Description
The Shadow Mountains are a range of small hills immediately south of Kingston Peak in eastern San Bernardino County, California. They contain allochthonous plates of Precambrian granites, gneisses, schists, mafic dikes, rocks of the Pahrump Group, and Paleozoic metasediments, all of which overlie authochthonous Tertiary lake beds. This allochthonous sheet, which now consists of what are probably klippen, forms the upper plate of what is interpreted to be a gravity slide at least ten miles long by six miles wide. It slid onto the Tertiary lake beds, causing very little deformation in these sediments. The slide took place less than 13.7 ± 0.8 million years ago according to a potassium-argon date on an andesite flow within the lake beds. Farther to the east is Shadow Mountain which rises above the Tertiary sediments, and contains the Winters Pass Thrust plate. Gravity slide blocks flank it on the west and north.
