LINUGUEN.] 



DEPOSITS IN GRIMES CREEK VALLEY. 



671 



! Sand and Gravel 



Fine Gravel 



worked in 1896, is illustrated in fig. 60. The bed rock is at the creek 

 level, and the work was done by means of hydraulic elevators, which 

 have been extensively utilized by this company. The gold, which is 

 generally of the size of mustard seeds, lies often on the higher bed 

 rock instead of in the potholes. The lower gravel carries all the gold. 



Older gravels. The low terrace 'separating Muddy and Grimes 

 creeks, one-fourth mile northwest of Pioneerville, and covered by 

 later bench gravels, is partly made up of granite, partly of an older, 

 somewhat cemented, granitic gravel. This belt is only about one- 

 fourth mile wide, and the gravel abuts against the granite on the 

 northern side, showing that it is separated from it by a fault. It is 

 evidently an older gravel sunk down along a fault-line. On the 

 southern side it apparently rests on granite. The same fault is well 

 shown in the creek on the eastern side, one-fourth mile above the 

 town. It is reported that a shaft 100 feet deep was sunk in this gravel 

 some twenty years ago, without reaching the underlying granite. The 

 gravel contains some 

 coarse gold. The side 

 hill immediately east 

 of this fault is wholly 

 composed of granite, 

 but above, on the nar- 

 row ridge separating 

 Grimes and Clear 

 creeks, lies a body of 

 somewhat similar 

 gravel, attaining an 

 elevation of 200 feet 

 above the creek. Gran- 

 ite bed rock is found 120 feet above the creek, and on it rests a 

 bed of coarse gravel containing some gold. Much of this gravel has 

 been worked by the hydraulic process. 



Lake beds. ~No extensive areas of lake beds occur in this vicinity, 

 but in the valley of Muddy Creek, 2 miles north of Pioneerville, a 

 small patch of a rather remarkable deposit is found. For a distance 

 of a mile the creek runs in a narrow canyon, which then opens to a 

 somewhat wider valley. Here lie, chiefly along the western side of 

 the creek, beds of soft white sands, gravels, and clays, with a little 

 lignite. In one place where the stratification could be made out the 

 layers seemed to dip 20 W. This small mass of sedimentary deposit 

 has a lacustrine character, and should probably be correlated with the 

 lake beds of Idaho City; it does not contain any gold, but the surface 

 gravels resting on it are said to have been unusually rich, the softer 

 beds having acted as riffles, catching the gold. On all sides the 

 granite rises rather steeply. At Bummer Hill, one-half mile above 

 Centerville, a granitic sand, which may possibly also belong to this 

 lacustrine series, forms the bed rock. 



FIG. 60. Bank of bench gravels one-fourth mile north of Pio- 

 neerville, level of Grimes Creek. 



