Designated as a National Natural Landmark in 1966 the fossil beds extend into Jefferson County, Kentucky. The Ohio Coral Reef is a classic example of a Silurian and Devonian coral community. The site is the type locality for a number of coral species and nearly 900 nominal species have been founded on specimens collected here. Ownership: State.
A coral reef, between 395 and 345 million years old stretches from Louisville, Kentucky to Indianapolis, Indiana. 220 acres of this reef is exposed in The Falls of the Ohio National Park. Five distinct layers have been exposed. The uppermost contains fossils of brachiopods, trilobites and corals. The second layer contains an abundance of crinoid stems. The next layer contains brachiopods, sea snails and corals. The next layer contains stromotoporoids (sponge-like creatures) and branching corals. The oldest layer contains an abundance of corals.
The plaque that is attached to the visitors’ center reads:
“Falls of the Ohio Fossil Beds has been designated a National Natural Landmark. This site possesses exceptional value as an illustration of the Nation’s Natural Heritage and contributes to a better understanding of the environment. 1966 National Park Service United States Department of the Interior.”
Falls of the Ohio Fossil Beds is one of the most amazing Devonian fossil sites in the world. Within the Falls of the Ohio State Park, visitors can see the traces of life left in a gigantic coral reef that stretches from Louisville north to Indianapolis and represents deposition spanning some 45 million years. It has one of the highest species diversities known from a single locality in the Devonian (about 600 species of which 2/3rds are "type" specimens, or species discovered and recorded there for the first time anywhere in the world. It is one of the best-preserved and most accessible Devonian fossil beds (coral-stromatoporoid bioherm) in the world. An average of 500,000 visitors annually visit the park.
The interpretive center traces millions of years of history along the Ohio River and in Louisville and Southern Indiana. The interpretive center''s timeline commences 386 million years ago with what became the 100-acre fossil bed located just outside its door – one of the most extensive naturally exposed fossil beds in the world.
Visitors to the interpretive center will find a museum on the rich history of Louisville and Southern Indiana. Exhibits on everything from the area’s millions of years as an ocean bed with a coral reef to the Native American experience before the Europeans arrived to the area’s heyday as a frontier outpost and riverboat port are sure to delight both history buffs and the simply curious.
The museum boasts a reproduction of the cabin that General George Rogers Clark built in Clarksville in 1803. It was from there in 1803 that Clark's brother, William Clark, and Meriwether Lewis set off with the Corps of Discovery on the expedition across the continental United States.
For those interested in fossils, the best time to visit the state park is between August and October, when the river level is low. Removing any of the fossils is strictly prohibited.
The State Park is open every day from dawn until dusk. The interpretative center is open 9 a.m. to 5 p.m., Monday through Saturday, and 1 to 5 p.m. Sunday.
Quick examination of exposed fossils at the Falls of the Ohio River near Louisville, Kentucky reveals that local geography and climate were much different during the Devonian Period than they are today. The fossils are of organisms from a coral reef, and they are made of limestone, a type of sedimentary rock that only forms in marine environments. Limestone and coral indicate that this land must have been under salt water when the organisms lived, died, and were buried in sediment.
Additionally, coral grows poorly in cool water, so it never forms reefs more than 27 degrees in latitude from the equator. This suggests that the land where the Falls of the Ohio is now, at 38 degrees north of the equator, is further north than it was when the reef formed. Other evidence suggests that the land was actually about 20 degrees south of the equator when the reef grew, so the land has moved 4,000 miles northward since the reef formed!
More environmental information can be gleaned from a closer examination of the fossil bed. Many of the coral fossils are upside down, and this tells us that perhaps strong currents, associated with hurricane conditions, tossed the heavy corals before they were buried in sediment. If we accept this explanation, we observe that waves this strong only occur in shallow water, so the warm sea that covered what is now the Falls of the Ohio would have been shallow.
Hundreds of fossilized species have been identified at the Falls, which indicates that this sea must have had a rich variety of marine life! Many of the fossils bear similarities to animals that live in the ocean today.
During the millions of years between the formation of the ancient coral reefs and today, many slow changes occurred. Calcium carbonate precipitated out of the water, steadily burying layer after layer of skeletons on the sea floor. Newer layers above compressed older layers below, gradually cementing sediment into limestone rock. Continents moved, the sea receded, and climate changed. Deposition and erosion alternated as the dominant crust-shaping activity in the region. Several ice ages brought glaciers stretching from Canada to Indiana, just north of the Falls. Between ice ages, the glaciers retreated and the resulting melt water carved out the Ohio River Valley. Erosion eventually removed an estimated 100 feet of glacial outwash deposits and 20 feet of limestone, finally exposing the fossil bed ledges that now form the Falls of the Ohio.
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