L1NDGKEM.] 



LAKE BEDS OF MOORE CREEK VALLEY. 



665 



It forms a bench-like deposit 175 feet above the creek, and the larger 

 part of it has been worked by the hydraulic process. 



Lake beds. Near Idaho City, on both sides of Moore Creek, a con- 

 siderable area is covered by soft sedimentary beds of clay, sand, and 

 gravel. These do not bear evidence of being river deposits. The 

 regular stratification and their general character indicate that they 

 have been deposited in a body of water, in all probability a fresh- 

 water lake. These beds do not contain any notable amount of gold, 

 but the fluviatile auriferous gravels just described are deposited on 

 their eroded surface. The dip of the beds proves that that they have 

 been disturbed since their deposition. Recognizing their sedimentary 

 nature, the miners call these lake beds "false bed rock." The lake 

 beds are first met with 1 mile below Warm Springs, where they appear 

 as semiconsolidated white sand and clays. Near Warm Springs they 

 assume the form of coarse yellowish sandstones, evidently cemented 

 by the opaline silica of the hot waters. In fact, sandstone cemented 



Auriferovs Gravel pa rHy washed off 





FIG. 58. Exposure of lake beds and auriferous gravel 1J- miles south of Idaho City. Top of 

 gravel, 400 feet above Idaho City. 



by fire opal has been collected on both sides of the creek, and the 

 occurrence is mentioned by Mr. S. F. Emmons. 1 Owing to the very 

 coarse character and rapid accumulation of the debris the stratifica- 

 tion is poorly preserved. Half a mile below the hot springs these sand- 

 stories form a bluff 300 feet high, and also extend east of the road, 

 producing a relatively narrow passage for the creek. A slide has 

 taken place near the creek, covering an older channel, the bed rock of 

 which lies only a few feet above the present creek and which has 

 been mined by several tunnels. At Turner's claim the lake beds form 

 the bed rock and are well exposed. They dip 5 NW. and consist of 

 soft sand and clay with occasional coaly layers. The clay encloses 

 nodules of iron pyrite containing some gold and silver. 



Near Turner's claim a projecting spur of granite reaches to within 

 a few hundred feet of the road, and in the hydraulic cuts the lake 

 beds are seen to rest on it. Between Turner's claim and the citv the 



1 Boise Statesman, March 29, 1896. 



