Masters Theses

Date of Award

3-1985

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Robert E. McLaughlin

Committee Members

Thomas W. Broadhead, Kenneth R. Walker

Abstract

Approximately 510 meters of mixed carbonate and terrigenous clastic sedimentary rocks deposited during the Middle Ordovician overly the Athens Formation in the Knoxville-Athens Belt near Calhoun, Tennessee. Nine lithostratigraphic units have been recognized above the Athens Formation from measured sections at Henegar Bluff and along the Louisville and Nashville Railroad cut; these units include from oldest to youngest: the Upper Tongue of the Lenoir Formation; the Holston Formation; the Chapman Ridge Formation which contains a basal "orthocone zone" overlain by the "main body" of the formation; the Lower Unnamed Shale, the Hiwassee, the Middle Unnamed Shale, and the McKnight Members of the Ottosee Formation; and the "Bays" Formation.

Analysis of the conodonts collected during this study suggests that the Upper Tongue of the Lenoir Formation as well as the base of the Holston Formation lie within the Upper Subzone of the Pydogus anserinus Conodont Zone. Based on the evolutionary transition from Cahabagnathus sweeti to Cahabagnathus carnesi found in the Holston Formation at Henegar Bluff, the boundary between the Upper Subzone of the Pygodus anserinus and the Amorphognathus tvaerensls Conodont Zones has been tentatively placed at 9.7 meters above the base of that measured section and approximately 244 meters above the post-Knox unconformity. The remainder of the stratigraphic section exposed within the study area up to and including the lower part of the "Bays" Formation appears to lie within the lower part of the Amorphognathus tvaerensls Zone and possibly lies almost entirely within the Prioniodus gerdae Subzone. Field and petrologic studies have shown that the post-Athens rocks within the Calhoun area represent a complex of carbonate and terrigenous clastic lithofacies deposited in predominately shallow subtidal, shelf to shelf margin environments. The Upper Tongue of the Lenoir Formation contains two lithofacies representative of a back-reef lagoon environment which included a deep subtidal lagoon center subenvironment overlain by a shallow subtidal near-reef subenvironment.

The Holston Formation, which interfingers with the Lenoir Forma tion, contains three lithofacies and represents a shelf margin, skeletal sand bank and reef complex. Algae are common in the Holston Formation in the Calhoun area thus distinguishing the Holston Formation there from most other areas in East Tennessee where this formation outcrops. Inter- and intraformational hardgrounds/corrosion surfaces observed within the Holston may represent the episodic "drowning" of this formation due to a relative rise in sea level coupled with influxes of terrigenous clastic sediment into the Holston environment.

The Chapman Ridge Formation includes two lithostratigraphic units, a basal "orthocone zone" sharply overlain by the "main body" of the formation. The "orthocone zone," which is characterized by abundant cephalopoda and ferromanganese (Fe/Mn) nodules as well as numerous hardgrounds, contains two lithofacies and represents a condensed stratigraphic sequence developed at moderate to shallow water depths along the Middle Ordovician shelf margin. The "main body" of the Chapman Ridge Formation includes three lithofacies which collectively represent a storm? influenced, shallow subtidal, shelf margin, progradational-retrogradational mixed carbonate-terrigenous clastic sand wave environment composed of sand bars and muddy interbar areas.

The Ottosee Formation includes four lithostratigraphic units. The Lower Unnamed Shale Member is very poorly exposed within the study area and may represent muddy shelf and possibly interbar sediments. The Hiwassee Member is composed of two lithofacies which represent deposition in a shelf margin, oolite shoal-organic buildup complex. The Middle Unnamed Shale Member abruptly overlies the Hiwassee Member and is composed of two lithofacies which represent deposition in a storm-dominated carbonate sand/terrigenous sand and mud shelf lagoon. The McKnight Member contains five lithofacies and represents deposition in a shelf margin oolite shoal-organic buildup complex dissected by tidal inlets and channels which typically contain coarse grained mixed terrigenous clastic and carbonate rocks.

The lower "Bays" Formation is composed of one lithofacies and represents sediments deposited along the interface of an oolite shoal complex and a shallow shelf lagoon/sand and mud flat.

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