Masters Theses

Date of Award

12-1986

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Thomas W. Broadhead

Committee Members

Kenneth R. Walker, Robert McLaughlin

Abstract

The Fetzer Formation is a thin (averaging approximately 1,5 meters at the study sections) echinoderm-rich/ dark, skeletal limestone unit of Middle Ordovician age that crops out in the eastern Valley and Ridge province of Tennessee and southwestern Virginia. It overlies the Lenoir Formation and is overlain by the Whitesburg (where present) and Blockhouse formations. The Fetzer is interpreted as being deposited in a shelf edge to upper slope and deep ramp transitional environment. The environment of the Fetzer became progressively deeper as a result of the downwarping of the Blountian Phase of the Taconic Orogeny; this subsidence appears to have been more rapid toward the northern sections.

The Fetzer was deposited as both autochthonous grains (chiefly echinoderm debris) and allochthonous sediment that was swept into the area from shallower water by storms and currents. The Fetzer was largely below the effective photic zone in 50-150 meters of water, with exposures at Douglas Lake and Rich Mountain probably representing shallower depths than those at the other three sites studied. The probable depth, lack of algae, and perhaps unusual water and/or sediment chemistry may account for the low diversity of fossilized organisms. The conodont faunas are highly variable in abundance (0-55 specimens/kilogram), with conodont color alteration indices (CAI) of 3-4.

Most sections contain conodonts typical of the North Atlantic conodont biogeographic province, supposedly representing a predominantly deep, cool water association. Some localities (Rich Mountain and Douglas Lake), however, have conodonts from the deeper biofacies of the North American Midcontinent province, which probably preferred slightly warmer, shallower water environments than most North Atlantic species. Where these provincial water masses apparently came into contact in the area of Fetzer deposition, there is evidence of competitive exclusion between the North Atlantic Periodon aculeatus and the superficially morphologically similar North American Midcontinent species Phraqmodus flexuosus.

Biostratigraphically, all five localities studied are in the Pygodus serra Zone, and where further definition is possible, they lie in the Eoplacognathus foliaceus subzone. Transitional and late forms of Cahabagnathus friendsvillensis indicate that the base of the Fetzer at Silver City, Tennessee, is slightly younger than the other localities studied.

At Mosheim, several specimens of Protoprioniodus simplicissimus were recovered. The presence of numerous specimens of Pygodus serra both above and below the sample that yielded the Protoprioniodus simplicissimus specimens indicates that this is, apparently, the latest occurrence of this species thus far recorded.

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