How many different Devonian fossils are at the Falls of the Ohio, (Indiana & Kentucky, U.S.A.)?
by Alan Goldstein Interpretive Naturalist Falls of the Ohio State Park
The Falls of the Ohio at Clarksville, Indiana and Louisville, Kentucky are world-renown for the incredible number and variety of fossils that have been found. Fossils may be seen today, when river conditions allow. Collecting is no longer permitted, because over the last 200 years, enormous tonnage's of fossils have been hauled away. We must preserve what remains for the enjoyment of generations to come.
Geologists describe the fossils in various layers or strata at the Falls. The entire rock formation is called the Jeffersonville Limestone, named from exposures at the Falls closer to that southern Indiana town (Kindle, 1899) that are no longer exposed. The individual strata (or zones) are named for their fossil content.
Actually, the lowest fossil bed exposed during very low water conditions is the Silurian Louisville Limestone, some 30 million years older than the overlying Jeffersonville Limestone. In addition, there are large amounts of Ordovician limestone ripped from the floor and banks of the Ohio River upstream. These add several hundred additional species to the faunal list, but will not be described here.
The lowest Devonian fossil layer is the coral zone. It is actually subdivided into the lower and upper coral zone. That significance is probably only appreciated by paleontologists. The lower coral zone is the uppermost Lower Devonian (Emsian stage) and the upper coral zone is lowermost Middle Devonian (Eifelian stage)! These layers are submerged most of the year (unless there is an drought in the eastern U.S.).
Above the coral zone is the Amphipora zone, named for a spaghetti-like stromatoporoid sponge that is abundant in that layer. This layer is best observed on the small cliffs on the river bank that contain numerous small grottoes.
The Paraspirifer acuminatus zone is the next layer. The lowest part is sometimes called the Brevispirifer gregarious subzone because of the millions of brachiopod shells that make up a layer in this unit. Above it is the Bryozoan- Brachiopod subzone, dominated by fossils of those phyla. The top strata of the Jeffersonville Limestone may be called the Upper P. acuminatus subzone, where this robust brachiopod may be found in the greatest abundance. This top layer is scarcely exposed at the Falls today. The Speed Limestone, named after exposures at the Essroc Cement Quarry in Speed, Indiana is Eifelian. It pinches out north of the Falls of the Ohio.
Rock from the younger Middle Devonian North Vernon (Sellersburg) Limestone (which includes the Silver Creek and Beechwood Members) are no longer found in the Park. The shaley Silver Creek Member is not exposed at the Falls are Eifelian. The Beechwood Member (Givetian stage) can be found on the western edge of Goose Island, still part of the Falls of the Ohio National Wildlife Conservation Area and protected from collecting. Counts should be considered conservative. Further study will most likely reveal additional species.
The faunal lists were drafted from the sources at the end of the article. Some additions have been made through my own personal research of the fauna of these formations over the past 15 years.
Jeffersonville Limestone Fauna (Emsian - Eifelian Age)
Phylum Species
Foraminifera 10 Arthropoda 58 Ostracoda 31 Trilobita 27 Brachiopoda 67 Bryozoa 92 Cnidarids (Corals) 160 Echinodermata 26 Blastoidea 6 Crinoidea 20 Graptozoa (Graptolites) 1 Mollusca 94 Cephalopoda 8 Gastropoda (Snails) 53 Pelecypoda (Clams) 30 Pteropoda (Sea Butterflies) 2 Porifera / Stromatoporoidea 20 Vertebrata (Fish) 3 (Need more research) Plants (Algae) 1
Total: 531
Sellersburg or North Vernon Limestone (Eifelian - Givetian Age)
Foraminifera 13 Arthropoda 7 Ostrocoda 1 Trilobita 6 Brachiopoda 45 Bryozoa Unknown Cnidaria 53 Echinodermata 40 Blastoidea 2 Crinoidea 38 Mollusca 73 Cephalopoda 13 Gastropoda 34 Pelecypoda 23 Pteropoda 3 Porifera / Stromatoporoidea 2 (Needs more research) Vertebrata Unknown
Total: 233+
Obviously, much work remains in terms of gathering lists together from the wide variety of sources of previously published studies. As we establish a reference collection at the Interpretive Center, we will acquire additional publications and within time, fill in the blanks. Faunal studies by paleontologists are largely a thing of the past. Like most sciences, paleontology consists of specialists - those studying a small part of the “big picture.” We hope to carry this general faunal research as part of the educational mission at the Park.
One would think that everything would have been “studied out” at the Falls. This is not the case. There are discoveries yet to be made. We will try to keep you abreast in our efforts to preserve - and understand to wondrous history of the rocks at the Falls of the Ohio.
Important References
Butts, Charles, 1915, Geology and mineral resources of Jefferson County, Kentucky: Kentucky Geological Survey, ser. 4, v. 3, pt. 2, 270 p. Jillson, W. R., 1931, Paleontology of Kentucky: Kentucky Geological Survey, ser. 6, v. 36, 469 p. Kindle, E. M., 1899, The Devonian and lower Carboniferous faunas of southern Indiana and central Kentucky: Bulletins of American Paleontology, v. 3, no. 12, p. 131-239. ------ 1901, The Devonian fossils and stratigraphy of Indiana: Ind. Dept. Geol. and Nat. Resources, Annual Report 25, p. 529-758, 773 - 775, 33 pls. Stumm, E. C., 1964, Silurian and Devonian corals of the Falls of the Ohio: Geological Society of America Memoirs, v. 93, 184 p.
Created December 30, 2010
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