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The Otter Creek coral bed is a gray medium-grained limestone of Late Ordovician (Richmond) age on the east flank of the Cincinnati arch in Kentucky. The coral bed is lithologicaily transitional with the grayish-green finegrained muddy dolomite of the underlying Rowland Member of the Drakes Formation, and is intercalated with and conformably overlain by dark-yellowishorange fineto coarse-grained dolomite of the Preachersville Member of the same formation. Where present, the Otter Creek is considered the basal unit of the Preachersville. The most abundant fossils in the Otter Creek coral bed are the corals Calapoecia hnronensis, Foerstepliyttum vacuum, Grcwingkia rustica, and Tetradium approximatitm. The stromatoporoid Aulacera cylindrica and brachiopods of the genera Hcbertella and Platystropliia also are common. The'se fossils and others are widespread in these beds on the east side of the Cincinnati arch and were identified in seven collections from the Richmond North, Union City, Palmer, and Lancaster quadrangles, Kentucky. Upper Ordovician coral beds containing similar faunas occur on the west side of the Cincinnati arch, but their relation to the Otter Creek coral bed is uncertain. Systematic annotations of the corals and stromatoporoids in the Otter Creek coral bed are included. INTRODUCTION The Otter Creek coral bed is a useful stratigraphic marker at the base of the Preachersville Member of the Drakes Formation (Upper Ordovician); it separates the Preachersville from the underlying Rowland Member of the Drakes Formation in parts of southeast central Kentucky (Weir and others, 1965, p. 18). The Otter Creek is stratigraphically important because it contains the only wellpreserved fauna that has been recognized in the Drakes Formation on the east side of the Cincinnati arch, and because it is one of several similar beds in Upper Ordovician rocks of the KentuckyOhio-Indiana region. The Otter Creek coral bed has been mapped in the Richmond North, Union City, and Palmer quadrangles (unpub. data) as part of the U.S. Geological Survey mapping program in Fl F2 CONTRIBUTIONS TO STRATIGRAPHY cooperation with the Kentucky Geological Survey. Seven fossil collections (fig. 1), six from these three quadrangles and one from the nearby Lancaster quadrangle, provide a basis for comparing the Otter Creek with other coral beds of similar age. The field observations and collections were made by Simmons, except for collection USGS 4662-CO, which was made by G. W. Weir. The identification and study of corals and stromatoporoids were made by Oliver. STRATIGRAPHIC RELATIONS AND LITHOLOGY The Drakes Formation comprises the uppermost Ordovician strata in the area studied. It is conformably overlain by the Brassfield QUADRANGLES A, Richmond North B, Union City C, Palmer D, Lancaster

Otter Creek coral bed and its fauna, east-central Kentucky