Geologic map of Alberhill Coal and Clay Company clay deposits, Riverside County, California: Supplement 6 from "I. Geology of the Southwest quarter of the Elsinore Quadrangle. II. Geochemical properties of the waters of the Elsinore Quadrangle [= Geology of the Lake Elsinore Quadrangle, California. Mineral deposits of Lake Elsinore Quadrangle, California]" (Thesis)

The Lake Elsinore quadrangle covers about 250 square miles and includes parts of the southwest margin of the Perris Block, the Elsinore trough, the southeastern end of the Santa Ana Mountains, and the Elsinore Mountains. The oldest rocks consist of an assemblage of metamorphics of igneous effusive and sedimentary origin, probably, for the most part, of Triassic age. They are intruded by diorite and various hypabyssal rocks, then in turn by granitic rocks, which occupy over 40 percent of the area. Following this last igneous activity of probable Lower Cretaceous age, an extended period of sedimentation started with the deposition of the marine Upper Cretaceous Chico formation and continued during the Paloecene under alternating marine and continental conditions on the margins of the blocks. A marine regression towards the north, during the Neocene, accounts for the younger Tertiary strata in the region under consideration. Outpouring of basalts to the southeast indicates that igneous activity was resumed toward the close of the Tertiary. The fault zone, which characterizes the Elsinor trough, marks one of the major tectonic lines of southem California. It separates the upthrown and tilted block of the Santa Ana Mountains to the south from the Perris Block to the north. Most of the faults are normal in type and nearly parallel to the general trend of the trough, or intersect each other at an acute angle. Vertical displacements generally exceed the horizontal ones and several periods of activity are recognized. Tilting of Tertiary and older Quaternary sediments in the trough have produced broad synclinal structures which have been modified by subsequent faulting. Five old surfaces of erosion are exposed on the highlands. The mineral resources of the region are mainly high-grade clay deposits and mineral waters.Cataloger's note: Engel, Rene. I. Geology of the Southwest quarter of the Elsinore Quadrangle (1933). No copies [of this thesis] have ever been presented to C.I.T. The thesis has been published under the title: Geology of the Lake Elsinore Quadrangle, California (in Bulletin no. 146 of the California Division of Mines). …Bulletin 146, a book containing two papers: Geology and Mineral Deposits of the Lake Elsinore Quadrangle, California, prepared by Rene Engel, and Mineral Deposits of Lake Elsinore Quadrangle, California by• Rene Engel, Thomas E. Gay, Jr., and B. L. Rogers. The principal author, Dr. Engel, first began studying the geology of this area in detail in the 1920's; he has been working with it intermittently since then. The second paper, which is primarily concerned with the economic mineral deposits of the area, was compiled by two staff members of the Division of Mines, Messrs. Gay and Rogers, working under the supervision of Dr. Engel…. 7 plates included in the Bulletin have also been scanned and included as part of this record