Year of Publication

2018

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department

Earth and Environmental Sciences (Geology)

First Advisor

Dr. Frank R. Ettensohn

Abstract

Well-preserved echinoderm faunas are rare in the fossil record, and when uncovered, understanding their occurrence can be useful in interpreting other faunas. In this study, two such faunas of the same age from separate localities in the shallow-marine Ramey Creek Member of the Slade Formation in the Upper Mississippian (Chesterian) rocks of eastern Kentucky are examined. Of the more than 5,000 fossil specimens from both localities, only 9–34 percent were echinoderms from 3–5 classes. Nine non-echinoderm (8 invertebrate and one vertebrate) classes occurred at both localities, but of these, bryozoans, brachiopods and sponges dominated. To understand the attributes of both localities (Valley Stone and 213 quarries), the geologic and structural settings, lithofacies and depositional environments, as well as faunal makeup and abundances (diversity, evenness, density), were compared and contrasted. Faunas from the Valley Stone Quarry were located on an uplifted fault block in more shallow, open-marine waters with higher energies. As indicated by four distinct lithofacies, the depositional setting was more extensive and varied with interspersed shoals and basins that could accommodate a greater richness (65 species), even though organism densities and abundance were less. In contrast, fauna from the 213 Quarry were located on a downdropped fault block in a more localized, deeper, storm-shelf setting, characterized by a single lithofacies. Although organism density and abundance were nearly twice as high as that at the Valley Stone Quarry, species richness was lower (45 species), and only one species, a bryozoan, predominated. Overall, echinoderm classes, species and individuals were more abundant at the Valley Stone Quarry, and I suggest that this is related to the shallower and more varied depositional environments that developed in response to presence on the shallow, uplifted fault block. This suggests the importance of regional features like faults in controlling environments and organism distribution through time. Although the faunas were originally collected for their echinoderm-dominated “crinoid gardens,” in fact, echinoderms were in the minority, and bryozoans and brachiopods predominated in the communities. Hence, the communities might better be described as bryozoan “thickets” and brachiopod “pavements.”

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2018.361

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