Southeastern Section - 66th Annual Meeting - 2017

Paper No. 32-9
Presentation Time: 1:00 PM-5:00 PM


GIBSON, Michael A., Department of Agriculture, Geosciences, and Natural Resources, The University of Tennessee at Martin, 256 Brehm Hall, Martin, TN 38238, RHENBERG, Elizabeth C., Geology, Earlham College, Richmond, IN 47374 and GIBSON, Brandt M., Earth and Environmental Sciences, Vanderbilt University, 5726 Stevenson Center, 7th floor, Nashville, TN 37240,

There are three fossiliferous chert gravel occurrences in West Tennessee. Stratigraphically oldest, the Tuscaloosa (Late Cretaceous) gravels occur in isolated small remnants across the Western Highland Rim and are best exposed in northeast Mississippi, northwest Alabama, and southcentral Tennessee. Stratigraphically younger Pg/Ng (?) gravels, often referred to as “Lafayette” gravel or “continental deposits”, occur in abundance near Paris Landing, Henry Co. Finally, Tennessee River terrace gravels (Pg/Ng) are exposed in Hardin and McNairy counties near the Tennessee-Mississippi state line and in southwest Tennessee. These chert gravels are commonly fossiliferous containing partial molds of pelmatozoan echinoderms (moslty columnals), brachiopods, bryozoans, trilobites, cephalopods, and gastropods that are all of middle Paleozoic age. Usually preservation is too poor to identify cherty fossils to biostratigraphically useful genera or species, but several previous studies have concluded that these cherts are reworked from Upper Silurian through Mississippian age strata, with most of the chert gravels derived from the Devonian Camden Chert or Mississippian Fort Payne Chert. Here we report a broken chert cobble from the Pg/Ng gravel deposits near Paris, TN with a remarkably preserved Rhaphanocrinus cf. subnodosus crinoid. The specimen is preserved in profile view showing the relief details of the upper stem, entire calyx and crown with arms and pinnules in closed position. The same separation plane in the cobble preserves a wrinkled fenestrate bryozoan impression. R. subnodosus is typically an Ordovician (Trenton) crinoid genus, and as such, this is the first record of R. subnodosus in Tennessee and the first confirmed Ordovician crinoid from gravel deposits in West Tennessee.