From abstract: The region described in this report includes a foothill belt of the San Emigdio and Tehachapi Mountains along the southern border of San Joaquin Valley. The belt displays portions of the rugged granitic cores of the mountains and also rocks of Eocene, Oligocene, Miocene, Pliocene, and Pleistocene age. Although there is thus a complete representation of the geologic series from the Eocene to the Pleistocene, some portions of the different series are wanting because of major faults and overlaps. The thickness of the Tertiary rocks (Eocene to Pliocene) varies considerably but has a maximum of about 29,000 feet. Miocene and Pliocene rocks cover most of the area investigated.

From introduction: The investigations on which the greater part of this report is based were carried on by E. T. Hancock, the senior author, during the summer of 1911. They were undertaken by the United States Geological Survey under a comprehensive plan for collecting information about the undeveloped fuel resources of the Western States, both as a step toward the conservation of the coal resources of the United States and as a means of supplying the demand for information concerning the many valuable coal fields of the Western States.