218 SOUTHERN CALIFORNIA GEOLOG^■ 



TESTIMONY OF THE STRATA 



There are many instances of age sequence in the 

 fault groups which have been determined by strati- 

 graphic and paleontologic details. 



Merriam and others have shown that the earlier 

 filled-in sediments between the Basin Ranges contain 

 Miocene vertebrate fossils; whence he deduced the 

 fact that the faults which made these valleys were 

 of Miocene or earlier periods. 



The Colorado Desert end of the graat Gulf of Cali- 

 fornia Depression is partially filled with late Miocene 

 or Pliocene Marine deposits, as determined by Kew. 

 Therefore, we may also conclude that the faulting 

 which produced that depression is of Miocene or earlier 

 age. It is not an unreasonable hypothesis to con- 

 sider it of the same age as the faulting of the Great 

 Basin Region. 



The marine Eocene and Miocene strata near Val- 

 yermo are downthrown several thousand feet into con- 

 tact with the granites of the Basement Complex, as 

 has been mapped by Noble, thereby testifying to the 

 past Miocene age of that portion of the rift, and 

 of the adjacent San Gabriel block of highlands. W. 

 H. English thinks the block is of Pleistocene age, and 

 I agree with him. 



Positive proof of the Pleistocene age of the San 

 Jacinto fault is the fact that it cuts definitely across 

 fossil-bearing Pliocene strata of the Badlands Range. 

 Strata of Eocene, Miocene and Pliocene ages are 

 found in the trough cr graben of the Elsincre 

 rift, thereby proving the Pleistocene age of that rift. 

 Slivers of Miocene and Pliocene sedimentaries are 

 found along the master rifts of the San Gabriel High- 



