The Van Duzer Limestone is named for exposures along Van Duzer Creek in T. 45 N., R. 53 E., along the eastern flank of the Bull Run Mountains in northern Elko County (Decker, 1962).

The Van Duzer was originally considered Devonian in age by Decker (1962). Coats (1985) suggests that overlapping faunal assemblages suggest a Middle Pennsylvanian (Desmoinesian) age for the Van Duzer while admitting the formation may include Lower Permian age rocks. The Van Duzer is overlain by Ordovician western assemblage rocks along the Trail Creek thrust (Decker, 1962).

The Van Duzer Limestone consists of massive to thinly bedded, blue-gray limestone with thin argillaceous or shaley limestone laminations. Alternation of blue-gray and white beds give the formation a laminated appearance (Decker, 1962). Locally the Van Duzer has been recrystallized to marble along several small intrusive bodies.

Beneath the Van Duzer in the Bull Run Mountains are the Chellis Limestone and Storff Formation, both of which were tentatively assigned a Silurian age by Decker (1962). No fossils have been found within the formations but their position beneath the Pennsylvanian Van Duzer suggests that they are probably in part Pennsylvanian and perhaps Mississippian in age. The Storff was named for exposures along Storff Creek in T. 44 N., R. 52 E. and consists of about 3,900 feet of black to brown, thin-bedded phyllite and slate interbedded with argillaceous limestone (Decker, 1962). Structurally and perhaps stratigraphically beneath the Storff is the Chellis Formation named for the Chellis Mine in T. 44 N., R. 51 E., and consists of about 1900 feet of blue-gray, fine-grained, laminated or massive limestone with interbedded argillaceous and dolomitic beds near the base, and occasional 1 inch thick dark-gray chert beds (Decker, 1962). The Chellis and Storff only crop out in the Bull Run Mountains and were included locally with the Hammond Canyon and Poorman Peak in mapping.

In the northern Rowland Quadrangle, Bushnell (1967) mapped a contact metamorphosed Paleozoic limestone and argillite sequence which Coats (1985) considered part of the Van Duzer Limestone and mapped the two together. That practice is followed here as well. The basal part of this sequence is thick-bedded to laminated, dark gray to grayish black, argillite with strongly developed cleavage and tight folding, interbedded with crystalline, micaceous light to dark gray, laminated limestone (Bushnell, 1967). The upper member is composed of thinly laminated, medium to dark gray weathering, aphanitic limestone which is locally metamorphosed to marble along intrusive contacts (Bushnell, 1967). In some exposures beds of light gray and black chert up to several inches in thickness alternate with the limestone layers (Bushnell, 1967).

In the Owyhee Quadrangle the Van Duzer is thin-bedded to medium-bedded dark gray calcarenite which grades into quartzite and contains minor flows of meta-andesite which are now chloritic schists (Coats, 1971).

The Van Duzer is about 7,200 feet thick in the Bull Run Quadrangle (Decker, 1962), and about 7,000 feet thick in the Owyhee Quadrangle (Coats, 1971).

The Van Duzer Limestone is present in the Bull Run, Owyhee, and Rowland Quadrangles in northern Elko County.

The Van Duzer Limestone probably represents deposition under relatively quiet and moderately deep marine conditions. The presence of bryozoans, brachiopods, conodonts and shelly fauna constrain water depths. The details of the depositional setting are not understood.