



-- — ~ - *-«-«» 



48 



THE AURIFEROUS GRAVELS OF THE SIERRA NEVADA. 





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Gravel Formations of Placer and Amador counties, additional details will he 

 found for that district ; so also for the region still farther north such facts in 

 regard to the lithological character of the bed-rock will be introduced as 

 may seem to be required, when speaking of the overlying cletrital masses. 



An approximation to the order of succession of the various groups of the 

 bed-rock series in the region between the Merced and the Stanislaus may 

 also be traced nearly or quite through the whole extent of the auriferous 

 belt from Calaveras to Plumas County. There is, in general, near the foot- 

 hills, a thoroughly metamorphosed belt of rock, made up in part of sedimen- 

 tary and in part of volcanic materials ; then, extending through the central 



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portion of the auriferous series, a band of a much more decidedly slaty rock, 

 considerable portions of which are very finely laminated. A large part of 

 this rock is argillaceous in character ; but some of it is talcose, and it has, 

 in places, a good deal of rather fine-grained sandstone interstratified with it. 

 There are also extensive masses of serpentine found in this connection. 

 Although the Great Quartz Vein cannot be positively identified any farther 

 than the middle of Amador, yet it is pretty evident that this slaty formation 

 is decidedly the most auriferous portion of the bed-rock series, and it abounds 

 in quartz veins, many of which contain more or less gold. Above the slate 

 belt proper the rocks are very varied in lithological character ; but, on the 

 whole, as in the region between the Merced and the Stanislaus, decidedly 

 more quartzose than farther down the slope. The limestone, or marble, 

 shows itself in many places, nowhere continuous for any great distance be- 

 yond Calaveras County, and nowhere to the south of Pence's Ranch, in Butte 

 County, showing any indications of fossils, so far as yet known. From Mari- 

 posa through Tuolumne into Calaveras County, the limestone outcrops, when 

 laid down on the map, make a tolerably continuous line, which keeps pretty 

 near the edge of the granite, or well towards the upper portion of the aurif- 

 erous belt Through the counties north of Calaveras it is difficult to trace 

 any regular order in the limestone bands, which are usually quite short and 

 irregular in form. There are, however, indications of the former existence 

 of two continuous belts of this rock ; one near the granite, the other low 

 down near the base of the Sierra. 



A few words may here be introduced in regard to the structural relations 

 of the bed-rock series, although this subject is not one which properly comes 

 within the scope of the present volume. It may be stated, without hesitation, 

 that the problem is an extremely difficult one. And it is not likely that it 





