The Beck Spring Dolomite (Pahrump Group, upper Precambrian) has an average thickness of 1,300 feet in the type area, Kingston Range, San Bernardino County, California, where it is divided into three unnamed members. The lower member, 500-700 feet thick, is composed of alternating laminae of finely crystalline and medium-crystalline dolomite mosaic. Allochem ghosts are scarce but include intraclasts and pellets. The laminae are primary features modified by replacement and recrystallization. The middle member, a replaced oolite calcarenite, is 300-400 feet thick, composed of finely to medium-crystalline dolomite mosaic with abundant ghosts of oolites, pisolites, and pellet-lump intraclasts. Selective replacement by quartz is fairly common, as well as re-dolomitization in so e places. The upper member, 400-500 feet thick, resembles the middle member, but is partly laminated, has been extensively replaced by chert, and is brecciated and recemented. Allochem ghosts are similar to those found in the middle member. Although contacts are gradational, the three members can be traced throughout the type area.

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