Semester

Summer

Date of Graduation

2007

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Thomas Kammer.

Abstract

The Fivemile and Eads Mill members of the upper part of the Hinton Formation are two significant marine zones that occur within the Mauch Chunk Group in southwestern Virginia and southern West Virginia.;Multivariate analyses of binary fossil data for the Fivemile Member were performed in order to determine any underlying paleoecologic signals. Analyses of the data sets indicate that this member is dominated by a euryhaline fauna in four of the five locations studied. Euryhaline fauna characteristic of the Fivemile Member include the brachiopod Lingula, the bivalves Modiolus and Septimyalina, and ostracods. The geographic distribution and richness of these dominant fauna decreases to the southwest and the northeast, whereas the overall thickness of the Fivemile Member decreases to the northeast. This pattern indicates that more open-marine conditions existed in the south-central field area during deposition of the Fivemile Member. The one locality containing an open-marine fauna is thought to represent a deeper portion of the Appalachian Basin in a possible marine embayment where more open-marine conditions were established.;A comparative analysis of the paleoecology between the stratigraphically older Fivemile Member and the overlying Eads Mill Member reveals a distinct difference in their respective fossil assemblages. Whereas the Fivemile Member represents a marine transgression of limited extent in the study area, the Eads Mill Member fauna suggests a subsequent, larger magnitude relative sea level rise. The Eads Mill Member fauna includes diverse assemblages of various brachiopods, rugose corals, and bivalves. The Fivemile Member faunal assemblage appears to be a subset of the taxa present within the Eads Mill Member. The primary control on the stratigraphic distribution of various taxa present within and between the Fivemile and Eads Mill members appears to have been salinity. This salinity contrast is remarkably clear when selected stratigraphic sections of the Fivemile and Eads Mill members are stacked on top of one another, and their Detrended Correspondence Analysis axis 1 (DCA 1) scores are plotted stratigraphically. The Fivemile Member, with its dominantly euryhaline fauna, has strong positive DCA 1 scores, whereas the Eads Mill Member, with its more stenohaline fauna, has low positive to negative DCA 1 scores. These results suggest that the use of DCA 1 scores can serve as a useful proxy for studying the relative salinity gradients that may be present in many other paleoecologic data sets of Late Paleozoic age.

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