Geologist to explore fossil bed

Earlier this week, the author made a surprise discovery while exploring low-water sites in Bayou Bartholomew: An exposed area of rock containing what appear to be fossilized clam shells. 

Fossilized shells -- possibly dating back to the time when a shallow sea covered Louisiana -- have been exposed in a rocky outcropping on the bank of Bayou Bartholomew near Bastrop [Credit: Wes Helbling]

Native fossil finds are somewhat rare in Louisiana. The more common types of fossils are small impressions of marine creatures in gravel that has traveled to the state from other parts of the country. 

Dr. Gary Stringer, professor of geosciences at the University of Louisiana at Monroe, said photos from bayou site are “extremely interesting” because the fossils seem to pre-date the known geological surface of this area. 

“The general surface geologic map indicates mainly very young geological formations, probably less than two million years old, in Morehouse Parish,” he said. “The fossils that you have appear to be much older and marine in origin.” 

Most of the fossils in the rocky outcropping are mold fossils, or impressions left by prehistoric creatures. There are also a few cast fossils, or three-dimensional shell shapes created by minerals filling in the impressions. 

Stringer said one of the cast fossils looks very similar to a marine clam called Venericardia. 

“It is commonly found in the Eocene, which is 30 to 45 million years old,” he said. “My first thought would be that the bayou has eroded through the younger material and is exposing older material.” 

He said the fossils may belong to the Claiborne Group, a geological formation which has exposures in nearby Union Parish. 

Stringer plans to visit the site in the near future to determine the fossils’ age, and whether or not they are actually marine. 

Fossils from the prehistoric sea that once covered Louisiana are rare, but they have turned up in other parts of the state. 

The Copenhagen Hills Preserve in Caldwell Parish is known to contain fossil-rich marine sediments dating back about 38 million years. 

According to the Ouachita River Foundation, fossilized sea beds containing thousands of seashells were documented in the river before dam construction raised the water level above them. 

Fossil hunting is not recommended in Bayou Bartholomew. In addition to the dangerous summer heat, the bayou banks are home to poison ivy, venomous snakes and biting insects. 

Author: Wes Helbling | Source: Bastrop Daily Enterprise [July 10, 2011]