Semester

Summer

Date of Graduation

2005

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Thomas Kammer.

Abstract

The Upper Pennsylvanian Glenshaw Formation contains a series of marine zones that were deposited on the detrital slope of the Appalachian highlands during the last major transgressions from the Midcontinent Sea in the Paleozoic of eastern North America. These marine zones contain distinctive fossil assemblages characterized as biofacies that inhabited a variety of shallow marine environments.;The first chapter of this paper focuses on the Ames marine zone sampled along a northwest-southeast transect across the Appalachian Basin. The Ames marine zone was deposited during the most extensive marine transgression of the Pennsylvanian in this region. Gradient analysis of the proportional abundance of taxa reveals an environmental continuum along which four biofacies were distributed. Biofacies distribution is interpreted to be controlled by salinity, turbidity, and oxygen gradients related to the proximity to eastern terrigenous source areas and relative sea-level change.;The stratigraphic range of this study is expanded in the second chapter and third chapters was expanded to include the Lower Brush Creek Upper Brush Creek and Cambridge marine zones. The geographic range is also expanded to include exposures in four separate geographic regions in the Appalachian Basin. Gradient analysis of the proportional abundance of taxa reveals an environmental continuum along which five biofacies were distributed. The distribution of the five biofacies along the gradient is interpreted to be controlled by the degree of environmental stability. The degree of environmental stability fluctuated during the establishment of marine faunas in the Glenshaw Formation due to the rate of relative sea level change, geographic position relative to the source of marine influence, geographic position relative to eastern terrigenous source areas, and the relative extent of the four marine incursions.;Biofacies within the Glenshaw Formation re-appear with a distinctive composition-abundance structure tracking a preferred set of environmental conditions. The eight most abundant genera were non-randomly distributed, indicating a consistent environmental preference. Only four of the remaining 15 less abundant genera were non-randomly distributed. The abundant taxa maintain a more consistent membership within biofacies by tracking their preferred environment. This pattern is consistent with an independent response of taxa to changing environmental conditions.

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