Date of Graduation

12-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Geosciences (PhD)

Degree Level

Graduate

Department

Geosciences

Advisor

Walter Manger

Committee Member

Doy Zachry

Second Committee Member

Ralph Davis

Third Committee Member

Mohamed Aly

Fourth Committee Member

John Hehr

Keywords

Sandstones, Sedimentology, Southern Midcontinent, Southern Ozarks, Stratigraphy, Tectonostratigraphy

Abstract

The Paleozoic stratigraphic record of the Ozark Region, southern midcontinent has been divided into at least 33 formations, with the most significant thickness of 9692 feet preserved in northwest Arkansas. The potential thickness would have been much greater, but epeirogenic movements and sea-level rise and fall produced regional surfaces of erosion reducing the record. That interplay between tectonics (epeirogenic movements) and eustatic change (transgressive-regressive cycles) preserved in the Ozark sedimentary history provides the basis for recognition of five distinct, but related, tectonostratigraphic units designated TS 1 through TS 5: Late Precambrian-Middle Cambrian (TS 1), Late Cambrian-Earliest Ordovician (TS 2), Early Ordovician-Early Devonian (TS 3), Middle Devonian-Late Mississippian (TS 4), and Early-Middle Pennsylvanian (TS 5), and a better understanding of the effects of two independent, but potentially simultaneous, processes: eustasy – variation of ocean water volume, which causes sea-level rise and fall and controls sediment supply; and tectonism – changes in elevation of earth’s crust, either by uplift or subsidence, providing or reducing accommodation space and ultimately recorded sedimentary succession.

The studies of the stratigraphic succession preserved in the southern midcontinent illustrate the interaction of tectonics, eustasy, as well as the effects of weathering, erosion, transport, and depositional processes through the Paleozoic Era. This succession of events is recorded in the stratal configurations, stratigraphic style, and lithologic changes in the geologic record of the southern Midcontinent. The three studies examine the evidence and interpret the record of compositional evolution with the tectono-stratigraphic sequences, the source and delivery conundrum for the terrigenous clastic sediments, and finally, the regional tectonic history of the southern Ozark Dome and its effect on the stratigraphic succession. While perhaps leaving some questions still unresolved, this is the first study that has recognized and “read” the record of these tectono-stratigraphic sequences in the southern Midcontinent.

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