Chaoqing Yang

Date of Graduation

1998

Document Type

Thesis

Abstract

This study was designed to analyze the perplexing Carboniferous stratigraphy in the study area using a sequence-stratigraphic approach in conjunction with lithostratigraphic and subsurface mapping methods. A regional stratigraphic framework is established for the uppermost Devonian to Middle Pennsylvanian interval in the study area using a network of well-log cross sections. Lithostratigraphic units are correlated throughout the study area mostly at formation level; most of the units are correlated from the subsurface to their outcropping equivalents. Four sequences are identified within the study interval, based on the recognition of sequence-bounding unconformities, condensed sections and stacking patterns. The sub-Ravencliff unconformity is recognized by this subsurface study as a regional angular unconformity within the Mauch Chunk Group. Of the five sequence-bounding unconformities, the sub-Ravencliff and sub-New River unconformities were probably related to loading relaxation, whereas the sub-Berea, sub-Greenbrier, and sub-"Mahoning" unconformities likely resulted from post-orogenic rebound in terms of flexural foreland-basin models. From the latest Mississippian to Early Pennsylvanian, the study area experienced significant change in drainage pattern. The drainage systems of stage 1 (at Mississippian-Pennsylvanian transition) in the study area flowed mostly northwestward, whereas those of stage 2 (Early Pennsylvanian) flowed southward and southwestward. The incised-valley systems along the sub-Ravencliff and sub-New River unconformities are analyzed with detailed cross sections and isopach maps. Generally, the paleovalleys were filled first with quartz-rich fluvial sands during stillstand and the following transgression, and then mostly with clays as marine influence increased. Basement reactivation profoundly influenced the depositional thickness, lithofacies, subaerial erosion, drainage system, and structural development during the Carboniferous. The occurrences of the Burning-Mann, Summersville and Beckley faults are suggested by stratigraphic evidence from this study. A buried anticline, the Gauley Mountain, is delineated within the Upper Mississippian interval with evidence from cross sections and isopach maps. Finally, Carboniferous basin history of the central Appalachian foreland basin is summarized in terms of intra-basinal basement reactivation, change in regional tectonic regime, migration of basin center and depocenter, and shift of source area and paleocurrent direction.

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