The detection and importance of subtle biofacies within a single lithofacies: The Upper Ordovician Kope Formation of the Cincinnati, Ohio region

Environmental controls on. the distribution of fossils most commonly are fo und by recognizing that certain distinctive fossil assemblages are associat ed with particular lithofacies. Lack of change in lithofacies commonly is u sed as indicating a lack of significant environmental effects on the strati graphic distribution of fossils. The results presented here challenge that view. The Upper Ordovician Kope Formation of the Cincinnati, Ohio, area has long been considered a single unit, both Lithostratigraphically and in ter ms of depositional environment. Gradient analysis of over 1000 fossil assem blages reveals subtle environmental control on the distribution of fossils, in the absence of obvious lithologic change. This gradient analysis is use d to construct an ecological model of the Kope fauna, with values of prefer red depth, depth tolerance, and peak abundance estimated for the most commo n fossils. This method, conducted within a single lithofacies, offers the p otential for reconstructing sequence architecture because faunas can be mor e sensitive recorders of environment than lithofacies. In addition, the pre sence of subtle facies control as in the Kope raises the prospect that envi ronmental controls on paleobiologic and biostratigraphic patterns may be mo re pervasive than generally acknowledged.