Date of Graduation

5-2024

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor/Mentor

McGilvery, Thomas

Committee Member

Sharman, Glenn

Second Committee Member

Shaw, John

Keywords

Arkansas; Arkansas River; Geomorphology

Abstract

The Arkansas River is one of several large and important river systems stretching from the Rocky Mountains to the Mississippi River. It meanders across the Great Plains for ~1000 km before plunging into a mountain-bound valley, confined by the Ozarks to the north and Ouachitas to the south. The geologic history of the Arkansas River is poorly understood and crudely constrained to sometime between ~60 Ma and 100 Ka. Questions remain concerning its path(s), potential integration of the upper and lower sections, and overall history. The combination of knickpoint and chi (χ) mapping, tributary grain size analysis, tensile strength testing, and tributary-mainstem angle analysis demonstrates that the lower portion of the Arkansas River was likely once two discrete rivers flowing in divergent directions from a divide near Ozark, AR, suggesting that a portion of the lower Arkansas was not integrated with rivers draining the Rocky Mountains or flowing across the high plains, but rather was a much smaller river, flowing east to west. Upwards of 80% of all knickpoints in the region are concentrated in Ozark tributaries with anonymously large tributary junction angles and with a median grain size eight times larger below knickpoints compared to those above. This pattern suggests adjustment to a base-level change in a region lacking structural or lithologic variation. This analysis suggests that divide migration and stream capture caused a partial flow reversal, dictating the modern route and flow direction of the Arkansas River

Included in

Geomorphology Commons

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