The Carlin Sequence as amended from Roberts and Thomasson (1964) by Coats (1985) includes the Buckskin Mountain, Beacon Flat, and Carlin Canyon Formations in a conformable and ascending sequence (Fails, 1960). The Strathearn Formation has locally been included with the unit during mapping in Elko County. The Moleen, Tomera and Tonka Formations, originally included by Roberts and Thomasson (1964), have commonly been mapped separately over most of the area, but may also be locally included, particularly in the western portion of Elko County. The Carbon Ridge and Garden Valley Formation have also been locally mapped in the Carlin Sequence by other workers but are individually mapped and described in this report.

The Carlin Sequence is here considered the Lower to Middle Permian (Wolfcampian to Guadalupian) marine sedimentary section comprised by the Buckskin Mountain, Beacon Flat, and Carlin Canyon Formations which are described below from youngest to oldest, where they have been individually differentiated.

In several cases, workers have not differentiated individual formations within the sequence, and simply map units as part of the Carlin Sequence. In some areas the units cannot be easily separated as in the Carlin-Pinon Range (Smith and Ketner, 1975) where abrupt lithic changes between various units make formation designation impossible, and the entire unit is mapped as a single Permian sequence. This sequence includes thin-bedded and platy yellow, tan and reddish siltstone; medium to coarse-grained, brown calcareous sandstone with pebbles and fragments of gray, green, tan and white chert; chert-pebble conglomerate beds 2 to 12 inches thick with angular to well rounded gray, tan and white chert pebbles up to 1.5 inches in diameter; and thin-bedded and locally laminated, gray dolomite and limestone which are locally silty and contain gastropods, bryozoans, and light brown chert layers 1 to 3 inches thick (Smith and Ketner, 1975).

About 900 feet of strata mapped as the Phosphoria Formation by Bezzerides (1967) in the O'Neil Pass area of the Snake Mountains were included in the Carlin Sequence in later mapping by Coats (1985). These rocks include poorly exposed, dark gray-brown, locally carbonaceous and calcareous siltstone, interbedded with micritic gray limestone up to 25 feet thick, bedded and nodular black chert, and black phosphorite beds up to 2 feet thick which are concentrated in the upper portion of the unit (Bezzerides, 1967). These rocks overlie the Oquirrh Formation and underlie the Triassic Dinwoody Formation.

The Carlin Sequence as adopted here, is mapped within the Carlin-Pinon and Adobe Ranges, Snake and Leach Mountains, Windermere Hills, and HD Range.