PHYSICAL GEOGRAPHY 93 



Jacinto fault which borders the west side is probably 

 of Pleistocene age. 



The northern end of the Peninsula Plateau is char- 

 acterized by the many northwest-southeast-extending 

 master faults which cross it diagonally. The more 

 conspicuous of these faults in turn block out many 

 ranges and valleys of considerable magnitude. Among 

 the mountains are the San Jacinto, Badlands, Lake- 

 wood, Santa Ana, Dominguez, and San Joaquin Ranges. 

 The valleys include the Beaumont Plain, and the San 

 Jacinto, Perris and Elsinore Valleys and the Downey 

 Valley Plain. 



THE DOMINGUEZ RANGE 



The Dominguez Range is Southern California's new- 

 est, most valuable, and most interesting mountain 

 feature. It consists of a line of low, domical hills which 

 arise on a more or less continuous fold and which ex- 

 tend northwestward and southeastward like a beaded 

 necklace from Balboa to the Santa Monica Range. Bor- 

 dering the nearby Pacific Ocean for much of its course 

 it constitutes a topographic divide between it and 

 the Downey Plain. The range includes such hills as 

 Bolsa Chica, Alamitos, Signal, Dominguez, Athens, 

 Inglewood and some others north of Culver City. The 

 range is so new that its surface contours still largely 

 conform to the structure of the underlying folds. We 

 have data for very definitely placing the age of this 

 range as that of the latter half of the Pleistocene 

 Epoch.i The fold is attended largely on its seaward 

 side by the Inglewood fault, herein previously de- 



'The writer has in hand a large unfinished manuscript on the Pleistocene 

 and Recent Geology of the Los Angeles City Region which deals with the 

 subject and the age of the La Brea and Ballona fossil remains. 



