LITHOLOGY AND PERCEPTIONS OF BIODIVERSITY: PALEOECOLOGICAL VARIATION IN THE PIONEER VALLEY MEMBER OF THE UPPER ORDOVICIAN KOPE FORMATION OF NORTHERN KENTUCKY

Lithology greatly influences the faunal composition and preservational qualities of fossil communities. The Upper Ordovician Kope Formation contains several different lithological categories, each which exhibit noticeable differences in faunal composition. Aside from studies that focus on exceptionally preserved fossils within shale deposits, most studies of diversity in the type Cincinnatian involve the more easily sampled limestone and siltstone beds. The shale horizons, often regarded as largely barren, are frequently left unsampled despite their delicately-preserved and rare faunal elements. The purpose of this study is to investigate the degree to which faunal diversity varies among limestone, siltstone and shale samples within a stratigraphically constrained interval, the Pioneer Valley member of the Kope Formation. In total, 108 bulk limestone, siltstone and shale samples were collected from four localities along the AA highway in northern Kentucky. Genus-level abundance counts were obtained and used to conduct a number of qualitative and quantitative assessments of biodiversity.

Shale samples exhibited well-preserved individuals on the surface of shale partings, often without damage or apparent transport. Brachiopods are the dominant faunal element within shale samples, particularly the genera Sowerbyella and Dalmanella. While fossils in limestone and siltstone beds are often also well preserved, there was a greater degree of disarticulation of fossil material which could be attributed to some amount of time averaging not seen in the highly laminated shale intervals. A typical assemblage within a limestone bed was notably richer and included many disarticulated crinoid columnals, trilobite thoracic segments, bryozoans and abundant fragments of Sowerbyella and Dalmanella. In addition to these qualitative assessments, a range of community-level measures of biodiversity were calculated here including richness, evenness, proportional rarity, and similarity. These measures demonstrate the amount of variation in community structure among samples associated with differences in lithology. Understanding the nature of the relationship between lithology and biodiversity will provide a clearer window into the apparent link between paleoenvironmental and paleoecological variation within the type Cincinnatian.