In the study area, the Wash Creek Slate of the Kahatchee Mountain Group is subdivided into four members: an unnamed ferruginous sandstone member (250 ft above the base of the Wash Creek), the Hillsdale Sandstone Member (new), the Kalona Quartzite Member, and the Mount Zion Church Member (new). The Mount Zion Church consists of black carbonaceous and occasionally graphitic dolomitic shale or slate. Slates appear massive, but are laminated, and locally interstratified with thin-bedded, dark-gray micaceous siltstone. Underlies Shady Dolomite in the study area and Jumbo Dolomite in the type area. Contact with the Shady has not been recognized, but contact with the Jumbo is interlayered. In the study area, unit occurs along the front slope of Columbiana Mountain where it is 226 ft thick. Age of the Wash Creek and its members is Early Cambrian(?), constrained by the ARCHAEOCYATHUS recently recovered from the Jumbo Dolomite by McKinney and others (1988).

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