Semester

Summer

Date of Graduation

2006

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Richard Smosna.

Abstract

Subsurface correlation of well-logs and isopach mapping of Upper Devonian-Lower Mississippian units have been coupled with outcrop measured sections to determine the nature and distribution of Upper Devonian-Lower Mississippian sandstones in southwestern Pennsylvania. The stratigraphic section studied ranges from the Upper Venango Formation to the Price Formation and includes the Hundred Foot, Murrysville (Cussewago/Berea) and Weir sandstones of southwestern Pennsylvania. Isopach maps were generated for the Hundred Foot sandstone, Oswayo Shale, Murrysville sandstone, Riddlesburg Shale, and Weir sandstones as well as eight cross-sections across the study area. The resulting sediment distribution patterns along the developing edge of the Late Famennian-Early Tournaisian foreland basin were dominantly barrier bar, fluvial, braid-delta and shoreface in nature. Evaluation of the isopach geometries suggests that these depositional systems were influenced both by pre-existing structural features and eustatic fluctuations. The author suggests that a strike-parallel structural feature, namely a Rome Trough graben fault, and cross-structural discontinuities (CSDs or lineaments) may have acted as barriers and pathways during sediment deposition in the developing Acadian basin. All three majors sandstones in this study show dramatic facies changes on opposing sides of a southwest-northeast trending Rome Trough basement fault suggesting that this fault may have been active, both in normal and reverse directions, during collisional pulses of the Acadian orogeny. The Devonian Hundred Foot sandstone displays a noticeable thickened section on the west side of the Rome Trough fault, while the Devonian Murrysville sandstone displays a distinct facies change from fluvial to deltaic across the fault. The Mississippian Weir sandstone, in contrast to the Hundred Foot, displays a thickened section on the east side of the basement fault. In addition, northwest-southeast trending CSDs, namely the Blairsville-Broadtop Lineament (B-BL) and the Pittsburgh-Washington Lineament (P-WL), may have influenced fluvial channel positions and acted as sediment traps. Both the Murrysville and Weir sandstones show fluvial channel incision as well as facies changes near these proposed lineaments.

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