Devonian and Mississippian Systems

Type section: The Clegg Creek Member of the New Albany Shale was named by Lineback (1968, 1970) for exposures along a road cut on Indiana Highway 160, 2 miles (3.2 km) southeast of Henryville, Clark County (N¼E¼ lot 240, Clark's Grant). The name was taken rom a tributary to Silver Creek 2 miles (3.2 km) from the type section.

Description: The Clegg Creek Member is characterized by brownish-black to black, finely laminated pyritic shale rich in organic matter. The Clegg Creek contains the highest concentrations of organic material in the New Albany (Hasenmueller, 1982). There are a few greenish-gray shale or mudstone beds and phosphatic nodules near the top of the Clegg Creek Member.

Overlain by the Rockford Limestone, the Clegg Creek Member is about 40 feet (12 m) thick in Jackson, Scott, and Clark Counties and thins southward to 22 feet (6.7 m) in Harrison County (Hasenmueller, 1982). The Clegg Creek has not been mapped as a distinct unit in southwestern Indiana. This unit overlies the Camp Run Member of the New Albany Shale and includes the upper part of the Blackiston Formation, all of the Sanderson Formation (including the Falling Run Member), the Underwood and Henryville Formations, and the Jacobs Chapel Shale of Campbell (1946). The latter four units named are recognized as beds in the upper part of the Clegg Creek Member (Lineback, 1970). In ascending order they are (1) the Falling Run Bed - 0.2 foot (0.06 m) of ellipsoidal or spherical phosphatic nodules; (2) the Underwood Bed - 0.4 foot (0.1 m) of greenish-gray shale containing many conodonts and scolecodonts; (3) the Henryville Bed - 0.4 to 1.7 foot (0.1 to 0.5 m) of carbon-rich fissile shale containing conodonts, phosphatic brachiopods, and plants; and (4) the Jacobs Chapel Bed - greenish-gray calcareous glauconitic mudstone or shale, 0.2 to 0.6 foot (0.06 to 0.18 m) thick on outcrop.

Correlation: The Underwood Bed of the Clegg Creek bears a conodont fauna that is typical of the Siphonodella sulcata Assemblage Zone, which is Kinderhookian in age, and the Devonian-Mississippian boundary is at or just below the base of this bed. That part of the Clegg Creek Member below the Falling Run Bed is equivalent to the upper part of the Grassy Creek Shale. the Saverton Shale, and the Louisiana Limestone of Illinois (Line back, 1970). The Underwood, Henryville, and Jacobs Chapel Beds of the Clegg Creek contain conodonts indicative of the cuI division of the German standard and part of the cull division (Mississippian) and are equivalent to the Hannibal Shale of Missouri (Lineback, 1970). The Jacobs Chapel Bed correlates approximately with the middle and upper parts of the Hannibal and probably lies within the Siphonodella duplicata s.s. and the S. quadruplicata Assemblage Zones (Rexroad, 1969).

The Upper Devonian biostratigraphic marker Protosalvinia (Foerstia) is found about 20 feet (6 m) above the base of the Clegg Creek Member in southern Indiana, and on the basis of the position of Protosalvinia the Clegg Creek Member of Indiana has recently been correlated tentatively with part of the Antrim Shale of the eastern part of the Michigan Basin, the Huron Member of the Ohio Shale of Ohio and northeastern Kentucky, and the upper part of the Gassaway Member of the Chattanooga Shale in Tennessee (Hasenmueller and others, 1983).