2 24 JOHN S. BROWN 



The southernmost fault scarp of this series was observed in 

 Canebrake Canyon, and at Agua Caliente Springs. At both places 

 the mountain front for several hundred feet from the lowland bor- 

 der consists of rotten, grayish granite, broken into minute joint 

 blocks, kaolinized, and altered. Farther in the interior of the 

 mountains the rock is dense and unweathered. There is much 

 evidence of hydrothermal alteration, a very natural thing to expect, 

 at Agua CaKente Springs, where a large number of springs, part 

 of which yield warm water, issue from the granitic rocks. 



Cutting across this first system of faults is a system which 

 strikes approximately N. 45 W., and which is represented by several 

 prominent faults. The most northerly fault of this system is the 

 San Jacinto fault, which passes south and west of San Jacinto 

 Mountains, extending through Hemet Valley and down Coyote 

 Canyon. For several miles it traverses the northeast side of Borego 

 Valley.^ The uplift along this fault was on the northeast. Coyote 

 Mountain on the northeast of Borego Valley is part of a prominent 

 spur elevated in this upKft, and is bordered on the southwest by 

 well-defined scarp, which displaces Tertiary beds. It is probable 

 that the San Jacinto fault extends at least as far as Borego Moun- 

 tain, but it is much obscured in that direction by recent alluvial 

 deposists. Movement occurred along this fault at the time of the, 

 San Jacinto earthquake of 1899. 



Several faults which have been recognized in the vicinity of 

 Warner Valley^ extend southeastward into the western part of this 

 region. One of these which passes nearly through Warner Hot 

 Springs traverses Grapevine Canyon, turns nearly east along a part 

 of San Felipe Creek, and disappears near The Narrows. Its uplift 

 was on the northeast, and the tongue of granitic rock south of 

 Borego Valley and in the vicinity of The Narrows is believed to 

 have originated from the upHft. A fault extends from Warner 

 Valley down the headwaters of San Fehpe Creek, and its eroded 

 scarp forms the northeast side of San Felipe Valley, being a promi- 



' H. W. Fairbanks, California Earthquake Commission Report, Carnegie Inst, of 

 Wash., 1910, p. 47. 



2 A. J. Ellis, and C. H. Lee, "Geology and Ground Waters of the Western Part of 

 San Diego County, Cal.," ^7.5. Geol. Surv. Water-Supply Paper 446. 



