Date of Award

Spring 8-1-1981

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Geography, Geology, and Anthropology

First Advisor

Donald W. Ash

Second Advisor

Victor C. Miller

Third Advisor

John R. McGregor

Abstract

Karst features in Harrison County, Indiana, and the Mammoth Cave region, Kentucky, are profoundly influenced by lithology and structure. In the Sinkhole Plain two classes of sinkholes, shallow solutional and deeper subsidence, differ in morphology, origin, age, distribution, and density. Distributions of the two kinds of sinkholes reflect the outcrop pattern of specific lithostratigraphic units. Broad shallow dolines (Ste. Genevieve-type sinks) develop on the Horse Cave Member of the St. Louis Limestone and on the Ste. Genevieve, Girkin, and Paoli Limestones. Innumerable steeper-sided subsidence and collapse depressions (St. Louis-type sinkholes) form on the Corydon Chert Member, lower St. Louis Limestone, and perhaps the uppermost Salem Limestone. The geomorphic boundary between sinkhole types coincides with the stratigraphic contact between two subdivisions of the upper St. Louis Limestone, the Corydon Chert Member (proposed her~in), and the overlying Horse Cave Member (Pohl, 1970) . A prominent chert zone in the upper part of the Corydon Chert Member accounts for the position of the geomorphic contact. The Lost River Chert Bed (Elrod, 1899) does not form an areally-extensive structural surface in the Sinkhole Plain. The geomorphic similarity between Harrison County and the Mannnoth Cave region results from two shared aspects: (1) virtually identical structure and stratigraphy and (2) the presence of entrenched streams, within or downdip from the Sinkhole Plain, which have breached the elastic caprock. Parts of the Mitchell Plain and Pennyroyal Plateau lacking such streams (i.e., outside the study area) also lack welldefined bands of sinkholes and of sinking streams which parallel local strike. St. Louis-type sinkholes formed in response to aquifer dewatering effected by Pleistocene entrenchment. Where St. Louis-type depressions are scarce and erratically distributed, topography is essentially relict from the Tertiary. The presence of karst valleys, sinking streams, outliers, and Ste. Genevieve-type sinkholes in these areas indicates that substantial karst development preceded Pleistocene downcutting. The age of the Parker-Blue River strath is pre-Pleistocene and post-Pennsylvanian, probably post-Cretaceous. Karst is pre-strath, and the Mitchell-Pennyroyal surface is older than or contemporary with karst development. The Horse Cave Member, Lost River Chert Bed, and Corydon Chert Member extend from Warren County, Kentucky, to Lawrence County, Indiana.

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