Southeast of Kosciusko, around milepost 161 of the Natchez Trace Parkway, the road runs along hills of Winona greensand under a cap of Zilpha clay, the two mapped together on the state's 2006 geologic map of the Kosciusko quadrangle. The Winona is a marine sand rich in glauconite, a green mineral bearing iron and potassium, and it takes its name from exposures at Winona in Montgomery County. Fresh, it is gray to green. At the surface it weathers to a rusty red-brown or dark brick red, with knobby, contorted ledges of limonitic sandstone and sandy ironstone, often holding the molds of shells.
The top of the Winona is a line geologists have long leaned on. Over much of Attala County it is marked by a ledge of knobby ironstone, usually two or three feet thick and commonly full of fossil molds, and the contact shows plainly on well logs. Oil companies mapped on a glauconite bed about thirty feet higher and called it the top Tallahatta. The 1963 state survey of the county named the lowest part of the Zilpha the Zama member, after a small village in southeastern Attala County.
Thicknesses vary. The 1963 survey measured the Winona at 15 to 35 feet in the county's outcrop; the 2006 quadrangle map gives about 60 feet around Kosciusko and the Zilpha anywhere from a few feet to 140. On the Winona the land forms a cuesta of broad, flat-topped ridges. The Zilpha clays yield little groundwater, and some small streams draining them south of Kosciusko, east of the Yockanookany River, dry up in long droughts. Elsewhere the Winona has yielded shellfish, snails, sea urchins, crabs and shark teeth, but a 2007 Park Service paleontological inventory knew of none from parkway land.
Getting there
33.0466, -89.5699
Locations are approximate and may be inaccurate, on private land, or otherwise inaccessible. Check before you travel.
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