The lowermost of three members distinguished within the Nevada Group of the Sulphur Spring-Pinon Range area was named the McColley Canyon Member for exposures which conformably overly the Lone Mountain Dolomite along McColley Canyon in the northern Mineral Hill Quadrangle (Carlisle and others, 1957). Johnson (1962) raised the McColley Canyon to formational rank.

The McColley Canyon Formation is considered Lower to Lower-Middle Devonian (Pragian to Emsian) in age. It is a time-equivalent of the Beacon Peak Dolomite Member of the Nevada Group as defined by Nolan and others, 1956, and the Grays Canyon Limestone Member of the Nevada Formation in the Northern Fish Creek Range (Nolan and others, 1974). The McColley Canyon is partially equivalent to the Wenban Limestone in the Cortez Mountains. The Coils Creek Member of the McColley Canyon Formation is partially equivalent to the Oxyoke Canyon Sandstone and the Sadler Ranch Formation.

The McColley Canyon Formation is composed dominantly of medium to thick-bedded grey limestone with interbedded light brown-grey fossiliferous and organic-rich dolomite primarily in the lower 40 feet of the formation. Calcareous shale is common in the lower 50 feet of the unit in the Antelope Range (Hose and others, 1982). Well-rounded dolomitic quartz-rich sands up to 70 feet in thickness are reported in the Sulphur Spring-Pinon Range area. Light-yellowish grey, platy, argillaceous limestone, mainly wackestone and minor packestone and dolomitic pelletal packestone, are present in the upper 100 feet of the formation. Crinoidal packestones similar to those described at Lone Mountain are present in the upper 65 feet of the formation in the Antelope Range (Hose and others, 1982).

Facies changes occur within the McColley Canyon between western (offshore) localities of lime mudstone and wackestone as in the northern Simpson Park and Cortez Mountains, and eastern (onshore) localities where the McColley Canyon consists of various limestones, dolomitic limestones and dolomites as in the Sulphur Spring and Pinon Ranges (Matti and McKee, 1977). The McColley Canyon Formation gets younger to the south through the Roberts Mountains and Antelope Range (Murphy and Gronberg, 1970).

Murphy and Gronberg (1970) divided the McColley Canyon Formation into the Kobeh, Bartine, and Coils Creek Members in ascending order. All three members have their type section at Lone Mountain. They felt such a distinction could be mapped in at least the Sulphur Spring and Roberts Mountains, Lone Mountain, Table Mountain, and Simpson Park Ranges. The Kobeh Member is named after Kobeh Valley to the north and east of Lone Mountain where it conformably overlies the Lone Mountain Dolomite. Although the contact with the Lone Mountain is conformable, abundant evidence suggests that the upper surface of the Lone Mountain Dolomite had local relief before deposition of the McColley Canyon Formation (Murphy and Gronberg, 1970).

The Kobeh Member is a massive (4-16 inch thick beds) to faintly laminated, brown-grey to light grey, dolomite or dolomitic limestone. These carbonates are richly fossiliferous with abundant crinoids, corals, and brachiopods. Some beds are rich with quartz silt and/or sand, and are locally cherty (Murphy and Gronberg, 1970).

The Bartine Member is named after the Bartine Ranch, a few miles southwest of its type locality at Lone Mountain. The Bartine conformably overlies the Kobeh Member and is composed of thin to medium-bedded, medium-grey, fine-grained limestone and yellowish argillaceous limestone with abundant brachiopods.

The uppermost member is the Coils Creek, named for Coils Creek four miles to the west of Lone Mountain. The Coils Creek is a medium to thick-bedded, medium-grey, very fine-grained limestone which is only sparsely fossiliferous. The base of the Coils Creek is marked by a thin bed of quartz sandstone in the Roberts Mountains, and is entirely altered to dolomite at Lone Mountain (Murphy and Gronberg, 1970).

At Lone Mountain the Kobeh Member is about 185 feet of yellowish-brown to light-gray, thin-bedded, very fine-grained fossiliferous dolomite with scattered chert nodules (Gronberg, 1967). The overlying Bartine Member is about 455 feet of light gray to yellowish-orange, laminated to very thin-bedded, silty to argillaceous fossiliferous limestone (Gronberg, 1967).

At Table Mountain the Kobeh Member is about 135 feet of light blue-gray, very fine-grained, limey dolomite and about 35 feet of medium-gray crinoidal micritic limestone with thin beds of argillaceous limestone and scattered chert nodules (Gronberg, 1967). Overlying this is about 210 feet of the Bartine Member composed of medium gray to orange, laminated to thin-bedded, highly fossiliferous micritic limestone (Gronberg, 1967).

In the northern and southern Hot Creek Range, the Kobeh Member is about 105 to 480 feet of gray to yellowish, pinkish or brown, medium to thickly-bedded, pelletoidal, limey saccharoidal dolomite with chert lenses, thin beds of quartz-sand, and bioclastic beds with brachiopods, crinoids and horn corals. It is locally intensely bioturbated (Potter, 1976; McGovney, 1977). Overlying the Kobeh Member is about 90 to 490 feet of the Bartine Member (Potter, 1976; McGovney, 1977). It is composed of yellowish to light brown, thin to thick-bedded, highly fossiliferous, pelletoidal limestone and argillaceous mudstone with abundant brachiopods, gastropods, tabulate and horn corals, pelecypods, ostracodes, crinoids, bryozoa, trilobites, and nautaloids (Potter, 1976; McGovney, 1977).

In the southern Mahogony Hills, the Kobeh Member is light gray, very fine-grained and thin-bedded limestone and dolomitic limestone with dolomite increasing to the east (Schalla, 1978). The overlying Bartine Member is composed of about 140 feet of bioclastic, thin-bedded, aphanitic argillaceous and bioclastic limestone with brachiopods, trilobites, corals, bryozoa, and crinoids (Schalla, 1978).

In the northern Antelope Range, the Kobeh Member is about 225 feet of brown to gray, thin-bedded to medium-bedded, fine-grained dolomitic limestone with crinoids overlain by pelletoidal limestone with thin beds of yellow and pinkish argillaceous limestone and abundant brachiopods, corals, trilobites, gastropods, and echinoderm debris (Trojan, 1978). The overlying Bartine Member is composed of about 110 feet of very thin-bedded to medium-bedded yellowish pelletoidal limestone, and argillaceous mudstone (Trojan, 1978).

In the southern Cortez Mountains, the Kobeh Member is about 450 feet of light to medium-gray silty, laminated and sparsely bioturbated dolomitic limestone with 15 to 50 percent bioclastic debris and thin, locally cross-laminated quartz sandstone and siltstone beds which compose about 15 percent of the unit. The overlying Bartine Member is dark gray to black, very fine-grained, thin to medium-bedded, platy to blocky dolomitic, pelletoidal limestone with interlayered lavender shales and cross-laminated silty gray wackestones (Christiansen, 1980).

In the Sulphur Spring Range, the lower portion of the Bartine Member of the McColley Canyon Formation is composed of thin to medium-bedded, limey, yellow-gray dolomite with faint laminations and burrows in some beds (Kendall, 1975). Quartz arenite and quartzose dolomite are in thin lenses and interbeds up to a few feet thick. Brachiopods are abundant in some beds as are mud rip-ups and small channels (Kendall, 1975). This is overlain by light to dark gray, well-bedded, sparsely fossiliferous, locally burrowed, lime mudstone and moderately fossiliferous, thin-bedded to platy, lime packstones. Fossils include brachiopods and crinoids, gastropods, cephalopods, bryozoans, stromatoporoids, corals, ostracods, and trilobites (Kendall, 1975).

In the Diamond Mountains and Pinon Range, less than 20 feet of the Bartine Tongue of the McColley Canyon Formation has been described by Kendall (1975). It is composed of gray to yellowish-gray argillaceous thin to medium-bedded, laminated, slightly quartzose dolomitic mudstone. Very thin beds of intraformational conglomerate, ripup clasts, scours and burrows are present in the formation in these ranges (Kendall, 1975).

The McColley Canyon is about 330 to 650 feet thick in the Antelope Range (Trojan, 1978; Hose and others, 1982), 450 feet in the Cortez Mountains (Christiansen, 1980), 245 feet at Table Mountain (Gronberg, 1967), 635 feet at Lone Mountain (Gronberg, 1967), 340 feet in the southern Mahogany Hills (Schalla, 1978), 570 feet and 595 feet in the northern and southern Hot Creek Range respectively (Potter, 1976; McGoveney, 1977).

The McColley Canyon is recognized within the Mahogany Hills, Antelope and Hot Creek Ranges, Sulphur Spring, Simpson Park, Cortez, Diamond and Roberts Mountains, at Lone Mountain and Table Mountain.

The McColley Canyon contains a biofacies characteristic of warm, shallow marine low energy subtidal environment (Christiansen, 1980; Hose and others, 1982), including abundant tabulate and rugose corals, crinoids, bryozoans, echinoids and brachiopods. The accumulation of lime muds suggests quiet sheltered lagoons with scattered patch reefs (Hose and others, 1982). Matti and others (1974) have suggested a shallow-subtidal platform setting for these carbonates similar to the Lone Mountain Dolomite. Their model suggests deposition in a deep subtidal environment along a gently inclined ramp-like shelf. Christansen (1980) suggests that the Kobeh Member represents shallow subtidal and the Bartine Member represents deepening conditions and deep subtidal deposition. Kendall (1975) suggests that the Bartine Member represents intertidal to shallow subtidal deposition based upon the presence of laminations and cross-laminations, channels, abrupt lateral and vertical lithologic changes and burrowing. The Coils Creek Member has been ascribed to open marine conditions by Kendall and others (1983).