File:Annual report of the United States Geological Survey to the Secretary of the Interior (1895) (14594855407).jpg

Identifier: annualreportofun1711geol (find matches)
Title: Annual report of the United States Geological Survey to the Secretary of the Interior
Year: 1880 (1880s)
Authors: Geological Survey (U.S.)
Subjects: Geological Survey (U.S.) Geology Water-supply Forest reserves Mines and mineral resources
Publisher: Washington : G.P.O.
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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er is next to be seen aboutLava Peak, and then on the spur south of Long Valley ( reck, some ofthe gravel at the latter locality having an elevation of only 5,000 feet.At the north end of the Mohawk Lake beds is an area of well-roundedgravels, composed of pebbles of the pre-Cretaceous rocks. This depositrests, where surely in place, on the auriferous slate series. The lowaltitude (about 4,500 feet) of a portion of this gravel at the mouth ofCedar Creek is probably due to landslides, for where it is certainly inplace on the ridge south of Cedar Creek the maximum elevation is5,500 feet, extending down the ridge slope (easterly I to near the 5.000-foot contour. A tunnel by the Feather River at the mouth of CedarCreek has been run in to strike this gravel channel, but if landslideshave occurred here, it is evident that the tunnel is much too low I. loofeet). The tunnel, according to a miner at work there, was L,800 feetlong in 1890, and was in hard lava all the way. The hard lava referred
Text Appearing After Image:
TURNER.) GRAVEL DEPOSITS. 611 to is the andesitic breccia that forms the bed and walls of the river inthis vicinity. A shaft was sunk on the hill top 500 feet above and eastof the tunnels mouth. It is said that this shaft was in gravel for itsentire depth, or 375 feet. As indicated above, however, all of thegravel below the 5,000-foot contour is believed to be out of place. Thisclownthrown material is, however, not all gravel. There is some ande-sitic breccia mixed with it. Numerous rhyolite bowlders and pebblesindicate an area of that rock in the vicinity now eroded or coveredover. The presence of these rhyolite pebbles would seem to indicatethat a portion of this gravel is of later age than that of the HaskellPeak channel, which is capped with rhyolite. So far as could be made out, the Cedlr Greek river gravel is in im-mediate contact on the south with the Pleistocene Mohawk Lake beds.The deposits of the old river channel just described, extending fromnorth of the fortieth parallel

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