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PALEONTOLOGY ARTICLE
Upper Cretaceous Fossils of Frankstown, Mississippi
by MIKE BALDWIN
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07.12.2007: Once or twice a year MAGS members travel to
Frankstown, Mississippi to search for sharks' teeth and
other vertebrate fossils in the streambed clay of Twenty
Mile Creek.
During the summer of 1990, construction on Highway 45,
about seven miles south of Booneville, Prentiss County,
in northeastern Mississippi revealed two concentrated
fossil beds. One contained an abundance of sharks' teeth
and the other an abundance of oyster shells.
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The fossils in the Frankstown creekbed are about 75 million
years old. These fossils come from the base of the Demopolis
Formation, just above the Coffee Sand. The Coffee Sand can be
seen in the exposure along Twenty Mile Creek near where
Highway 45 crosses it. One interesting aspect of the Coffee
Sand is the large boulder-sized concretions that are scattered
along the creekbed. I took the picture above on a recent visit
to Frankstown. After many visits to this location, I am still
fascinated by these structures. Concretions are rounded masses
of rock that formed by the cementation of sediments where lime
or silica is concentrated in certain layers of ground water.
Though the Coffee Sand concretions of Twenty Mile Creek are
boulder-like in size and shape, they were not rounded by being
rolled along the river bottom but acquired their rounded shape
by cementation in place within the formation.
Many fossils from the Frankstown site are fromgroups of
animals that died out in a great extinction at the end of the
Mesozoic, indicating that the site is no younger than the
Cretaceous Period. These animals include the oyster Exogyra,
ammonites, some of the sharks (Hybodus, Squalicorax), some of
the rays (the sclerorhynchid sawfish), some of the bony
fishes, the mosasaurs and the dinosaurs.
The cause of the great extinction at the end of the Cretaceous
is believed to have been an asteroid impact which spread a
layer of soot across the earth, filling the atmosphere,
blocking sunlight and causing plants and the animals that
depended on them to die. One interesting detail of the great
extinction is that not everything died. Gars, turtles,
crocodiles, opossums and many others lived on as if nothing
had ever happened.
A partial list of fossils found at the Frankstown site
include: formaminifera, sponge, arthropod (ostracod,
crustaceans), mollusks (oysters, jingel shells, scallop,
gastropod, scaphopod), annelid worms, brachiopod, bryozoan,
more than 12 varieties of shark, rays, bony fish, turtles,
mosasaur, crocodiles, and dinosaurs (theropod, hadrosaurid);
microfossils and trace fossils.
SOURCE: Earl Manning and David dockery. A Guide to the
Frankstown Vertebrate Fossil Locality (Upper Cretaceoous),
Prentiss County, Mississippi. Circular 4; Mississippi
Department of Environmental Quality. Office of Geology.
Jackson, Mississippi. 1992.
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