1922] Vaughan: Geology of San Bernardino Mountains 



397 



Extending southeast from the mouth of Blackhawk Canon nearly 

 to Rattlesnake Canon there is a scarp as prominent as that to the west 

 (pi. 23A). Because of its resemblance to the other and the fact that 

 the line of uplift could hardly stop short, this also must represent a 

 fault. Its eastern limit is poorly defined due to the degradation of the 

 scarp. 



It seems that there has been a rather recent uplift along the north 

 front of the hills near Two Hole Springs. To the south a straight wall 

 of granite and schist rises, but on following this westward a mile 

 beyond Rattlesnake Canon a large alluvial fan is found to be broken 

 along the same line with uplift on the south. The upper portion of 

 this fan extends southeastward into the hills and was evidently the 

 mouth of Rattlesnake Canon in former times. It is now being rapidly 

 dissected, but its original features are still preserved and the break 

 along the north flank is still clear (pi. 23A). 



From Rock Corral a scarp extends to the southeast beyond the 

 limits of the quadrangle and to the northwest two miles beyond Old 

 Woman Springs. The stream channels on the plateau southwest of 

 Rock Corral pursue very tortuous courses until they nearly reach the 

 top of the escarpment, where they plunge down precipitously. This 

 discordance is equally clear southeast of Old Woman Springs, where 

 a flat bench of granite and basalt rises suddenly above the desert floor. 

 Old Woman Springs are on this line and the water from them is warm, 

 about 20° C. While this temperature is not very high, it is sufficient 

 to indicate a deep source such as a fault might tap. Another spring 

 is found on the same line about a mile northwest of Old Woman 

 Springs. All this evidence is in agreement and points to the same 

 thing : the scarp is the result of a movement on a fault. 



It is interesting to note that in the desert there are several faults 

 parallel to that just described. One of these extends from Box S 

 Springs northwestward beyond Rabbit Springs. That this is a fault 

 is suggested by the numerous springs located along the line. Further- 

 more, the physiography shows a slight uplift on the southwest side. 



Another scarp extends along the northeast of the long hill six miles 

 northeast of Old Woman Springs. The southwest approach to this 

 hill is very gentle, but on the northwest it presents a steep granite 

 wall. It is also of importance to note that this lines up with another 

 long hill six miles farther southeast and with a group of hills three 

 miles south of Means Wells. These last also have a gentle approach 

 from the southwest, but drop off steeply on the northeast. Besides 



