Abstract

The Tyrone-Mt. Union Lineament has been projected into the Appalachian Plateau where it defines a cross-strike structural discontinuity. Geomorphic evidence of the lineament is recorded in Mississippian and older rocks. Near surface hydrocarbon measurements, reservoir gas analysis, fracture measurements, borehole surveys, and very low-frequency electromagnetic data indicate that these lineaments are zones of increased fracture permeability with enhanced hydrocarbon and fluid migration. In one gas field, wells drilled along the lineament had significant gas shows in organic-rich Devonian shales. Several Devonian through Early Pennsylvanian formations have facies and thickness variations across this lineament. These data suggest that the lineament marks the southern boundary of an uplift in north-central Pennsylvania. This uplift boundary is recognized in northwestern Pennsylvania in surface and subsurface data. Farther southeast, where Allegheny deformation was stronger, this subtle boundary is obscured. Subsurface data suggests that this uplift has affected fold terminations and structural elevations. The structural and stratigraphic anomalies overlie a crustal-block boundary. These trends may be explained by differential subsidence of these crustal blocks.--Modified journal abstract.

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