Structural Studies in the Whipple Mountains, Southeastern California

The rocks of the Whipple Mountains include a basement complex of pre-Cambrian age overlain by middle Tertiary volcanics and sedimentary. These are unconformably overlain by flat-lying Pleistocene and recent beds. The broad structural feature of the mountains is a faulted dome, elongated roughly east-west. The dome is out lined on the north and northeast flanks by an arcuate fault which dips away from the mountains. The northeast area of the mountains is broken into southwest-tilted blocks, bounded by northeast-dipping normal faults, roughly parallel to the southeast-trending portion of the arcuate fault. The block faulting is not of the orthodox basin range type, but is considered to be closely associated with the doming. There is no evidence of large compressional forces, and these mountains are believed to belong to the belt of transverse ranges of southern California. The major faults are presumed to have been active in post and pre-Miocene times. There is no evidence of recent fault activity and volcanics and sediments presumably of Quaternary age are not cut by the faults