Platy limestone, dolomite and chert are characteristic of the auriferous Roberts Mountains Formation in Nye, Elko, Eureka, and Lander Counties and of the Masket Shale and Gatecliff Formation in northern Nye County. This unit lies with depositional contact over the Hanson Creek Formation of unit SOc of the Carbonate shelf sequence (unit OCc in southern Nevada), and is also structurally imbricated with Carbonate shelf sequence rocks (OCc) and other Slope and Basin assemblages rocks (units DCs, DOts, MDst) across its area of exposure. In the Carlin area, rocks assigned to the Popovich Formation and the informal Bootstrap Limestone (Berger and Theodore, 2005; Jory, 2002) are also included. In the Monitor Range, the Roberts Mountains, and the Sulphur Spring Range, unit DSt is mapped as stratigraphically overlain by unit DSc. To what extent this “overlying” dolomite is truly a stratigraphic unit as opposed to an alteration product of this unit (Nichols and Silberling, 1977a) is unclear. A stratigraphic contact with unit MDst in the Carlin area is possible based on recent mapping (Berger and Theodore, 2005; Theodore, Moring, and others, 2003).