FAUNA FROM A WAULSORTIAN-LIKE MOUND IN THE FORT PAYNE FORMATION (LOWER MISSISSIPPIAN) OF TENNESSEE

A new road cut along TN-52 has exposed a Waulsortian-like mound just east of Celina, TN at the base of the Fort Payne Formation. The exposed part of the mound is approximately 19m in height and 50m in width. At the west end of the outcrop the mound overlies some 15cm of non-fossiliferous, gray-green shale with phosphate nodules interpreted to represent the Maury Shale of Kinderhookian age. The Maury is in sharp contact with the underlying Chattanooga Shale. The mound is composed of three distinct geometric bodies. The lowest body is a geometrically complex shale unit with three distinct crests and flanks that apparently pinch out laterally into shale of the Maury. The middle body is a complex of several carbonate beds that pinch and swell over the lower clastic body, and thin laterally to the west into two thin (7cm and 23 cm) off mound carbonate beds. The upper mound body is fine-grained, greenish-gray shale that comprises about 50 percent of the total mound thickness. It is thickest over the middle of the mound and thins away from the mound crest to the east and west where the outcrop ends.

The lower and upper clastic bodies have yielded a diverse fauna that includes articulate brachiopods, cryptostome bryozoans, fenestrate bryozoans, crinoids, bivalves, possible sponge spicules, trilobites, ostracodes, and solitary rugose corals, approximately in decreasing order of abundance. Cephalons and pygidia from the trilobites so far recovered belong to a single species of the genus Australosutura. The presence of Australosutura is important because it is a cosmopolitan genus that has been reported from Australia, Argentina, Belgium and both western and central United States.

Previous authors have interpreted Australosutura to represent off-shelf, deep water marine environments. Cryptostome bryozoans have also been strongly associated with the deeper end of European Waulsortian phases by Lees. These both support an interpretation of relatively deep water environments for the Tennessee mound.