MSU Earthcache EarthCache
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The Cretaceous outcrop is easily accessed from a large parking lot on Mississippi State University’s main campus in Mississippi State, MS. Although weathered portions of the outcrop may require minimal climbing, this site is easily accessible to most.
An ancient sea covered the campus of Mississippi State University over 70 million years ago, during the Cretaceous Period of the Mesozoic Era. The fossils that are exposed in the chalk lived—and died—in the shallow sea, and are now preserved in the chalk. They are now weathering out of the outcrop, and fossil enthusiasts check the area after a soaking rain.
The entire campus of Mississippi State University is underlain by chalk limestone. This is the Prairie Bluff formation, and it consists of both chalk and a sandy chalk. Decades ago, another outcrop located closer to Department of Geology and Geography was used as an outdoor geology laboratory for students to study fossils and weathering. (see Figure of Harned outcrop). Can you find this site on the MSU campus?
Visiting elementary students have often found oyster and clam shells, gastropods, shark teeth, and bryozoans in the outcrop.
Although every animal phylum is represented by the fossils, some of the most common specimens include mollusks. The Cretaceous oysters, Exogyra, are quite common. Exogyra evolved in the Jurassic Period, and survived through the Cretaceous Period. They are now extinct. (see Figure of Exogyra) Do you think all Exogyra in this outcrop belong to the same species?
Search the area for gastropods. Often, both planispiral (coiling in a plane) and trochospiral (coiling in a “cone”) gastropods are found in this area. Do these fossils represent the original shells of the gastropods? How can you tell? What characteristics could you look for to determine whether the 1) original material is preserved; 2) the original material has been replaced or supplemented by minerals; or 3) the original shell has been dissolved away, leaving a mold of the internal part of the shell that was filled with sediments?
If you are visiting during normal university hours, you may want to investigate further in the Dunn-Seiler Museum in the Department of Geosciences (see Figure of DunnSeiler Museum), which houses several Cretaceous fossils (see Figure inside DunnSeiler Museum), and more specifically, several examples of Exogyra (Insert Figure of DunnSeiler Cretaceous oysters). What type of Exogyra fossils did you observe at the outcrop? Can you find other examples of Cretaceous fossils from the Prairie Bluff chalk in the museum that you observed at the outcrop?
This website contains Cretaceous Pelecypods: (visit link) Scroll down to Suborder Orsteina, Superfamily Exogyrinae, and check out some of the photos of the different Exogyra species. Please note that the list of where these fossils are found is NOT inclusive.
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