ABSTRACT
In the region of Recruit Pass the Temblor Range consists of Miocene strata overlain by pre-Cretaceous crystalline rocks and Oligocene and upper Miocene sediments of the Recruit Pass thrust sheet. This thrust cover was folded with the underlying strata, though in somewhat lesser degree.
The Recruit Pass fault on the southwest flank of the range dips southwestward toward, and in places is seen to be cut by, a northwest-trending vertical fault. This is believed to be the northeasternmost element of the San Andreas Rift zone, a strip 2 miles wide covered by faulted Pliocene, bounded on the southwest by the line of recent activity that is generally called “the Rift.” The crystalline rocks are not native to Temblor Range but were thrust over it from a source either within, or to the southwest of, the Rift zone.
The major movement on Recruit Pass fault was certainly pre-Quaternary and perhaps as early as latest Miocene. It is suggested that movement began during Santa Margarita (upper Miocene) time, and that the materials of the fanglomerate lenses in Santa Margarita shale found on the northeast flank of the range came from the crystalline rocks which were thrust into the area tributary to the basin of shale deposition.
