Morris, Robert C. (Robert Clarence), 1928-||Odom, J. Edgar||McGinnis, Lyle D. (Lyle David), 1931-2017
M.S. (Master of Science)
Department of Earth Science
Carbonate rocks||Geology, Structural
A geologic map has been constructed of upper Mississippian and lower Pennsylvanian sedimentary rocks for a portion of the Frontal Quachitas of Arkansas between Arkansas Highway 7 and Highway 9. These rocks consist of 17,000 feet of flysch-type unmetamorphosed sandstones and shales which have been folded and thrust-faulted into an east-west trending belt. Two major stratigraphic units were recognized; the Stanley and Jackfork Groups of Carboniferous age. The Tenmile Creek, Moyers, and Chickasaw Creek Formations of the Stanley Group were mappable, although only the Chickasaw Creek is completely exposed. The exposures of the Chickasaw Creek represent the easternmost reported occurrence of this formation. The Jackfork Group in the map area lacks the stratigraphic markers necessary to divide it according to Oklahoma terminology, but the two-fold subdivisional scheme practiced by other workers at Northern Illinois University has proven to be workable. Petrographically, Stanley sandstones are poorly sorted, fine grained and contain an average of 6.4% feldspar and 10% rock fragments. The average matrix content in Stanley sandstones is 23%. Jackfork sandstones are moderately sorted, fine grained and contain only traces of feldspar and rock fragments. Quartz constitutes more than 97% and matrix generally less than 5% of the Jackfork sandstones. Irons Fork Mountain shales contain illite, mixed-layer material (illite-montmorillonite) and minor amounts of chlorite. The only definite provenance is interpreted to have lain to the east during Stanley-Jackfork time. Lateral sources may have been contributors but are not clearly evident. Slump deposits (chaotic shales and sandstone blocks) are interpreted to have been derived from unstable northern flanks. Sub-deltaic features suggest the rocks were deposited near the eastern point source. Westward flowing turbidity currents and some normal bottom currents dispersed the sediment. Thrust faults and folds dominate the deformational effects. Two faults are named and defined; the Walnut Bottom thrust fault and the Lake Sylvia fault. The White Oak Mountain syncline and Little Cedar Creek anticline are also defined. One large folded thrust is interpreted to underlie the entire area. Only one imbricate to this fault was found, the Walnut Bottom fault. Gravity glide, generated by a southern uplift is postulated to explain the bedding plane thrusts. Further application of the same stress patterns was subsequently released through folding.
Burkart, M. R., "Stratigraphy, structure, and petrography of carboniferous rocks from Crystal Mountain region, Arkansas" (1969). Graduate Research Theses & Dissertations. 5069.
vi, 75 pages
Northern Illinois University
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