South of Dicks Creek, near milepost 238 of the Natchez Trace Parkway, the motor road climbs off the Ripley Formation onto the Prairie Bluff Chalk, the last Cretaceous formation along this stretch of the parkway, and follows it along the ridge toward Witch Dance. The 2023 Office of Geology map of the Houston East quadrangle describes it as blue to gray clay marl with beds of chalk, very fossiliferous, with phosphatic molds at its base, up to about 90 feet thick and resting on an erosion surface cut into the Ripley. It settled on a broad, shallow shelf about 50 to 100 meters deep.
In a 2021 study, researchers sampling a 6.5 meter section at a landfill in Chickasaw County found marl and chalk alternating in beds up to about a meter thick, and traced the rhythm to precession, the roughly 20,000 year wobble of Earth's axis. They correlated the beds at the precession scale with the end-Cretaceous succession near Morello, Italy. The section belongs to the Discoscaphites minardi and D. iris ammonite zones of the latest Maastrichtian.
In neighboring Pontotoc County a 1943 survey listed ammonites, nautiloids, sea urchins, oysters, shark teeth and mosasaur remains, including tooth sockets, from the formation. The Houston East map notes sand, sandstone and sandy marl near the top of the unit in the north, thickening to the north and northwest.
Getting there
33.9689, -88.9296
Locations are approximate and may be inaccurate, on private land, or otherwise inaccessible. Check before you travel.
Hear it from the road
Whistlestop is an audio tour guide app that tells you this story automatically when you drive past. No searching, no tapping, nothing to ask.
