Master of Science (MS)
Geology and Geophysics
The Carboniferous Lower Atoka outcrops in the Arkoma Basin of Central Arkansas contain turbidite deposits in a channelized and unchannelized submarine fan setting. The objectives of the study were to determine depositional characteristics and reservoir performance of these fine-grained submarine fan deposits. Four outcrops (Highway 5, Perryville, Chula, and Danville) were studied and described in detail emphasizing sedimentary facies, vertical succession of beds, sedimentary structures, and other small-scaled features that cannot be resolved in subsurface deposits. Five distinct sedimentary facies were recognized: Facies A - massive sandstones, Facies B - thin-bedded sandstones with a mudstone drape, Facies C - interbedded thin sandstones and mudstones, Facies D - chaotic deposits, and Facies E - mudstone. Facies and sedimentary characteristics of the outcrops provide clues as to which deepwater sub-environment the facies were deposited. On the basis of field criteria, the outcrops were characterized as channelized, channel or channel margin deposits, or unchannelized, sheet sand deposits. Channel deposits are massive fine-grained sandstones (facies A), with occasional scouring at the base and rip-up clasts throughout. Channel margin deposits consist predominately of interbedded thin sandstones and mudstones (facies C) with many of the sandstone beds containing small-scaled ripples and laminations. Sheet sand deposits are from lower-energy flows with the presence of more sedimentary structures, less scouring and a higher net-to-gross than the channelized deposits. Highway 5 and Perryville outcrops were deposited in a middle fan environment as channel and channel margin deposits. Danville and Chula outcrops were deposited in a lower fan setting as sheet sands. There are several potential source terranes for these deposits determined from point counting and detailed analysis of tourmaline crystals, which suggest that the main source consisted of sedimentary and metasedimetary rocks from the Appalachians with possible sediment transport from the craton interior: the Illinois Basin.
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LaGrange, Kelly R., "Characterization of the Lower Atoka formation, Arkoma Basin, Central Arkansas" (2002). LSU Master's Theses. 747.
Arnold H. Bouma