The University of Tennessee at Chattanooga
Geology Program
Department of Physics, Geology and Astronomy
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dew@mail.cdc.net
Chattanooga Outcrops
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Dewayne A. Ponds and Greg Slater
April 6, 1999
Location
The plunging surface of the Fort Payne Formation (Lookout Valley Anticline) is located in southeast Tennessee just south of Soddy Daisy and approximately 12 miles north of the Olgiati Bridge (US 27) in Hamilton County, Tennessee. This anticline is located within the USGS 7.5-minute Daisy Quadrangle in UTM Zone 16, at coordinates 3,897,700 N and 660,860 E (see Figure 1). From Chattanooga, take US Route 27 (Corridor J) north to the Chickamauga Dam Exit. Exit here and turn left (North) onto Old Dayton Pike. Travel approximately three miles north and turn left on Johnson Road across from Johnson Cemetery. The eastern limb of the anticline begins just across the creek-bridge and is visible on both sides of the road. The western limb is exposed approximately 100 yards further on Johnson Road.
The parking space is extremely limited, and the road features
blind curves and narrow shoulders. It is recommended that visitors
park in the parking lot near Old Dayton Pike and walk the short
distance to the outcrop. The north side of the road is private
property, and the owners rights should be respected.
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Figure 1. Map showing the location of the exposures on Johnson Road (black arrow). (Modified from USGS 1:100,000-scale Chattanooga Tennessee Quadrangle.) |
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Introduction
This site lies within the East-Central, Valley and Ridge Province of the Tennessee Geologic Map, and it marks the northern-most extent of the Lookout Valley Anticline. This province consists of Alleghenian-deformed sedimentary rocks from the Paleozoic. Locally, this deformation resulted in folds and thrusts. In Hamilton County, the anticlinal-folds still exposed are capped and supported by a weather-resistant chert formation. This particular outcrop provides views of the Mississippian Ft. Payne Formation and the Mississippian/Devonian Chattanooga Shale.
The Lookout Valley Anticline is an upright plunging fold, which begins in the south near Dade County, Georgia. The fold trends northeast across the state line between Lookout Mountain and Tiftonia. It continues northeast into Tennessee west of Red Bank and east of Walden Ridge.
Structural measurements were taken here to more accurately delineate this fold's characteristics.
Site description
This site is a roadcut that is near perpendicular to the axial surface of the anticline. This roadcut is actually the result of a joint surface that has been breached by a small creek. Thus, little excavation was necessary to construct the road.
The south side of the road provides views of the Ft. Payne chert. This side is undeveloped (see Figure 2), and the contact between the Ft. Payne chert and Chattanooga Shale is soil covered. However, the north side has recently been excavated for private residential development, and the contact is visible on both limbs. This contact is shown on the map in Figure 3 along with structural data and a structure section. Although the contact between the Newman Limestone and the Ft. Payne Formation is not visible at this outcrop, the contact has been interpreted from the Geologic Map of Hamilton County (Milici and others, 1978).
The importance of this stop is two-fold. (1) This outcrop provides excellent vantage points near the axial surface in which both limbs of the anticline are visible. (2) One can actually see the plunging surface of an anticline just before it disappears. The anticline is asymmetric, and poles to strike planes are plotted in figure 4B. From this plot, a cylindrical best-fit fold axis reveals the trend and plunge (038, 02 degrees) of the axial surface.
Recorded joint measurements reveal two sets. These sets are roughly perpendicular to each other (see Figure 4A), and they are similarly oriented to those found on Walden Ridge. The primary set has been interpreted to be responsible for the truncation of this anticline through which roads have been constructed (see Figure1). While this outcrop is the northern-most expression of this anticline, other exposures are visible via the two roads south of Johnson Road (Jackson Road and Falling Water Road, see Figure 1).
Milici, Robert C., Wilson, Robert L., Maher, Stuart W., Leamon, Alvin R., Knox, Larry M., and Johnson, Robert W., Jr., 1978, Geologic Map of Hamilton County, Tennessee: State of Tennessee, Department of Conservation, Division of Geology, Bulletin 79, Plate 1.