Mountains of the South 235 



flowed from higher lands and discharged their load of boulders, 

 gravel and sand at their mouths or on flat meadows or in basins. 

 These older fan deposits are technically called "fanglomerates." 

 They do not differ essentially from the alluvial fans that are 

 being deposited at the present time only as they may have been 

 deposited under different climatic conditions. Some fanglom- 

 erate deposits contain boulders of great size, carried from 

 adjacent heights by torrential streams such as occur from cloud- 

 bursts. Fanglomerate deposits are widespread over the San 

 Bernardino Range. They form an important feature of the 

 landscape, as they were formed during the time when the range 

 was being uplifted, and they are in many cases dissected by 

 streams which cross them due to the uplifting of the land. 

 Along the south front of the range recent movement has raised 

 the old fanglomerate floor more than 500 feet above San Gor- 

 gonio Pass. San Gorgonio River, Millard Canyon, Potrero 

 Creek, and Whitewater River have cut down through the fan- 

 glomerate to the level of the Pass. 



Rocks of the San Bernardino Range 

 Very Old 



The rocks that make up the formations of the San Bernar- 

 dino Range are, generally speaking, very old. Over much of 

 the mountain area the rocks now exposed at the surface are 

 granitic in character igneous intruded granite and meta- 

 morphic schists. These cover a large area south from San 

 Bernardino Mountain and from San Gorgonio Pass north and 

 east. North of San Gorgonio Mountain are considerable areas 

 of quartzite and limestone. The sedimentary formations are 

 very old, and have been much intruded by granite. Granites 

 are the most widespread rocks of the region. Nowhere are 

 there any considerable areas entirely free from intruded gran- 

 ites. Along the south flank of the San Bernardino Mountains 

 there are sandstones, shales, and fanglomerates of Tertiary and 

 Quaternary age. Remnants of basalt (lava) flows also occur 



