EAST TENNESSEE GEOLOGICAL SOCIETY
2007 Spring Field Trip

Structural Geology of the Chattanooga Area

Hamilton County, Tennessee
Saturday, April 14, 2007

 

Trip Leaders

Dr. Jonathan W. Mies
Robert Lake Wilson Associate Professor of Geology
University of Tennessee at Chattanooga

Mark Gardiner
Shaw Environmental & Infrastructure


Attendees

 

View of downtown Chattanooga and Moccasin Bend
from Point Park, a prominent Civil War battlefield on Lookout Mountain.

Digital terrain rendered from USGS 10-m digital elevation data for various quadrangles in the Chattanooga area. Observer is 500 meters above Lookout Mountain at the Georgia/Tennessee state line (35.000 N, 85.347 W) looking north, over the shoulder of Point Park. Geologic cross section is revealed by a 1-kilometer-wide trench. Geology interpreted from Milici and others (1978, Geologic Map of Hamilton County, Tennessee: State of Tennessee, Department of Conservation, Division of Geology, Bulletin 79, Plate 1).

 

Rendered 10-meter digital elevation model (DEM) of part of the Fairmount Quadrangle showing the Lookout Valley anticline. The black layer is Devonian Chattanooga Shale. The Cranmore Cove and Chattanooga thrust faults are shown in red. Pennsylvanian rocks cap the Cumberland Plateau (Walden Ridge/Signal Mountain).


ETGS members traveled to the Chattanooga area on April 14, despite predictions of substantial rainfall. This trip complimented Dr. Mies' presentation at the April 9th ETGS meeting.

The following photographs were made by Brad Stephenson. The apparent autumn colors in some photos resulted from an early-April freeze after an unseasonably hot March.


Following introductions and orientation in a Cleveland parking lot, our first destination was the classic series of road cuts through Whiteoak Mountain (officially designated White Oak Mountain by the U.S. Geological Survey). This site straddles the boundary between Hamilton and Bradley counties along I-75 (between mile markers 14 and 16) and provides exposures of portions of the Whiteoak Mountain synclinorium, including dramatic examples of the faults and folds that characterize the Valley and Ridge province (Wilson, 1986).



A scenic overlook on the western slope of Whiteoak Mountain provided an opportunity to review maps and cross-sectional diagrams of the features observed in the road cuts, as well as a view of the gently dipping beds of the Ordovician Catheys and Sequatchie Formations. In this area, the Silurian Rockwood Formation may be observed as gently dipping beds below remnants of the Devonian Chattanooga Shale, as well as higher-angle beds which have been thrust above that layer (See Figure 4 in
Wilson, 1986). The overlook also provides a view of the western portion of the Valley and Ridge province and Waldens Ridge (Cumberland Plateau).

 



The second component of the trip included visits to a series of geologic features and environmental sites within the former
Volunteer Army Ammunition Plant, which manufactured trinitrotoluene (TNT) for the Army from 1942 until the mid-1970s. Environmental restoration has been underway since the early 1990s, and large portions of facility have been prepared for redevelopment by the City of Chattanooga and Hamilton County as an industrial park.

The geology, stratigraphy, and environmental contamination of the area were examined with emphasis on (1) how the structural geology impacted development of the manufacturing areas, (2) the role of weathering of the parent rocks to residuum soil on the distribution of explosives contamination in soil and groundwater, and (3) the karst geology and its effect on groundwater contaminant distribution in bedrock.



The remainder of the trip included visits to locales north of Chattanooga in the western part of Hamilton County. This segment of the trip focused on the structural geology and fold-related joints in the western portion of the Valley and Ridge province. The photos below show
structures developed in the footwall of the Missionary Ridge fault near Chickamauga Dam, including very small (meter-scale) folds. The green material in the final two photos has been interpreted to be the T3 bentonite, a chronological marker bed which poses significant geotechnical challenges for the planned project to extend the locks at Chickamauga Dam.



A cold deluge descended on us during our visit to the rock outcrops near Chickamauga Dam. The remainder of the trip included exposures of the
Lookout Mountain Anticline, which were viewed from the vehicles, including traverses through the structure at various locations along the axis of the plunging anticline.

Trip leaders, Dr. Jonathan Mies and Mark Gardiner
adjust plans for the final segment of the trip.

 

REFERENCES

Wilson, R.L., 1986, Whiteoak Mountain synclinorium, Bradley County, Tennessee: Geological Society of America Centennial Field Guide--Southeast Section, 1986.


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April 20, 2007