The Laketown Dolomite was named for exposures in Laketown Canyon in the Bear River Range, within the Randolph Quadrangle of northern Utah (Richardson, 1913).

Corals, brachiopods, and algae show that the Laketown Dolomite is Middle to Late Silurian (Llandoverian to Pridolian) in age. Several geologists have mapped the Laketown and underlying Fish Haven Dolomites as a single unit because their gradational lithologic nature makes placement of contacts interpretational. The contact with the overlying Sevy Dolomite is easily mapped as a change to darker, coarser grained more massive dolomites (Hose and Blake, 1976). The Laketown Dolomite is present in and to the east of the Pancake Range in Nye County, and is designated as the correlative Lone Mountain Dolomite in and west of the Hot Creek Range.

In general, the Laketown Dolomite is a fine to medium-grained, massive, dark-gray dolomite which contains sparse nodules of dark chert, weathers to an olive gray, and includes prominent layers of light-olive-gray saccharoidal dolomite which weather to a yellowish-gray in the upper portion of the unit (Kleinhampl and Ziony, 1985; Tschanz and Pampeyan, 1970; Hose and Blake, 1976). The saccharoidal dolomites commonly contain dascycladacean algae about half an inch in diameter which resemble crinoid stems, and pentameroid brachiopods. A layer of quartzitic chert 3 to 10 feet thick is commonly present near or below the middle of the formation (Hose and Blake, 1976), and scattered dark-gray chert nodules and beds are common in most sections in the upper and lower portions of the unit (Kleinhampl and Ziony, 1985). Sedimentary breccias, locally of solution origin, are present in many sections in Nye County (Kleinhampl and Ziony, 1985). Brachiopods, solitary and colonial corals, and pelmatazoan debris are locally abundant within the Laketown. Bioherms of Favositid corals were reported by Kellogg (1963) in the Egan Range.

In the Pancake Range, the Laketown is a gray to light tan, coarse-grained, unfossiliferous dolomite. Dreessen (1969) noticed that the lower 300 feet are medium-gray dolomite with occasional dark-brown bands of dolomite, the middle 75 feet are a light-gray coarse-grained, massive cherty dolomite, with the upper 250 feet composed of medium to coarse-grained, light to dark-gray dolomite interbedded with very fine-grained dolomite that is more abundant near the top of the section.

In the Grant Range, the Laketown consists of three members (Moores and others, 1968; Hyde and Huttrer, 1970). The lower portion of the formation is a gray, coarse-grained dolomite about 950 feet in thickness, overlain in turn by fine-grained, dark-gray to brown, reddish-weathering dolomite about 200 feet thick and an upper light-gray, coarse-grained, dolomite also about 200 feet in thickness. Brachiopod and coral debris, and dark chert nodules and thin lenses, are present throughout the dolomite which gradationally overlies and underlies the Fish Haven and Sevy Dolomites respectively (Moores and others, 1968). In the White Pine Range, the Laketown is composed of medium to coarse-grained, light gray, thick-bedded to massive dolomite with a few beds of dark gray dolomite (Gaal, 1958).

In the Egan Range, Kellogg (1963) divided the Laketown into a lower brownish fine-grained siliceous dolomite, and an upper yellowish gray medium-grained dolomite. Numerous corals, as well as pentamerid brachiopods and crinoids are present in the Laketown here. Chert nodules are present throughout the dolomite. A 2 foot layer of massive chert in the lower dark dolomites in the southern Egan Range may correlate with a chert that marks the contact between the Hanson Creek Formation and basal Roberts Mountains Formation near Eureka (Nolan and others, 1956).

In the Snake Range, the Laketown is a light to medium-gray, fine to medium-grained, laminated to mottled dolomite which weathers a yellowish gray in the upper portion and a brownish gray below (Whitebread, 1969). Very fine-grained dolomites are present in an interval about 50 feet in thickness in the upper portion of the formation. Bedding is commonly from 2 to 18 inches in thickness, and occasionally accentuates a color banded appearance where light and dark dolomites alternate. Crinoid, tetracoral, and brachiopod debris are locally abundant. Several beds and lenses of intraformational conglomerate and breccia 10 to 30 feet in thickness are present in the middle portion of the dolomite, and light gray chert lenses and nodules, locally replacing coralline debris, are abundant throughout in beds 2 to 12 inches in thickness (Whitebread, 1969). Several zones tens of feet in thickness are quite porous and vugular.

In the Schell Creek Range, Dechert (1967) mapped the Fish Haven and Laketown as one sequence with apparent fault duplication. The lower 270 feet are assigned here to the Fish Haven, with the remaining 1780 feet representing a fault repeated section of the overlying Laketown Dolomite. The Laketown here is dark to light gray and brown gray, medium-grained dolomite in alternating units from a few feet to a few hundred feet thick (Dechert, 1967). Laminations are found locally as are contorted slump structures. Light gray and black chert nodules and beds of chert up to 40 feet thick are locally present and concentrated in the upper portion of the unit (Dechert, 1967). Young (1960) described the Laketown in the northern Schell Creek Range as about 1,000 feet of medium to dark and light gray, thick-bedded dolomite. The upper beds are massive and locally appear reefoidal or biohermal, and have been altered by both silicification and dolomitization. A 20 to 30 foot thick zone of algal limestone is exposed about 200 feet above the base of the Laketown (Young, 1960).

In the Kern Mountains and southern Deep Creek Range, four members are recognized within the Laketown (Nelson, 1959, 1966). The basal member is thick, black-weathering dolomite and alternating gray dolomite, with a brachiopod-rich bed near the base. This is overlain by a medium-gray, coarsely-crystalline dolomite, a member of gray nodular-chert bearing dolomite, and a member of light to medium-gray, saccharoidal dolomite with an upper brecciated zone near the top (Nelson, 1966). In the western Red Hills west of the Kern Mountains, the Laketown is structurally dismembered and mainly composed of strongly slickensided and brecciated dark brown-gray, cherty, brachiopod and coral-rich dolomite (Bartel, 1968).

In Lincoln County, Tschanz and Pampeyan (1970) describe the Laketown in the southern Schell Creek and Golden Gate Ranges and Limestone Hills as a light and dark-gray, medium-to coarsely crystalline dolomite. The base of the Laketown in the southwestern portion of the county is a grayish-yellow thin-bedded silty dolomite.

In the southern Pilot Range, the Laketown is composed of a lower section of 250 feet of thin to thick-bedded, gray to black dolomite and calcareous dolomite, overlain by a middle section of 140 feet of gray, calcareous dolomite. The upper 150 feet of the Laketown is light gray to white, coarse-grained, argillaceous dolomite (O'Neill, 1968). Bedding in the Laketown is commonly from several feet to more than 20 feet in thickness and thin chert stringers and nodules are locally abundant.

In the Goshute and Toana Ranges, the Laketown Dolomite overlies the Fish Haven as light gray, massive to sugary dolomite with thin argillaceous partings (Coats, 1985). In the Pequop Range the Laketown is composed of three informal members (Thorman, 1970). The lowest 390 feet are medium-bedded, gray dolomite with thin-bedded shaly dolomite near the base. The middle member is thick-bedded, dark gray dolomite. The upper 580 feet are a medium-bedded, light gray dolomite (Thorman, 1962).

Thicknesses in the Laketown Dolomite vary from 625 feet in the Pancake Range (Dreessen, 1969) and about 1,550 feet in the southern Pancake Range (Scott, 1969), 1,013 feet in the Egan Range (Kellogg, 1963) and 960 feet near Lund (Playford, 1961), about 1,350 feet in the Grant Range (Moores and others, 1968), 700 feet in the western White Pine Range (Gaal, 1958), 1,780 feet in a duplicated section in the Schell Creek Range (Dechert, 1967) and about 1,000 feet in the northern Schell Creek Range (Young, 1960) and 600 feet in the central Schell Creek Range (Drewes, 1967), 500 feet in the southern Snake Range (Drewes, 1958) where a combined Laketown-Fish Haven Dolomite section is 1,500 feet thick (Whitebread, 1969), 1,050 feet in the Kern Mountains (Nelson, 1966), 1,100 feet in the Silver Island Range (Blue, 1960), 500 to 600 feet in the southern Pilot Range (O'Neill, 1960), 750 feet in the Goshute Range (Coats, 1985), 1,500 feet thick in the Toana Range (Coats, 1985), and 1,100 feet in the Pequop Mountains (Thorman, 1970).

Variations in thickness are probably a combination of placement of the contacts in varying places by various geologists and structural complexities. An unconformity may locally be present at the top of the Laketown (Osmond, 1954) as described in the White Pine Mountains by Lumsden (1964), and the Egan Range by Kellogg (1963). In some localities the top of the Laketown is a fault zone as reported in the Red Hills (Bartel, 1968) and Kern Mountains (Nelson, 1966).

The Laketown Dolomite is exposed in the Pancake, Grant, White Pine, Quinn Canyon, Egan, Horse, Schell Creek, Snake, Ely Springs, southern Schell Creek, and Golden Gate Ranges, Limestone Hills, Silver Island, Pilot, Goshute, and Toana Ranges, Pequop and Kern Mountains, and Wood and Red Hills.

The presence of pentamerid brachiopods and Verticillopora algae (Limestone Hills), and abundant chain and honeycomb corals of the Halysites and Favosites varieties attest to the shallow open marine, subtidal to peritidal shelf nature of the Laketown. Lithologic changes within the unit suggest the Laketown represents a large-scale upward shallowing sequence (Johnson and Murphy, 1984).

Many sections of the Laketown are both vugular and porous suggesting the formation has potential as a reservoir. Secondary dolomitization of the Laketown may provide possible stratigraphic plays, particularly along the shelf margin.