Name Carrier Mills Shale Member of Spoon Formation proposed for distinctive hard, black, fissile shale, 2.5 to 5 ft thick occurring 5 to 15 ft above the Stonefort Limestone Member and at or near the base of the sub-Davis sandstone in the Carrier Mills quad, Saline Co., IL. Shale is very thinly laminated and splits readily into sheets. Pyrite is common. Unit crops out in all three quads of report area and in adjacent quads to the north. Widely traceable in the subsurface. Thickness at type locality is 2.5 to 4.0 ft. Separated from the sub-Davis sandstone above by 0 to 10 ft of medium to dark gray, smooth to silty, well-laminated shale. Separated from the Stonefort Limestone Member below by medium gray to olive gray soft claystone.

Source: GNU records (USGS DDS-6; Reston GNULEX).