Publication Date


Document Type


First Advisor

Webb, Peter-Noel

Degree Name

M.S. (Master of Science)


Department of Geology


Geology--Arkansas||Petrology--Arkansas||Geology, Stratigraphic--Pennsylvanian


The Atoka Formation, an early Pennsylvania clastic succession up to 28,000 feet thick, occurs within the Ouachita Mountains and Arkoma basin of Arkansas. Deltaic, continental shelf, and deep-sea fan systems deposited clastic sediment into a westerly trending geosynclinal trough. A depositional model has been constructed illustrating relationships of depositional systems and their associated facies. The basin filled quickly with clastic material derived from cratonic and extracontinental sources. The cratonic sediments were dispersed chiefly by shallow water dispersal systems that inter- fingered with a deep-water fan system supplied by extracontinental elastics. A paleocurrent study using sole markings and ripple marks indicates bi-directional material discharge. Ripple marks in shallow-water deltaic and continental shelf sandstones generally indicate southerly flow directions whereas deep-water turbidites repeatedly show west to southwest flow directions. Active deposition with synchronous subsidence gave rise to down-to-the-basin growth faults, resulting in collapse of the northern shelf and migration of the trough axis northward. A period of major mountain building during late Atoka deposition created numerous east-west trending thrust faults, anticlines, and synclines in the Ouachita province, but there appears not to have had any effect on sediment composition.


Includes bibliographical references.


123 pages




Northern Illinois University

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