At about milepost 247.6 the Natchez Trace Parkway leaves the floodplain of Tallabinnela Creek and climbs the east face of the Pontotoc Ridge, a ridge held up by the Ripley Formation. The 2024 Office of Geology map of the Troy Southeast quadrangle shows the motor road crossing from creek alluvium near the 340 foot contour onto Ripley beds that rise past 440 feet, with the Demopolis Chalk of the Black Prairie in the valleys to the east. The map gives the Ripley there up to about 110 feet of sand, chalk and limestone over a transitional clay at its base.
A 1943 Mississippi Geological Survey report on Pontotoc County explains the shape. The ridges are cuestas, formed as west-dipping beds of sand, chalk and limestone weather at different rates. The easternmost is held up by the lower Ripley limestone, its gentler slope is worn on the clay at the base of the Ripley, and the broad valley floor to the east lies on the Selma chalk. The report gives the ridges 450 to 550 feet of elevation, 100 to 150 feet above the chalk valleys.
In Pontotoc County the 1943 report found the Ripley mostly marine micaceous sand with lenses of chalk and limestone, up to 250 to 275 feet thick. Ledges in the west wall of Tallabinnela Creek, half a mile east of Troy, yielded oysters, the ammonite Baculites tippaensis, belemnites, crab claws and shark teeth to that survey.
Getting there
34.0985, -88.8600
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.
