A COMPARATIVE STUDY OF THE FALLS OF THE OHIO DEVONIAN CORAL ZONE BIOSTROME TO REEF-LIKE PALEOCOMMUNITIES THROUGH TIME

Preserved coral reefs and reef-like faunal assemblages can demonstrate complex ecological relationships that are often difficult to observe in other types of fossil deposits. These framework-building assemblages appear repeatedly through geologic time and show dynamic relationships between marine organisms. Examining the way that these communities change over time can reveal how ecological associations evolve through the Phanerozoic. The purpose of this study is to build upon our previous work by comparing the community structure of the Middle Devonian coral assemblages at the Falls of the Ohio State Park to other preserved Devonian reefs assemblages as well as comparable kinds of deposits both before and after the Devonian.

Located in southern Indiana, the Falls of the Ohio State Park is world-renowned for limestone beds that contain diverse and well-preserved coral assemblages. These beds make up what is known as the Jeffersonville Limestone and are approximately 419.2-389 million years in age. This ongoing research effort focuses on the lowest biostratigraphic horizon, known as the Coral Zone. In our previous study, a total of 963 specimens of tabulate corals, rugose corals, and stromatoporoids were identified and measured. The taxa found in this horizon exhibited a wide range of body sizes, and this suggests that these assemblages contain multiple generations of organisms. Despite being ecologically diverse with respect to coral taxa, aside from corals and stromatoporoids, no other faunal elements were observed. Additionally, these organisms did not exhibit evidence of bioerosion, interactions between organisms or intergrowth between corals and the horizon was lacking a three-dimensional framework of preserved organisms. This suggests the horizon is a biostrome, and should not be referred to as a reef.

In this study, we continue this work by comparing the assemblages of coral to similar paleocommunities before, during and after the middle Devonian in other locations around the world. Specifically, we examine whether the lack of interactions/intergrowth between organisms and the lack of a three dimensional framework found at the Falls of the Ohio State Park is typical for coral assemblages of the mid-Paleozoic, and evaluate whether this well-known assemblage is truly as unique as it is perceived to be.