Masters Theses
Date of Award
6-1985
Degree Type
Thesis
Degree Name
Master of Science
Major
Geology
Major Professor
Steven G. Driese
Committee Members
Richard Arnseth, Kenneth Walker
Abstract
The Clinch Sandstone is exposed along a 2 kilometer transect through Beans Gap on Clinch Mountain in northeastern Tennessee. The two members of the Clinch Sandstone, the lower Hagan Shale Member (14.9 m) and the upper Poor Valley Ridge Member (55.7 m), are both present and can be divided into distinct facies. The three facies of the Hagan Shale Member compose a coarsening-upward sequence that includes shelf-mud deposition at the base and transition-zone deposition at the contact with the Poor Valley Ridge Member. These deposits are characterized by a rather diverse assemblage of trace fossils including Arthrophycus, Skolithos, Rusophycus, Monocraterion, Planolites, and possible Chondrites. The Hagan Shale Member is composed of subarkosic clayshale, siltstone, interbedded clayshale and siltstone and thin- to medium-bedded quartzitic sandstone. Paleocurrent indicators are rare in the Hagan Shale Member.
The Poor Valley Ridge Member can be subdivided into four facies at Beans Gap. Each represents different environments of deposition. Facies 1, characterized by medium- to large-scale trough cross-stratification, represents depositional conditions with flow velocities of 70 to 90 cm per second but interrupted by sus pension deposition of clays and bioturbation. Facies 2 exhibits medium- to very large-scale planar-tabular cross-stratification and represents flow velocities of 60 to 80 cm per second during episodes of deposition more continuous than those of facies 1 . Facies 3 is characterized by very densely bioturbated sandstone, which represents periods of low-energy and reduced sediment influx. Fades 4 represents deposition characterized by alternating high-energy events (which deposited horizontally laminated and rippled sandstone) and low-energy events (suspension deposition of clays followed by bioturbation).The Poor Valley Ridge Member contains Arthrophycus, Skolithos, Rusophycus, Cruziana, Monocraterion, Diplocraterion, Planolites, and possible Thalassinoides. Each of the fades and trace fossils present represent deposition in a subtidal, marine environment with probable water depths between approximately 3 and 20 m. Vertical sequences within the Poor Valley Ridge Member were analyzed with a statistical comparison to random occurrence. The analysis yielded two preferred paths which can be described as "lowenergy" and "high-energy." Paleocurrent directions for the Member, when examined in conjunction with facies and facies sequences suggest deposition in three laterally shifting shallow-marine environments; the shoreface, rip channel/tidal inlets, and a back-bay or lagoon. A prograding sequence from the top of the Hagan Shale Member to a thinly laminated siltstone in the middle of the Poor Valley Ridge Member reverses to a brief transgressive sequence consisting of rip current/tidal inlet and shoreface deposits. These are in turn over lain near the top of the Formation by more rip current/tidal inlet and uppermost shoreface deposits. An unconformity occurs at the top of the Clinch Sandstone at Beans Gap.
Detailed sampling and point-counting yielded extensive mineralogic data which was compiled and statistically treated with correlation coefficients to determine occurrence relationships between the minerals. Few noticeable trends and relationships were found in the Formation, but the compilation allowed comparisons to be drawn between the Clinch Sandstone in northeastern Tennessee and the Tuscarora Formation in Virginia and Pennsylvania. The Clinch Sand stone in Tennessee is apparently derived from a more mature source (throughout almost its entire deposition, unlike the Tuscarora Formation in Virginia), perhaps the Cambrian Chilhowee Group, and represents deposition in a shallow-marine setting; it does not show any fluvial facies, such as are found in the Tuscarora Formation to the north.
Post-burial features have been noted and porosity has been measured from the thin sections. These suggest several stages of authigenic mineral precipitation and dissolution which occluded much of the original porosity but also formed secondary and hybrid pores that are present today in amounts averaging 3% and ranging up to 11%.
Recommended Citation
Schoner, Amy Elizabeth, "The sedimentology and sedimentary petrology of the Lower Silurian Clinch Sandstone at Beans Gap, Grainger County, Tennessee. " Master's Thesis, University of Tennessee, 1985.
https://trace.tennessee.edu/utk_gradthes/14437