The Pogonip Group, as adopted, represents Ordovician rocks between the top of the Cambrian Windfall Formation and the base of the Eureka Quartzite (Nolan and others, 1956). The Pogonip includes the Goodwin Limestone, Ninemile Formation, and Antelope Valley Limestone which are discussed separately within this report.

In western Elko County, subdivisions within the Pogonip agree with those of the Eureka area. In eastern Elko County, as well as within western Utah, the Pogonip has been divided where possible into the Garden City Formation, the Kanosh Shale, the Lehman Formation, the Swan Peak Quartzite, and the Crystal Peak Dolomite in ascending order (Coats, 1985). The Garden City Formation was named by Richardson (1913) for exposures at Garden City Canyon west of Bear Lake, Utah. The Kanosh Shale was named by Hintze (1951) for exposures near Kanosh, Utah. The Lehman Formation was named by Hintze (1951) for exposures near the Lehman Caves in the Snake Range of Eastern Nevada. The Swan Peak Quartzite was defined by Richardson (1913) for units exposed near Bear Lake, Utah. The Crystal Peak Dolomite was named by Webb (1956) for exposures north of Crystal Peak in the Confusion Range of western Utah.

Often the individual formations have not been broken out, and the Pogonip Group is retained as a mappable unit of medium to thick-bedded, fine to coarse-grained, chert-bearing and clastic limestones which weather a dark yellowish orange. These limestones commonly contain a few hundred feet of interbedded olive shale, and pinkish siltstone and limestone about 200 to 400 feet below the top of the formation. Some beds are fossiliferous, particularly with trilobites, while others contain abundant chert lenses and nodules and intraformational conglomerates (Tschanz and Pampeyan, 1970).

Much of the central portion of the Ruby Mountains is composed of fine-grained, light gray marbles with 80 to 95 percent calcite and minor diopside, potassium feldspar, biotite, plagioclase and quartz. This metamorphic unit has been correlated with the Pogonip Group by Howard (1971). In the Jiggs Quadrangle portion of the southern Ruby Mountains, the Pogonip has been divided into three units (Willden and Kistler, 1969). The lowest unit is gray, thin to medium-bedded, shaly limestone. The middle unit is medium to thick-bedded, cherty limestone with interspersed intraformational conglomerate. The upper unit is sandy dolomite, and calcareous, sandy siltstone and platy limestone. To the south in the Buck Mountain-Bald Mountain area, the unmetamorphosed Pogonip has been divided into individual formations (Rigby, 1960).

In the Toana and Goshute Ranges, the Pogonip overlies the Cambrian Notch Peak Formation and underlies the Eureka Quartzite in several intensely faulted plates (Pilger, 1972; Coats, 1985). The basal Garden City Formation is about 3,100 feet of highly argillaceous, nodular, gray, fine to medium-grained, crystalline limestone with brown and black cherty, thick-bedded limestone (Pilger, 1972; Coats, 1985). The overlying Kanosh Shale is about 275 feet of blue-brown dolomite, yellow shaly limestone, and gray cherty limestone, with thin cherty dolomite and a few thin beds of cross-bedded quartz-arenite near the base. Above the Kanosh is about 680 feet of the Lehman Formation which is a fine-grained, thin to medium-bedded, blue-gray, yellowish-orange weathering, argillaceous and fossiliferous limestone with gastropods and ostracods. The Lehman has a brecciated upper contact (Pilger, 1972). Above the Lehman is about 55 feet of the Swan Peak Quartzite and 50 feet of cherty gray dolomite of the Crystal Peak Dolomite which is in turn overlain by the Eureka Quartzite (Coats, 1985).

In the Pilot Range, all five members of the Pogonip were recognized by O'Neill (1968). The basal Garden City Formation is 2,515 feet thick. The basal unit is shaley, gray to brown, orange-yellow mottled limestone with lenses of intraformational conglomerate. The upper section is flaggy, light gray, yellowish-weathering limestone with chert nodules and stringers and interbedded gray dolomite (O'Neill, 1968). The overlying Kanosh Shale is about 215 feet of platy, dark red-brown and green mudstone and shale, and platy, fine-to medium-grained, argillaceous and silty limestone. The Lehman Formation is about 840 feet of flaggy, dark gray, orange to red mottled, medium-grained limestone. Overlying the Lehman is 46 feet of thin-bedded, very fine-grained, white to gray quartzite and lesser shaley calcarenite of the Swan Peak Quartzite. The Crystal Peak Dolomite forms the upper unit of the Pogonip Group as 320 feet of platy, dark gray to black, light gray weathering, argillaceous limestone overlain by the Eureka Quartzite (O'Neill, 1968).

In the Pequop Range, Thorman (1962, 1970) recognized 4 units within highly faulted blocks of the Pogonip Group. The lowest 585 feet were assigned to the Wah Wah-Juab Limestone which includes gray, thin-bedded and platy, fine-grained, argillaceous limestone, and gray sandy cross-bedded dolomite (Thorman, 1962). Overlying these carbonates is 580 feet of the Kanosh Shale which is dark gray to black, fissile shale with olive-gray interbeds in the lower portion, and local thin gray argillaceous limestone beds. Overlying the Kanosh is 580 feet of the Lehman Formation which is dark blue to gray, thin-bedded and platy limestone with thin 1 to 2 inch thick, gray, fine-grained dolomite stringers in the upper portion of the unit. The upper unit is the Crystal Peak Dolomite which is 180 feet of medium-grained, sandy, gray dolomite (Thorman, 1962; 1970).

In the Spruce Mountain Quadrangle (Hope, 1972), the Pogonip is thin-bedded to massive, gray limestone with shale partings, and a very fine-grained, granular, dark gray dolomite about 50 feet thick near the top of the formation. Only the Kanosh Shale was individually mappable as 200 feet of medium gray, very siliceous pyritic shale with thin gray silty limestone interbeds (Hope, 1972).

In the Windermere Hills, the Pogonip was divided by R. Hope (Coats, 1985) into about 800 feet of the Garden City Formation, 400 feet of Kanosh Shale, 200 feet of quartzite, and 1,075 feet of the Lehman Formation, which is overlain by the Ordovician Fish Haven Dolomite. In the Antelope Peak area (Petersen, 1968), about 250 feet of Pogonip is composed of massive, dolomitic, gray to brown, fine-grained and thin bedded limestone similar to about 480 feet of limestones assigned to the Pogonip in the northern Snake Mountains (Gardner, 1968). In the Snake Mountains, the Pogonip contains abundant slump structures, channel marks and cross-beds, intraformational conglomerate, and algal nodules (Gardner, 1968).

In the southern Deep Creek Range, the Pogonip consists of about 800 feet of massive, lenticular, reddish-weathering limestone and alternating thin-bedded, argillaceous limestone with brown chert laminae, overlain by about 1,000 feet of thin-bedded, argillaceous, brown-weathering limestone and about 400 feet of light gray, reddish-weathering limestone and interbedded dark brown and bluish-black, fissile shale (Nelson, 1959).

In the Marys River Basin Northeast and Mountain City Quadrangles, the Pogonip is composed of a few hundred feet of light gray to brown, massive to thin-bedded limestones which are locally silicified along granitic intrusives (Coats, 1985). In the Wild Horse Quadrangle, the Pogonip is a small fault sliver of gray intraformational limestone conglomerate (Coats, 1985).

The Pogonip Group is present in the Fish Creek, Antelope, Monitor, Toquima, Hot Creek Ranges, Roberts Mountains, and in the Lone Mountain and Eureka areas (Kleinhampl and Ziony, 1985; Roberts and others, 1967). In Lincoln County, it is found in the Quinn Canyon, Bristol and Wilson Creek Ranges (Tschanz and Pampeyan, 1970), and is exposed within all of the mountain ranges in White Pine County with the exception of the Butte Mountains where it is probably present at depth (Hose and Blake, 1976). In Elko County, the Pogonip is present in the Kingsley, Toana-Goshute, Pilot, Pequop, Ruby, and Pinon Ranges, Spruce Mountain, Snake Mountains, Windermere Hills (Coats, 1985), Jarbidge Wilderness, Mountain City and Wild Horse Quadrangles (Coats, 1985).

As a group, it is 1,600 to 1,800 feet thick in the Eureka area and as much as 3,545 feet in the southern portion of the Egan and Schell Creek Ranges (Kellogg, 1964). The Pogonip Group is also retained in the Grant, White Pine, and Horse Ranges where it is between 2,000 and 2,990 feet thick (Moores and others, 1968), and in the Quinn Canyon, Snake, northern Bristol and Wilson Creek Ranges where it is between 2,000 and 3,000 feet thick (Tschanz and Pampeyan, 1970). It is 4,500 feet thick in the Kingsley Range (Buckley, 1967), 4,290 feet in the Toana-Goshute Ranges (Coats, 1985), 2,200 feet in the southern Deep Creek Range (Nelson, 1959), 3935 feet in the Pilot Range (O'Neill, 1968), 2,500 feet in the Spruce Mountain Quadrangle (Hope, 1972), 1,855 feet in the Pequop Range (Thorman, 1970), 2,600 to 3,650 feet in the southern Ruby Range (Coats, 1985; Sharp, 1942), 350 feet are exposed in the Pinon Range (Smith and Ketner, 1975), 1,400 feet in the Jarbidge Wilderness portion of the Marys River Basin Northeast Quadrangle (Coats and others, 1977), about 478 feet are exposed in the northern Snake Mountains (Gardner, 1968), and about 300 feet are present in the Mountain City Quadrangle (Coats, 1985).

The Pogonip Group represents intertidal to subtidal shallow marine carbonates deposited in a variety of environments along the broad Ordovician shelf.

The three units commonly broken out as individual formations within the Pogonip Group in this evaluation area, the Goodwin Limestone, Ninemile Formation, and Antelope Valley Limestone, are discussed individually.