Abstract The Richmond basin, a rift basin of Late Triassic to Early Jurassic age in east-central Virginia, produced the first coal mined in the United States in the early 1700s. These Triassic coal beds are thick and gas-rich, and fatal explosions were common during the early history of exploitation. Since 1897, at least 38 confirmed oil, natural gas, and coal tests have been drilled within the basin. Although shows of asphaltic petroleum and natural gas indicate that active petroleum systems existed therein, no economic hydrocarbon accumulations have been discovered to-date. The Richmond basin has been assessed by the U. S. Geological Survey (USGS) as one composite total petroleum system, in which the hydrocarbon potential of the source beds (both coal and dark shale) and potential reservoirs have been combined into a single continuous tight gas assessment unit within the Chesterfield and Tuckahoe groups (Upper Triassic). Sandstone porosities are generally low (<1 % to 14 %). Thick, dark-colored shales have total organic carbon (TOC) values that range from <1% to 10%, and vitrinite reflectance (%R O ) values that range generally from about 0.3 to 1.1%, which indicates that the submature to super mature shales appear to be the source of the hydrocarbons recovered from some of the boreholes. The stratigraphic combination of these potential source rocks, tight sandstones, and hydrocarbon shows are the basis for the current USGS assessment of the technically recoverable undiscovered hydrocarbon resources of the basin. Mean values for these resources are 211 billion cubic feet of gas (BCFG) and 11 million barrels of natural gas liquids (MMBNGL).

Abstract Sedimentary basins in the eastern United States (U.S.) contain strata ranging in age from Neoproterozoic to Holocene and have been the source of petroleum and coal that fueled much of the initial growth and development of the U.S. as a major industrial power. It is estimated that at least 87 billion barrels of oil (BBO) and natural gas liquids (BBNGL) and 664 trillion cubic feet of natural gas (TCFG) have been produced to-date from these basins. These basins developed on continental and transitional oceanic-continental crust ranging in age from the Paleoproterozoic to Triassic. Many of these basins have undergone structural readjustment and uplift, some being nearly completely inverted. The oldest of these basins considered here are Mesoproterozoic to Early Cambrian in age. They include the Midcontinent rift, Reelfoot rift, Rough Creek graben, and Rome trough. These basins are dominantly rift basins, which formed within the North American craton, presumably as a result of plate tectonic forces associated with the rifting of the Rodina supercontinent and the opening of the Iapetus Ocean. Petroleum systems have been identified or postulated in these four basins. Overlying these basins are the three large Paleozoic-aged sag-foreland basins of the eastern U.S.: the Michigan, Illinois, and Appalachian basins. Additionally included are the eastern extent of the Arkoma-Ouachita-Black Warrior foreland basin and a relict Gondwanan basin that was left behind in present-day north Florida following the Mesozoic rifting of Pangea. A mixed siliciclastic–carbonate–evaporite sedimentary section includes reservoirs and seal facies for many play types. Multiple petroleum systems have been identified or postulated in all of these basins. Succeeding these large Paleozoic sag and foreland basins are the Late Permian(?) to Early Jurassic rift basins that rim the eastern continental margin of the U.S. These basins have formed as a result of plate tectonic forces associated with the opening of the Atlantic Ocean and the Gulf of Mexico. Basin-fill sequences are generally lacustrine and continental-playa siliciclastic strata containing locally significant coals and minor carbonates. Petroleum systems have been identified or postulated in several of these basins, including the Dan River-Danville, Deep River, Newark, Richmond, and Taylorsville basins. Finally, overlying this complex stack of Proterozoic, Paleozoic, and early Mesozoic basins are the great Gulf of Mexico and Atlantic margin basins. The Gulf of Mexico Basin is distinguished by the dominating structural control of the salt and shale tectonics on a mobile substrate, whereas the basins of the western Atlantic margin are associated mainly with faulting associated with the opening of the Atlantic Ocean. Only the Carolina Trough of the western Atlantic margin basins has mobile salt structures. The sedimentary sequences of both basins are a mixed siliciclastic–carbonate interval containing coal and lignite in variable quantities in the updip portions of the basins. A composite total petroleum system has been identified in the Gulf of Mexico basin that incorporates several Mesozoic and Cenozoic petroleum source rocks with many reservoir rocks and seals throughout the sedimentary sequence. A combination of cultural and tectonic setting, sediment provenance and delivery systems, and paleo-oceanographic conditions have made the Gulf of Mexico basin one of the most prolific petroleum provinces on the planet. The current understanding of the Atlantic margin basin suggests that it does not appear to have a similar accumulation of petroleum resources as the Gulf of Mexico Basin. Correlated and potential petroleum source rock intervals have been penetrated in several of the offshore post-rift Atlantic margin subbasins; however, in many places on the shallow shelf, these intervals are generally too organically lean and (or) too immature to be major source rocks. A single petroleum system has been locally demonstrated in the offshore Atlantic by a non-commercial gas-condensate discovery. Additional petroleum systems in the western Atlantic may be identified as research continues. Source rock intervals penetrated by Deep Sea Drilling Project and Ocean Drilling Program cruises farther off-shore have generative potential, but data from these projects are too sparse to identify petroleum systems connecting these source rocks with potential reservoir targets.

Orbitally controlled, sedimentary cycles of the Newark Supergroup permit palyniferous Late Triassic sections to be calibrated in time. Carnian palynofloras from the Richmond basin exhibit 2-m.y. fluctuations in the spore/pollen ratio, but taxonomic composition remains stable. Diversity of Norian and Rhaetian palynofloras increases prior to a 60% reduction at the Triassic/Jurassic boundary. The extinction of Late Triassic palynomorph species is coincident with a spike in the spore/pollen ratio and approximately synchronous with the last appearances of tetrapod taxa and ichnofossil genera. This geologically brief episode of biotic turnover is consistent with bolide impact hypotheses.