Facies interpretation and regional stratigraphic study of the Upper Devonian Gordon zone and associated beds in northern West Virginia and southwestern Pennsylvania

Subsurface correlation of 250 well logs and isopach mapping of Upper Devonian beds across western Pennsylvania and northern West Virginia have been coupled with a core study in Washington County, Pennsylvania, to determine the nature and distribution of the Upper Devonian Gordon zone. The complete stratigraphic section studied includes the Fifth, Fourth, Gordon, Gordon Stray, Thirty Foot, Fifty Foot, and Gantz beds. Along with isopach maps, net sandstone maps were generated for improved characterization of sandstone geometry and facies distribution across the field area. Cross-sections including four west to east and one north to south were constructed to aid in stratigraphic analysis. The resultant sediment distribution patterns with the developing Late Famennian foreland basin were dominantly barrier bar and delta front environments. The evaluation of net sandstone geometries suggests that these depositional systems were influenced by a combination of structural features related to the Rome Trough graben fault system, and eustatic fluctuations. Two major fault boundaries along the length of the Rome Trough in western Pennsylvania and northern West Virginia influenced deposition and position of the shorelines in the late Famennian by creating continuous accommodation space. This resulted in the stacking of shoreline sandstone across the field area. In addition, isopach maps and cross-sections show that the Gordon Stray shorelines jumped substantially to the west correlating with a global sea level drop during Gordon Stray deposition. The influence of structural features may have not been as prominent to the south.