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The AAPG/Datapages Combined Publications Database
Detailed surface mapping, combined with investigations of two deep wells, nearby seismic profiles, and other studies enabled construction of detailed cross sections to basement across the Nittany anticlinorium of West Virginia.
Mapping shows the local large anticlines to be thrust faulted, to plunge into synclines, and to divide near terminations into several smaller plunging anticlines. Bed-extension structures occur in ductile rocks between noses of anticlines that plunge past each other in opposite directions, and there appears to be an increase in the density of longitudinal jointing in plunging anticlinal noses. Field sections show that much pre-folding shortening occurred by intraformational wedging and solution cleavage.
The northeast-trending Wills Mountain anticline, adjacent to the Appalachian structural front, is a northwestward thrust along the ramping Sponaugle thrust with decreased stratigraphic displacement and throw northeastward. However, northeastward along trend, northwestward forward motion is transferred to a higher level by growth of the Kittlelick thrust and consequently the Hopeville anticline, thus maintaining a consistent surface expression of the Willis Mountain anticline northeastward. The deep structures of the anticlinorium in the Petersburg region consist of several imbricated structural blocks involving Cambrian-Ordovician carbonate rocks, with small net slips on southeast-dipping reverse faults located east of the larger Wills Mountain structural block.
Shortening estimated from the cross sections reveals relative age relations of major structures, ramping thrusts, and decollements within the Nittany anticlinorium and also allows predictions of amounts of shortening and deformation outside the anticlinorium. Most structures in the Petersburg region developed by a west-northwest-directed gravity-spreading mechanism in which decollements allowed the ductile units to shorten nearly twice as much as the more rigid units.
The study provides insight for exploration for potential hydrocarbon resources within numerous subsurface, perhaps complex, structural traps and areas of increased fracturing in which effective permeability has probably been increased, particularly in the Devonian shale.
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