Masters Theses

Date of Award

12-1982

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Thomas W. Broadhead

Committee Members

Robert E. McLaughlin, Kenneth R. Walker

Abstract

The strati graphic sequence of east Tennessee Middle Ordovician late LIanvirn-Llandeilo carbonate facies at Cedar Springs (Copper Creek Allochthon), Silver City and Douglas Lake (Bays Mountain Synclinorium) provides a unique lithologic framework for the study of conodont faunas, their biostratigraphy and paleoecology. These three sections correlate with previously published sections primarily on the first appearance of Phragmodus sp. A and Polypiacognathus friendsvillensis.

During pre-Phragmodus sp. A time, portions of the Knox Group were subareally exposed with considerable topographic relief. "Mosheim" and "Blackford" lithologies represent thin patches of carbonate mud which washed into topographic depressions. During Phragmodus sp. A time the northwestern extension of a Knox topographic low (Cedar Springs) was open to the transgressing sea establishing intertidal conditions which opened onto a shallow shelf (Douglas Lake and Silver City) on which argillaceous limestones of the lower main body of the Lenoir Formation were deposited.Polypiacognathus friendsvillensis time marked the shelfward migration of the shelf edge, establishing deeper water conditions in the eastern most part of the study area evidenced by deposition of the Fetzer Facies of the Whitesburg Formation.

The distribution of conodont species in shallow water, carbonate restricted and normal marine facies, inferred from petrologic analysis, suggests that environmental controls were species specific. Salinity and temperature appear to have been the major controlling factors affecting conodont distribution (i.e. PIectodina? Sp. And P. n. sp. Of Carnes (1975), Leptochiroqnathus semiflorealis and L. quadratus) Species of Phraqmodus display differing environmental distributions. £. sp. A is associated with restricted intertidal channels. Flexuosus specimens are also present in intertidal channels, but peak abundance occurs in subtidal channel facies containing stenotopic shelly fauna. Substrate type appears to control distribution of species such as PIectodina joachimensis in al gaily laminated tidal channel levee deposits. Finally, the distribution of biostratigraphically important species such as Polypiacognathus friendsvillensis is appears to be environmentally controlled, but only excluded from facies deposited in shallow restricted environments. Consequently, conodont biostratigraphy should include consideration of possible ecologic controls affecting species distribution.

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