GEOLOGICAL AND STATISTICAL ATTRIBUTES OF TWO ECHINODERM-BEARING FAUNAS FROM THE UPPER MISSISSIPPIAN (CHESTERIAN) RAMEY CREEK MEMBER, SLADE FORMATION, EASTERN KENTUCKY, U.S.A

Well-preserved echinoderm faunas are rare in the fossil record, and hence, to further our understanding of them, faunas from two localities in the shallow open-marine Ramey Creek Member, Slade Formation, of eastern Kentucky were examined. Though time-equivalent, the localities (Valley Stone and 213 quarries) are separated by 80 km across the paleo-Kentucky River Fault Zone, which apparently controlled regional deposition at the time.

To understand the attributes of both localities, geologic and structural settings, lithofacies, and the faunal makeup and abundances (diversity, evenness, density), were compared. Of more than 5000 fossil specimens from both localities, 9–34% were echinoderms from 3–5 classes. Nine non-echinoderm classes were present at both localities. Due to large numbers of specimens, statistical methods were used to evaluate community richness, diversity, evenness and density. The α-diversity of the 213 and Valley Stone quarries was 45 and 65, respectively, but the β-diversity, or change in species between localities, was 44. The total diversity across the entire eastern Kentucky area (γ-diversity) was 77 species.

Faunas from the Valley Stone Quarry grew in an extensive, uplifted, platformal setting in four distinct lithofacies (environments), which accommodated greater richness and diversity, even though organism densities and abundances were less. In contrast, fauna from the 213 Quarry grew in a localized, deeper, storm-shelf setting on the downdropped side of the fault zone, characterized by a single lithofacies with higher densities and lower diversity. Though the faunas were originally collected as “crinoid gardens,” community analyses indicate that echinoderms were only minor to modest constituents of both communities, while bryozoans, brachiopod and sponges were far more abundant. In effect, 213 Quarry communities were “bryozoan thickets” and Valley Stone communities were “brachiopod pavements.” Most echinoderms were probably present in response to ambient energy regimes, but higher-level bafflers may have enhanced conditions for lower-level feeders. Although storm events likely preserved the communities, community makeup appears to have been largely controlled by depth and energy levels that were probably related to regional structural controls.