Basinal Permian sedimentary rocks of southern Nevada accumulated west and northwest of the Las Vegas hinge-line in a depocenter east of the Southern Nevada Highland; a substantially thinner contemporaneous shelf or platform facies formed to the east and southeast. Transgressive-regressive sedimentation in Wolfcampian through Early Guadalupian time accounted for variations in facies in the basin, shelf and bank margins, banks, lagoons, and deltas. Organic reefs, back reefs, and fore reefs dominated the sedimentary pattern at some times and places.

Sediments of Wolfcampian and Early to Medial Leonardian age consist of 4,500 feet of fusulinal, coralline, algal, bryalgal, and micritic limestones, and thick bioclastic limestones. This sequence comprises the Spring Mountains Formation, a basinal succession that accumulated in the miogeosyncline.

During Medial to Late Leonardian time, influx of terrigenous material from adjacent uplands accounted for substantial amounts of silty and sandy detritals in the carbonates which were forming on the shelf, hinge-line, and proximal parts of the basin; areally extensive red-colored sandy limestones, dolomitic siltstones and sandstones, and sandy dolomites thus formed in lagoonal, intertidal, bank, bank margin, and epineritic zones. This sequence is 3,000 feet thick, and comprises an unnamed formation; it interfingers across the hinge-line area and onto the platform with deltaic, neritic, and eolian sandstones and red beds of the Queantoweap, Hermit, and Coconino Formations.

Late Leonardian and Early to Medial Guadalupian time saw the filling of the basin; red -bed sedimentation of the Toroweap siltstone-shale-gypsum sequence was followed by carbonate sedimentation of the upper Toroweap and Kaibab. This succession is normally less than 1,000 feet thick in the Spring Mountains, but thickens to the east. The Kaibab Formation is in large measure reefal, and resembles the reef-tract of the West Texas Permian, but differs in that it is stretched out, has greater length, and is substantially thinner. The sponge Actinocoelia sp., cf. A. maeandrina Finks is characteristic.

The Triassic Moenkopi Formation rests unconformably upon the Kaibab; east of Las Vegas the formation is dominated by red beds, but in the Blue Diamond Mountain area it contains more than 700 feet of micritic, oolitic, pelletal, and algal limestones (= Virgin Limestone Member) near its base.

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