Occurrence, Stratigraphic Distribution, and Abundance of Chitinozoa from the Middle Devonian Columbus Limestone of Ohio

Chitinozoa from the Middle Devonian Columbus Limestone of central Ohio belong to eight species of the genera Alpenachitina, Ancyrochitina, Angochitina, Conochitina, Desmochitina, and Eisenackitina. Two new species, Ancyrochitina frankeli and Eisenackitina robusta, are described. The Chitinozoa occur in carbonate rocks such as mudstone, grainstone and packstone that represent well circulated open marine conditions. They are absent from dolomite which represents sediment deposited at a shallow water depositional site characterized by restricted water circulation. Comparison of the Columbus Limestone Chitinozoa with faunas from similar Middle Devonian strata in Iowa, Illinois, and Missouri indicates that the Middle Devonian Wabash Platform, located in Indiana, effectively restricted the distribution of chitinozoans in the Illinois and Appalachian Basins. OHIO J. SCI. 76(5): 214, 1976 Chitinozoa were first described in the 193()'s by the German scientist A. Eisenack (1930, 1931) from Silurian glacial erratics in the Baltic region of Europe. Since that time interest in this group of extinct organic-walled microorganisms has grown in Europe and the Americas as exemplified by the recent monographic treatment of the group (Combaz et al, 1967; Taugourdeau et al, 1967). The interest of North American paleontologists in this group of fossils has grown steadily since the 1950's. The importance of Chitinozoa is twofold. They are abundant and easily extracted from strata of Ordovician through Devonian age and, as some of the forms may have been members of the lower Paleozoic zooplankton (Chaiffetz, 1972), their biostratigraphic value is obvious. The presence of Chitinozoa in the Columbus Limestone as well as faunas from strata of similar age elsewhere in the Midwest (Urban, 1972; Urban and Newport, 1973; Legault, 1973; Wood, 1974) suggest their potential importance for the refinement of the biostratigraphy of Middle and Upper Devonian strata in North Manuscript received January 28, 1976 and in revised form May 18, 1976 (#76-11). America. Second, Chitinozoa appear to be useful bathymetric indicators (Williams and Sarjeant, 1967; Gray et al, 1974). Laufeld (1975) has noted, in the Silurian of Gotland, Chitinozoa diversity and abundance increase away from reefoid detrital limestones in the direction of deeper water. The dominant feature of the Middle Devonian paleogeography of Indiana, Illinois, and Ohio is now recognized as consisting of a broad shallow water carbonate shelf (Droste et al, 1975). That shelf, called the Wabash Platform, controlled the sedimentology of adjacent basins in Missouri, Iowa, Illinois, Michigan, and Ohio. It must have influenced the spatial and temporal distribution of the marine plankton and members of the benthic fauna. In this regard, the description of the Columbus Limestone Chitinozoa is the necessary first step in establishing the degree of Chitinozoa faunal interchange in the Illinois, Michigan, and Appalachian Basins. The purpose of this paper is to describe the occurrence, stratigraphic distribution, and abundance of Chitinozoa in the Middle Devonian Columbus Limestone in northcentral Ohio.