PHYSICAL GEOGRAPHY 95 



late Pleistocene and recent outwash materials from the 

 north which have been deposited by the many present 

 and former distributaries of the Los Angeles, San 

 Gabriel and Santa Ana Rivers, which still empty into 

 and widely spread their sediments over parts of it.^ 



THE DRAINAGE 



Should a map of Southern Cahfornia be made which 

 would show the paths which the drainage might follow, 

 it would constitute a bizarre pattern with many pe- 

 culiar deflections, cut-offs and captures quite different 

 in details from those which would be shown upon a 

 map of other regions, such as the Atlantic Coastal Plain 

 of the United States for instance, where the drainage 

 flows in parallel and orderly lines down a normal 

 coastward slope. The eccentricities of the drainage 

 pattern of the Southern California region are largely 

 due to adjustment to the structure by the stream 

 courses or to the cutting-off and dismemberment of 

 the former stream paths by later faulting and fold- 

 ings. In some instances the fault blocks have risen 

 directly across the antecedent paths of the streams, 

 in others the streams have swerved around the ends 

 of the rising blocks as they adjusted their courses to 

 them. Short, consequent streams also accompany and 

 conform to the steep slopes of the fault scarps and are 

 sometimes disjointed along horizontally sliding fault 

 lines. 



Sometimes great talus fans are formed where the 

 up-stream side of the country has been uplifted along 

 a fault line. The Coastal ends of the streams show 



'The reader who desires more detailed information concerning this inter- 

 esting valley plain, is referred to the excellent papers by W. C. Mendenhall 

 and W. A. English, published respectively as Water Supply Paper 139 and 

 Bulletin No. 768 of the United States Geological Survey. 



