Geology of the Devonian black shales of the Appalachian Basin

Geologic Cross Section I–I′ Through the Appalachian Basin from the Eastern Margin of the Illinois Basin, Jefferson County, Kentucky, to the Valley and Ridge Province, Scott County, Virginia

“…Also in the Valley and Ridge province, a complete 2,800-ft-thick section of Middle Devonian to Middle Mississippian strata are present in southeast-dipping beds of the Copper Creek thrust sheet (drill hole 19 and adjoining outcrops). The majority of the westward thinning of the Middle Devonian to Middle Mississippian siliciclastic unit is caused by regional depositional thinning (Roen, 1984;Ettensohn and others, 1988;de Witt and others, 1993).…”

“…The 5,000-to 7,000-ftthick Middle Devonian to Middle Mississippian siliciclastic interval of sandstone, siltstone, and gray shale shown on cross sections C-C′ (Ryder and others, 2012), D-D′ (Ryder and others, 2009), and E-E′ (Ryder, Swezey, and others, 2008) represent the more proximal part of the foreland basin deposits, whereas the 700-to 2,800-ft-thick interval of gray shale, black shale, siltstone, and minor sandstone shown on cross section I-I′ represents the distal sediments that were deposited on the craton beyond the foreland basin (Ettensohn and others, 1988). The black shales are interpreted as anaerobic (anoxic) shallow-marine deposits (Roen, 1984;Ettensohn and others, 1988;Boswell, 1996). According to Ettensohn and others (1988), the subsiding foreland basin may have acted as a "giant sediment sink" that prevented coarser clastic sediment from reaching the distal areas in eastern Kentucky.…”

Characterization of the Marcellus Shale based on computer-assisted correlation of wireline logs in Virginia and West Virginia

“…The range of the measurements is most likely the result of folding and faulting within the Middle to Upper Devonian shale, especially within the Valley and Ridge province (fig. 2); also, Roen (1984) reported the thickness of radioactive black shale in the undivided Skaneateles Shale and Marcellus Shale ( fig. 1), whereas Enomoto (2009) reported the uncorrected wireline log thickness of the Millboro Shale (tables 1, 2).…”

“…The regional thickness of the Marcellus Shale ranges from 0 feet (ft) where it pinches out in east-central Ohio and western West Virginia to as much as 700 ft in southeastern New York (Roen, 1984;Milici and Swezey, 2006;Boyce and Carr, 2009;Ohio Department of Natural Resources, 2010;Smith and Leone, 2010). Within the Broadtop synclinorium (Jacobeen and Kanes, 1974), geologists estimated that the thickness of the Marcellus Shale ranged from 250 to 565 ft Rader and others, 2001;Enomoto, 2009) (fig.…”

“…Map of the study area showing the assessment units from the recent assessment of undiscovered oil and gas resources in the Devonian Marcellus Shale (Coleman and others, 2011;U.S. Geological Survey, 2011), the thickness of radioactive black shale in the undivided Marcellus Shale and Skaneateles Shale (Roen, 1984), and the apparent thickness of the Millboro Shale interpreted from the nine wireline logs included in this study (Enomoto, 2009). Contour lines are in feet (ft).…”