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Date Available

8-25-2026

Year of Publication

2026

Document Type

Thesis

Degree Name

Master of Science (MS)

College

Arts and Sciences

Department/School/Program

Geology

Faculty

Frank Ettensohn

Abstract

The Strodes Creek Member of the Lexington Limestone is a small, unusual member that is largely known for its beds of fragmented and overturned stromatoporoids. The Strodes Creek Member occurs as two distinct stratigraphic bodies, wholly encompassed by the Millersburg Member, which represents a shallow, open-marine, mixed-clastic-carbonate platform, characterized by thin-bedded to nodular, fossiliferous calcarenites and calcirudites interbedded with shale. In contrast to the Millersburg, the Strodes Creek exhibits a lithologic background of dark, organic-rich, calcareous shales with a westward-thickening section of very irregularly bedded, stromatoporoid-rich, fossiliferous calcisiltites (packstones and wackestones). The calcisiltites are commonly associated with hummocky crossbedding, pinch-and-swell bedding and gutter casts Three intervals of beds with fragmented stromatoporoids are thicker in the western part of the southern area along a fault-bounded margin. More distal to the faults in northern and eastern parts of the southern area and in most of the northern area, Strodes Creek beds become thinner, more even-bedded, and contain fewer stromatoporoids. Stromatoporoid-bearing limestones are separated by thin beds of dark, organic-rich shale with common Sphenothallus.

The Strodes Creek is interpreted to represent relatively deeper-water basinal environments than the surrounding Millersburg Member. The dark color of the shales and common Sphenothallus suggest relatively deeper water than the surrounding gray shales of the Millersburg Member.  The beds of fragmented, overturned stromatoporoids in the Strodes Creek, represent lobes of storm debris transported from shallower Millersburg platform environments and dumped into the local deeper-water basinal settings. Because (1) the southern and western parts of the Strodes Creek bodies are fault-bound, (2) faults separate the southern and northern areas, and (3) the stromatoporoid-fragment intervals thicken toward the southern and western faults, growth faulting is inferred to have down-dropped the two areas, resulting in deeper-water, basinal conditions, unlike those on the surrounding Millersburg platform.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2026.452

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