Abstract

A single broadly exposed bedding surface in the coral zone of the Middle Devonian Jeffersonville Limestone at the Falls of the Ohio, Kentucky and Indiana, displays a virtually in situ contemporary population of colonial corals and Stromatoporoids. The positions, sizes, shapes, orientations, and subfamilial or generic identities of 14,233 unbroken colonial coelenterates were recorded by detailed quadrat mapping of the bedding surface.

The colonial coelenterate fauna (exclusive of branching Favositinae) consists of 70.8 per cent tabulate corals, 25.5 per cent Stromatoporoids, and 3.7 per cent compound rugose corals. These coexisted with numerous solitary rugose corals and pelmatozoans. Stromatoporoids and some tabulate corals concentrated in north–south linear bands in response to ecological conditions, whereas colonial rugose corals were apparently randomly distributed Concentrations of branching Favositinae fragments mark the growth-sites of large colonies. Significant positive and negative linear correlations of paired taxonomic groups indicate tendencies of preferred distribution and concentration among numerically abundant groups.

The preferred orientation of the long axes and distal ends of recumbent elongate and massive corals is east–west. Combined evidence suggests that a gentle east–west tidal current, with a stronger easterly component, was responsible for the orientation. The distribution of colonies in the Devonian biostrome is in some ways analogous to the distribution patterns of modern non-reef corals on the South Florida carbonate platform.

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