Wash Creek Slate of Kahatchee Mountain Group is subdivided in this report into an unnamed ferruginous sandstone member (250 ft above the base of the formation), the Hillsdale Sandstone Member (new), the Kalona Quartzite Member, and the Mount Zion Church Member (new). The Hillsdale is the most areally extensive of the members. In the northern part of the region it occurs at the base of the Columbiana thrust sheet and underlies the Kalona Quartzite Member. In the southern region it occurs between the ferruginous sandstone member and the Kalona in the Kahatchee Mountain thrust sheet. Structural thickness is 4,374 ft in the southern area, where it is folded and faulted. Member can be divided into two parts. The lower part is dominated by black horizontally-laminated clay slate or shale interlayered with thin-bedded medium-gray laminated siltstone and fine-grained sandstone. Upper part consists of interlayered dark-gray horizontally laminated micaceous siltstone and medium- to dark-gray thin-bedded pyritic feldspathic sandstone. Black carbonaceous to graphitic clay slate is also present. Age of the Wash Creek and its members is Early Cambrian(?).

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