146 SOUTHERN CALIFORNIA GEOLOGY 



tions made from hard field-work in that region. These 

 maps clearly show the meeting places of the north- 

 south, the northwest, and the east-west belts of 

 of structures. In fact, the district covered is a meet- 

 ing-place of all the great belts of structures mentioned. 



Three conspicuous, parallel, east-west lineaments are 

 here included in a belt about thirty-five miles wide. 

 They extend eastward from the vicinity of the San 

 Bernardino mountains and San Gorgonio pass to the 

 Colorado River between the towns of Needles and 

 Blythe. Their courses are marked by strong rectilin- 

 ear escarpments, the mountain and valley borders, 

 and other features characteristic of fault line topog- 

 graphy in California. They may be successively men- 

 tioned from north to south as the Pinto Mountain, 

 the Eagle Mountain and the Orocopia Mountain lines 

 respectively. Each of these apparently has a dis- 

 placement to the north, but the studies I have made 

 are as yet too insufficient to present details. 

 THE PINTO MOUNTAIN RIFT 



The course of the Anacapa Rift is resumed east 

 of the San Bernardino plateau by a great, rectilinear, 

 east-west lineament which I term the Pinto Mountain 

 Fault. This is first seen in the vicinity of the lo- 

 cality on the map of the San Bernardino quadrangle 

 designated as "The Pipes", and continues east, in 

 an almost straight line to the Colorado, past the south 

 side of the Dale Desert, the north side of the Morongo 

 (Little San Bernardino) and Pinto Mountains and 

 through the lately-mapped Dale Desert on into Ari- 

 zona about twenty-eight miles north of Blythe. This 

 is one of the three longest and most conspicuous fault 

 lineaments of California. There is some e\ddence 



