Date of Graduation

12-2019

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor

T.A. (Mac) McGilvery

Committee Member

Celina Suarez

Second Committee Member

Robert Liner

Keywords

Arkoma Basin, Atoka, Complex Faulting, Cross section, Deep Basin, Deep Marine Deposits, Eustacy, Sandstone complexes, Tectonostratigraphy, Transect

Abstract

The east-to-west oriented Arkoma Basin is a peripheral foreland basin or depositional trough that developed during the Carboniferous Period. This formation covers an aerial extent of approximately 33,800 square miles and spans from west-central Arkansas into southeastern Oklahoma (McGilvery, Manger, and Zachry, 2016; Perry, 1995). The Atoka Formation, deposited during the early Pennsylvanian, is the largest Paleozoic formation by aerial extent in the state of Arkansas and is located within and comprises the bulk of Arkoma Basin sediments (McFarland, 2004; Nance, 2018). This formation has been informally divided into three divisions, the lower, middle, and upper, based on their stratigraphic response to differing tectonic processes.

A tectonostratigraphic interpretation was made for each division of the Atoka Formation using high resolution cross sections; correlated using well log, seismic, and surface data. Five condensed regional transects were constructed that aided in the development of a cross section “grid” meant to represent the deep marine to shallow marine depositional hinge lines.

Each of the three Atoka divisions have a different dominant depositional force. The Lower Atoka deposition was dominated by eustasy, and with sediment supply from the start of Arkoma Basin tectonics, the middle division was dominated by tectonic subsidence and the upper was dominated by sediment supply. The transition between the Atoka divisions and the magnitude of migration between each deep marine hinge line indicates the progradation of the Upper Atoka depositional cycles occurred more rapidly than the retrogradation of the Middle Atoka. The maximum flooding of the formation occurred within the Middle Atoka’s uppermost informal member, the Morris Member. The Lower Atoka was deposited on an extensive tectonically stable structural platform, which is supported by no lithostratigraphic transition to deep marine deposits within this project’s study area. The deep marine deposition is characterized by shales encapsulating tumultuously distributed and isolated sandstone complexes. These sandstone complexes are not correlated to the shallow marine sandstones by anything but a condensed geologic timeline.

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