The Tomera Formation was named for the Tomera Ranch in Sec. 25, T. 33 N., R. 53 E., at the northern end of the Carlin-Pinon Range (Dott, 1955). The type section is designated in Sec. 34 and 35, T. 33 N., R. 54 E., and Sec. 19, T. 33 N., R. 55 E. (Dott, 1955).

The Tomera Formation is Middle Pennsylvanian (Atokan through Desmoinesian) in age. The Tomera is equivalent to the upper part of the Ely Limestone (Dott, 1955). The Tomera gradationally overlies the Moleen Formation and is unconformably overlain by the Pennsylvanian and Permian Strathearn Formation.

The Tomera Formation consists of interbedded and interfingering fragmental and fossiliferous light to dark gray limestone with brachiopod coquinas and very rare nodular chert beds, gray-brown chert-pebble conglomerate with gray and green chert and minor quartzite in a sandstone or siltstone matrix, and very thin black shales (Dott, 1955; Smith and Ketner, 1975). In the Elko area, about 83 percent of the formation is limestone and 17 percent is composed of clastics (Dott, 1955).

Rigby (1960) assigned about 285 feet of strata in the Buck Mountain-Bald Mountain area to the lower portion of the Tomera Formation. It is composed of quartzite-chert-pebble conglomerate which grades both laterally and vertically into silty and pure limestone, and thin sandstone.

Kleinhampl and Ziony (1985) described about 3,500 feet of the Ely Formation in the Pancake Range near Duckwater. The upper 1,500 feet are thin-bedded to laminated, light-gray limestone with intercalated brownish-weathering layers and lenses of quartz sand, sandy limestone, and chert-pebble conglomerate. Mount (1972) broke the Ely interval into the Tomera and Moleen Formations with the upper Tomera equivalent to the upper member of the Ely described by Kleinhampl and Ziony (1985). The Tomera is composed of medium to thick-bedded, silty and sandy, bioclastic limestone with interbedded chert- and quartzite-pebble conglomerate and calcareous sandstone. The conglomerate forms prominent ridges in outcrop, with subrounded pebbles of green, red, and brown chert and gray quartzite in a quartz sand matrix cemented by calcite (Mount, 1972).

The Tomera is 1,700 to 2,000 feet thick in the Carlin-Pinon Range area (Dott, 1955; Smith and Ketner, 1975), 606 feet in the in the Diamond Mountains (Dott, 1955), 1,335 feet in the central Pancake Range (Mount, 1972), and about 285 are exposed in the Buck Mountain - Bald Mountain area (Rigby, 1960).

The Tomera is present in the Elko area, Diamond Mountains, Carlin-Pinon and central Pancake Ranges, and the Buck Mountain - Bald Mountain area, with perhaps 30 percent of the original areal distribution of the unit removed by erosion (Dott, 1955).

The Tomera is time equivalent to the upper portion of the Ely Limestone. It represents submarine fan-delta deposition in a local basin along the western margin of the Antler foreland. The total percentage of conglomerate increases to the west and northwest within the Tomera (Smith and Ketner, 1975).