

BED-BOCK: SOUTH OF THE MOKELUMNE RIVER 



121 



the gravel deposits, although numerous and often rich, are on too small 

 a scale and too " spotted " to be capable of being attacked with success by 

 hydraulic mining operations on a large scale. 



In describing the geology of the region south of the Stanislaus we may 

 follow an order somewhat similar to that already indicated for the region 

 farther north. 



■v 



§ 1. The Bed- Rock in Calaveras, Tuolumne, and Mariposa. 



So much has already been stated in regard to the bed-rock in Tuolumne and 

 Mariposa* that this branch of the subject may be passed over with rapidity. 



The most interesting orographical feature of this region in connection 

 with the bed-rock series is, the existence of a subordinate range in the 

 foot-hills, parallel with the Sierra, but having more of an isolated and inde- 

 pendent character than any other of the more or less continuous foot-hill 

 ranges which lie along the base of the great mass of the Sierra itself. The 

 range in question is so distinctly marked as to have received a name, and 

 the group is known as the "Bear Mountains." It is, in fact, a double ran^e, 

 having two quite well-marked divisions 5 the more southwesterly, which is 

 parallel with the other but quite subordinate to it, is known as the " Gopher 

 Hills/' A glance at the map of Central California will show the position of 

 these elevated ranges. They extend between the Calaveras and the Stanis- 

 laus rivers, and govern the distribution of the drainage within that 

 giving it a character quite unlike what it usually has in this part of the 

 Sierra. The various streams which rise in the upper portion of Calaveras 

 County How with the usual southwesterly course, until they reach the north- 

 east edge of the Bear Mountains, when they turn at right angles, and flow 



■ 



northwest and southeast to the Calaveras or the Stanislaus. The 

 creeks, which rise in the rather broad and regular valley between the Gopher 

 Hills and the Bear Mountains, also have courses parallel to that of the 

 ranges themselves. 



The rocks of the Bear and Gopher ranges are all of the bed-rock series, 

 and highly mctamorphic. The slates are well developed in the depression 

 between the two ranges, and are there associated with irregular bands of 



remon 



smaller 





serpentine which are sometimes of great length and width. 



This region 





was formerly the scat of the most active copper-mining operations in the 

 State, Copperopolis being the principal mining centre. The only important 



* See ante, pp. 43 - 47. 



