Abstract: Integration of Photomosaics and Stratigraphy in the Western Appalachian Basin as an Aid to Identify Potential Hydrocarbon Reservoirs

Marilyn D. Wegweiser

Paleozoic stratigraphy of the southern Lake Erie region is commonly interpreted as being dominated by flat-lying sedimentary rocks. Recent surface stratigraphic studies in New York, Pennsylvania, and Ohio have revealed the widespread presence of NW- and NE-trending folds and faults exposed along stream beds, and in bluffs along the southern Lake Erie shoreline. A black shale unit, previously unknown in northwestern Pennsylvania, was also discovered and its lateral continuity mapped. The shale forms a disconformable contact with the overlying Northeast Shale.

Ship-based photomosaics were made of bluffs along Lake Erie, and integrated with land-based stratigraphic sections to map the continuity of units, identify displacement zones, and identify low amplitude folds. The black shale unit aided identification of offset and folding. Faults observed at the surface offset Devonian and Mississippian rocks, and unconsolidated Quaternary sediments. Subsurface wrench faults, apparently extending into Precambrian rocks, have been identified by others. These wrench faults are generally perpendicular to the strike of the Appalachian Mountains, and are known as cross-strike discontinuities (CSDs). Principle zones of displacement associated with the CSDs can be recognized at the surface by numerous fractures having little offset, aligned drainage systems and zones of increased hydrocarbon productivity and fluid migration. Increased hydrocarbon production occurs where reservoirs are cross-cut by the faults. The faults offset various reservoirs in Pennsylvania and Ohio in the subsurface. Identifying the location of these faults at the surface may provide information that leads to the discovery of new potential reservoirs.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas