Date of Graduation

12-2020

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor

T. A. "Mac" McGilvery

Committee Member

Walter L. Manger

Second Committee Member

Glenn R. Sharman

Third Committee Member

Jacob F. Grosskopf

Keywords

Chesterian, Fayetteville Shale, Mississippian, Petrography, Provenance, Wedington Sandstone

Abstract

The Wedington Sandstone Member of the Fayetteville Shale is a constructive delta complex in the Chesterian section of the Late Mississippian record in Northwest Arkansas. A comparative analysis of framework grain composition between the Wedington and two other stratigraphically proximal Carboniferous sandstones: the Batesville Sandstone (older) and the Basal Atoka-Spiro Sandstone (younger) has addressed three questions: 1) Is there similarity in sediment provenance for the three sandstones? 2) Do these three sandstone units have a similar sediment dispersal vector? 3) What are likely sediment source terrains for the Wedington Sandstone? Wedington samples overwhelmingly plot as quartzarenites with fewer samples plotting as sublitharenites. Samples from the Spiro also plot as quartzarenites, while Batesville samples contain more lithic and feldspar grains, and plot in the subarkose and sublitharenite fields in Folk’s sandstone classification scheme. This suggests that the Wedington and Spiro sands likely share a common sediment source terrain that differs from that of the Batesville Sandstone. Quartz percentages for the Wedington range from 90.5% to 99.2%. Lithic fragments account for 0.0% to 9.5% of grains and were mostly sedimentary rock fragments. Feldspar grains were exclusively alkali feldspars and account for 0% to 1.4% of framework grains. The Wedington delta complex had a northwest to southeast sediment dispersal vector which is similar to the one proposed for the Basal Atoka-Spiro. The Batesville Sandstone, with its different framework grain composition, was dispersed from north-northeast to south-southwest focused through the Illinois Basin. This vector which predates the Spiro and Wedington systems becomes one of the dominant supply systems for the remainder of the Pennsylvanian fill across central Arkansas. Sediment for the Wedington was likely derived from a mix of source terrains including: the Nemaha Ridge, an older recycled sandstone unit, the Appalachian Mountains, and the Canadian Shield.

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