SCIENTIFIC BACKGROUND 185 



Solomon Ranges. Sometimes the folding is compact 

 and complicated. In one instance which may be seen 

 in Kew's cross-section of Ventura County, the folds of 

 certain ranges are overthrown (recumbent) and fault- 

 ed along horizontal planes (overthrust). 



In some instances narrow belts, or ribbon-like slivers 

 of sedimentary rocks may be preserved along fault 

 lines in the granitic highlands. Instances of this kind 

 occur in the northeastern and southeastern portions 

 of the San Gabriel Highland as mapped by Noble and 

 Kew respectively, and in the San Bernardino Plateau 

 as mapped by F. C. Vaughan. Such occurrences may 

 be the structurally elevated and degraded remnants of 

 former folds, from which the once overlying mass of 

 sedimentary rocks has been removed by erosion. The 

 close relationship of the folds and faults is further 

 shown by the fact that open folds may sometimes 

 change with time and continued pressure into compact 

 ones. 



THE DOMINGUEZ RANGE 

 The Dominguez Range, previously described, may be 

 taken as the simplest type of a recent mountain fold. 

 Although not entirely so, it is practically a continuous, 

 elongated, anticlinal fold with subordinate domes and 

 sags in link-like succession along it. In places the 

 continuity may be slightly broken with offset ends ar- 

 ranged en echelon. The uppermost strata involved in 

 the arching at the surface are of Pleistocene age, so 

 that we may conclude that the range originated either 

 in late Pleistocene or Recent time. It was in late 

 Pleistocene time, as I show by evidences elsewhere 

 herein given. In general, cross-sections reveal the 



