258 



University of California Publications in Geology [Vol. 8 



The principal results of the work in this field are (1) the recog- 

 nition of distinct faunal zones in the Chico; (2) the discovery of small 

 hut important areas of hoth Martinez and Tejon ; (3) the mapping 

 of areal relations; (4) the finding of well-marked unconformities 

 separating the various groups; and (5) the locating of both the 

 Turritella inezana zone and the Turritella ocoijana zone of the lower 

 Miocene. 



HISTORICAL 



The Cretaceous of the Santa Ana Mountains was known to Gabb 

 through collections made by Mr. Stephen Bowers. Cooper 1 described 

 Cucullaca bowersi and Crenella santana from this region. Goodyear 2 

 in a report upon coal of California gave descriptions of the coal mines 

 of this region and a few general notes upon the geology along Aliso 

 Creek. Dr. Stephen Bowers, 3 in an article upon the geology of Orange 

 County, recognized Miocene and Cretaceous in this area, listed about 

 thirty Chico species, and gave some interesting notes concerning the 

 coal mines of Santiago Canon. The occurrence of Chico Cretaceous 

 was briefly noted by F. M. Anderson. 4 Anderson placed the whole of 

 the Cretaceous as exposed in Silverado Canon in the Lower Chico. 

 The Triassic slates and limestones with their associated intrusives are 

 described by MendenhalP in a note to Bailey "Willis. 



LOCATION AND PHYSIOGRAPHIC FEATURES 



The Santa Ana Mountains are located about forty miles southeast 

 of Los Angeles and ten miles east of the town of Santa Ana. (See 

 plate 26.) The northern limit is marked by the canon of the Santa 

 Ana River. The area studied by the party during the past summer 

 was a strip about ten miles wide and fifteen miles long that extends 

 southeast from the Santa Ana River. The highest peak in the range 

 is Santiago Peak, elevation 5680 feet. (Plate 26.) The general height 

 of this southeast-northwest range is from three to four thousand feet. 



i Cooper, J. G., Catalogue of California fossils, Bull. Calif. State Mining 

 Bureau, no. 41, pp. 6-22, 1887. 



- Goodyear, W. A., Eighth Annual Report California State Mineralogist, 

 p. 338, 1888. 



s Bowers, Stephen, Tenth Annual Report California State Mineralogist, pp. 

 399-410, 1890. 



* Anderson, F. M., Cretaceous deposits of the Pacific Coast, Proc. Calif. 

 Acad. Sc., Third Series, Geology, vol. 2, no. 1, p. 26, 1902. 



5 Mendenhall, W. C, in Index to the stratigraphy of North America, U. S. 

 Geological Survey, Professional Paper, no. 71, p. 555, 1912. 



