A HISTORY AND CENSUS REPORT FROM TWO LATE MISSISSIPPIAN BRYOZOAN/ECHINODERM FAUNULES, POWELL COUNTY, EAST-CENTRAL KENTUCKY

Mississippian echinoderms are well-known and widespread, but there are few studies that attempt to do detailed census studies of the given community. A complete bryozoan/echinoderm “garden” was collected form the shallow, open-marine, Ramey Creek Member (Chester, Hombergian) of the Slade Formation on the western margin of the Cumberland Plateau in east-central Kentucky. The entire garden was collected in 87 slabs with a combined area of about 35 ft² (3.3 m²).

Development of the garden suggests that the area was first disrupted by storm/seismic event that resulted in filled scours on which an initial garden was established. A later storm event destroyed this garden and buried it beneath a thin layer of skeletal sand. A second garden was established on top of the new sands, was later leveled in a storm, was exposed for a brief period and subsequently buried in a mud fall-out distal to yet another storm. Hence, the gardens are typically preserved on the bottoms and tops of the same slabs.

Detailed preservation of Archimedes fronds and some of the delicate crinoids indicate that specimen transportation was not far and final burial occurred within a few weeks of garden destruction. The garden was clearly dominated by a thicket-like development of Archimedes bryozoans, which were lower- to mid-level suspension feeders, out of which higher-level crinoid and blastoid suspension feeders apparently projected. Lower-level suspension feeders included smaller encrusting, ramose and fenestrate bryozoans, six species of brachiopods and rare Sphenophallus. Coral passive predators and deposit feeding echinoids were also present but rarer. Even shark teeth are found in the garden indicating their presence in the waters above. Although preliminary, we will present a census population analysis that details the relative abundance, diversity and trophic levels of the more than 25 species that inhabited the garden. This may provide a basis for detailed comparison with other Mississippian bryozoan/crinoid gardens.