Mississippian System

Type section and use of name: The name Jacobs Chapel Shale was applied by Campbell (1946, p. 855-856) to less than a foot (0.3 m) of greenish plastic shale overlying black shale of the New Albany Shale and underlying the Rockford Limestone in southern Indiana. The best exposure in the area near Jacobs Chapel Church and School is about three-quarters of a mile (1.2 km) northwest of Jacobs Chapel Church in the banks of Lewis Branch on the line between lots 86 and 107, Clark's Grant, Floyd County, Ind. The Jacobs Chapel is now recognized as the uppermost bed of the Clegg Creek Member (Lineback, 1968, 1970) and of the Ellsworth Member (Hasenmueller and Bassett, 1981) of the New Albany Shale.

Description: Exposures of the Jacobs Chapel Bed have been recognized in Scott, Clark, and Floyd Counties, where its thickness is generally between 0.2 and 0.6 foot (0.06 and 0.18 m), although the bed is absent from some places. In the subsurface the bed is too thin to be recognized on most conventional geophysical logs. It has been recognized, however, in cores as far north as Marion County (Hasenmueller and Bassett, 1981) and has also been recognized in southeastern Illinois by Cluff and others (1981), who extended the use of the name Jacobs Chapel Bed into Illinois. The Jacobs Chapel is a plastic greenish to dark-green glauconitic, sparsely fossiliferous shale. It is similar to some shale beds lower in the New Albany but contains more glauconite and calcite, so that earlier the Jacobs Chapel was interpreted as a basal phase of the Rockford Limestone (for example, Huddle, 1934). The abrupt lithologic changes, however, at both the top and the bottom of the Jacobs Chapel suggest brief hiatuses.

Correlation: The Jacobs Chapel Bed belongs in the Kinderhookian Series and correlates with part of the Hannibal Shale of the Mississippi Valley. It also correlates within the lower part of the Coldwater Shale of northern Indiana and adjacent Michigan. The Conodonts are only slightly older than those of the Siphonodella isoticha-S. cooperi Assemblage Zone in the overlying Rockford Limestone, but a precise correlation with the Mississippi Valley standards is not feasible (Rexroad, 1969).