Silurian System

Type section and use of name: The Lee Creek Member of the Brassfield Limestone was named by Nicoll and Rexroad (1968, p. 9) for the very dolomitic upper part of the Brassfield in southeastern Indiana and adjacent Kentucky. The type section is just below a long-abandoned road near the head of a short tributary of Lee Creek in the NE¼SE¼SE¼ sec. 36, T. 3 N., R. 9 E., Jefferson County, Ind. Two primary reference sections are along the road and above an abandoned quarry in the NW¼NE¼NE¼ sec. 31, T. 3 N., R. 10 E., and at Dog Falls on a tributary of Big Saluda Creek, center SE¼ sec. 2, T. 2 N., R. 9 E., Jefferson County, Ind.

Description: The Lee Creek Member is fine-grained dolomite that varies from tan to red brown and in places has a greenish cast. Glauconite, mostly in sand-sized grains, is common, especially near the top of the unit. Bedding is thin and tends to be irregular. Maximum measured thickness (Nicoll and Rexroad, 1968) is 4.3 feet (1.3 m), but the member is commonly less than 1 foot (0.3 m) thick. It is generally present from Mt. Washington, Bullitt County, Ky., as far north as Madison, Jefferson County, Ind. It is discontinuously present north of Madison and is recognized in Decatur and Switzerland Counties. Apparently its relation to the underlying Brassfield proper varies from unconformable to conformable. It is unconformably overlain by the Osgood (a member of the Salamonie Dolomite in Indiana and a formation in Kentucky).

Correlation: The conodont fauna of the Lee Creek Member falls mostly within the Ozarkodina celloni Assemblage Zone (Nicoll and Rexroad, 1968), which correlates with the C5 division of the Telychian Stage in the upper part of the type Llandoverian Series in Great Britain. The same conodont fauna has been reported from the middle part of the Brandon Bridge Member of the Joliet Formation of northeastern Illinois (Liebe and Rexroad, 1977), the Seventy-Six Shale Member of the Bainbridge Formation in southwestern Illinois (Satterfield and Thompson, 1975), and the top of the Noland Formation and at one locality in the base of the Estill Shale in Kentucky (Rexroad and Nicoll, 1972 Rexroad and Kleffner, 1984). This zone indicates an early Niagaran age in the North American standard.