PHYSICAL GEOGRAPHY 85 



THE MASTER HIGHLANDS OF THE 

 TRANSVERSE BELT 



In this paper we are using the term Master High- 

 lands for those larger and higher mountain units of 

 California which stand conspicuously above their 

 surroundings. These are mostly composed of granite 

 and metamorphic rocks of the Basement Complex, 

 from which vast thicknesses of previous coverings of 

 sedimentary rocks must have been eroded. In this 

 category we place the Sierra Nevada Cuesta and its 

 southwest extension, the Tehachapi Plateau, the San 

 Gabriel and San Bernardino Highlands of the Trans- 

 verse Belt, and the San Jacinto, Cuyamaca and other 

 highlands of the Peninsular Plateau and, in fact, all of 

 the last mentioned features. 



These Master Highlands are not structural folds, 

 but are apparently great, horst-like, upthrust blocks, 

 the summits of which, as particularly exemplified by 

 the San Bernardino Highland, are remnants of a for- 

 mer lowland peneplain which has been checkerboarded 

 by fault lines, and the segments thereof later uplifted 

 or depressed to various heights into the master high- 

 lands or the valley plains. Of course there are many 

 other details, but we are not dissecting them with a 

 scalpel. 



Of the above mentioned, the San Gabriel and San 

 Bernardino Master Highlands are the most conspic- 

 uous members of the Transverse Belt. Each con- 

 sists of an elongated, summit-area of one or more great 

 polygonal fault blocks which have been floated upward 

 from ten to fifty thousands of feet between fault line 

 borders. This estimate includes the thickness of sedi- 



