Vol. 4] 



Lawson. — Tehachapi Valley System. 



457 



extent is 5^ miles. The valley thus bounded contains about 13 

 square miles. There are two principal lines of drainage through 

 the valley. One of these is a stream that comes into the valley 

 at its southeast corner from a high grade canon in the mountain 

 on the south. This stream has built up an extensive alluvial 

 cone which spreads out over almost the entire valley. The drain- 

 age from Brites Valley shirts the northwest edge of this alluvial 

 slope and catches part of the water that flows down the slope 

 of the fan. The entire drainage of the valley converges on its 

 southwest corner and after flowing for a short distance over a 

 bedrock platform enters a narrow gorge and drops rapidly to 

 the Tejon Valley. This gorge descends about 2500 feet in a dis- 

 tance of 4 miles. In the northern part of the valley this alluvial 

 fan meets the waste slope from the southwest scarp of Bear 

 Mountain, and it is the trough between these two opposing slopes 

 which determines the path of the stream from Brites Valley for 

 the first two miles of its course. Beyond this it is crowded over 

 well toward the base of the hills on the northwest side of the 

 valley. The valley thus largely occupied by alluvium is an 

 artesian basin, and in the middle part of the valley a well has 

 recently been sunk to a depth of 125 feet which yields a flow 

 of water at the surface. The mouth of this well is but little 

 above the rock platform over which the drainage flows before 

 escaping from the valley. The well, therefore, proves that the 

 valley, independently of the alluvium which fills it, is a rock 

 rimmed basin. The rocky platform at the southwest corner of 

 the valley is a most interesting feature. It extends out from the 

 base of the hills which bound the valley on its northwest side a 

 distance of half a mile and appears to pass under the feather 

 edge of the alluvial fan with a uniformly flat slope, as is indi- 

 cated by occasional protuberances of rock for some distance 

 within the area of the alluvium. This platform is interpreted 

 as a surface of stream abrasion and is correlated hypothetically 

 with the similar stream-cut terraces above described, in 

 Tehachapi and Brites Valleys. This platform probably extends 

 as a flanking terrace, but thinly veneered with alluvium, along 

 the greater part of the northwest side of the valley. The hills 

 ■ which rise above the valley on this side harmonize with this 



