The Slaven Chert is named for exposures along the hills west of Slaven Canyon in the eastern portion of T. 30 N., R. 46 E., six miles south of Mount Lewis in the Shoshone Range (Gilluly and Gates, 1965).

Fossils have been found in the Slaven Chert both in the Shoshone and Toiyabe Ranges. Ostracodes, tentaculitids, and brachiopods indicate a Middle to Late Devonian age (Gilluly and Gates, 1965; Stewart and McKee, 1977).

The Slaven is predominantly a sequence of highly contorted and broken, black, nodular, reddish weathering chert, with dark carbonaceous shale in partings separating chert layers which are commonly 4 to 10 inches in thickness. A few layers of brown-weathering brachiopod bearing limestone 2 to 20 feet in thickness are also locally present within the Slaven cherts. Without the shale and limestone partings and beds, it is difficult to distinguish between Slaven and Ordovician Valmy or Vinini cherts. Unlike the Vinini or Valmy Formations, however, Slaven cherts commonly form continuous sequences up to 300 feet in thickness with no interbedded siltstones or shales; the absence of quartzites also distinguishes Slaven Chert from either the Valmy or Vinini Formations (Gilluly and Masursky, 1965). Deposits of bedded barite are common within the Slaven.

Locally present are thin beds of brown-weathering calcareous sandstones up to a few tens of feet thick. These sands are composed of 50 to 60 percent well rounded (sand) to angular (silt) quartz, and 25 to 30 percent subrounded to angular chert, shale, limestone and greenstone clasts in a carbonate matrix (Gilluly and Gates, 1965). Dark carbonaceous shale is also locally present in the Slaven, in beds commonly 4 to 10 feet in thickness (Gilluly and Gates, 1965).

Well-sorted and rounded feldspathic siltstones resembling the Silurian Elder Sandstone make up a small portion of the Slaven. The siltstones are about 75 percent quartz and 20 percent potassium feldspar, with minor amounts of muscovite, iron oxides, and organic matter (Gilluly and Gates, 1965).

Limestones, although minor, are more abundant in the Slaven exposed in the Cortez Mountains than at the type section in the Shoshone Range (Gilluly and Masursky, 1965). These limestones are thin to thick-bedded, gray, bioclastic and sandy and are similar to those found in the Devonian Wenban Formation. The limestones in the Cortez Mountains contain brachiopods similar to those in limestone interbeds in the Shoshone Range.

Both the upper and lower contacts of the Slaven Chert are structural contacts (Gilluly and Masursky, 1965). Poor exposure, complex faulting, and intricate folding make estimates of thickness nothing more than guesses which have been estimated at 200 to as much as 4,000 feet in the Shoshone Range (Gilluly and Gates, 1965).

The Slaven Chert is exposed in the Shoshone Range and Cortez Mountains.

The details of original depositional setting are poorly understood for the allochthonous Slaven Chert which now lies within the upper plate of the Roberts Mountains thrust. This sequence of chert, siltstone and sandstone and limestone represents marine deposition, probably in a trench or subduction zone setting. Water depths are very difficult to determine for the Slaven with the exception of limestones. The limestones within the Slaven contain corals, bryozoa and brachiopods that suggest initial deposition under shallow marine conditions. It is certainly possible that these limestones were redeposited under deep marine conditions as turbidites. The cherts, siltstones, and sandstones may represent relatively deep marine deposition within the subduction complex.