recent interest is in unconventional gas exploitation. Difference in kerogen type, basement and advective heat flow, and stratigraphic/hydrologic architecture among the Late Triassic–Early Jurassic rift basins is predictable when paleolatitude, paleoclimate, and position within the late Paleozoic Appalachian orogen are considered. For example, the Taylorsville basin, which formed in a humid equatorial climate, is a gasprone overfilled-lake-type basin, in contrast to the temperate oil-prone balanced- to underfilled Newark rift-lake basin. Downhole vitrinite reflectance data and maturation modeling show that the Taylorsville basin, along the axis of Appalachian metamorphism/orogenic collapse, experienced long-term elevated heat flow modified by synrift gravity-driven cross-basin fluid flow (40–55°C/km), compared to the off-axis Newark basin (≤35°C/km). Postrift structural inversion resulted in variable (<1 to >3 km) erosion of Taylorville synrift strata. Duration of sedimentation modeling suggests basin synrift sedimentation likely ended before the Jurassic, unlike sister basins to the north with extant earliest Jurassic formations.