LINDGREN.] GRAVELS OF GRANITE CREEK. 673 



being 20 to 30 feet above the creeks and that of the higher one at an 

 elevation of 50 feet. Near Granite and Placerville bowlders of por- 

 phyritic rocks are abundant. The benches opposite Granite also con- 

 tain many basaltic bowlders and pebbles, which are probably derived 

 from the basaltic areas high tip on the summits of the Boise Ridge, 

 referred to later. On the broad flood plain of Fall Creek the bench 

 gravels are very extensive, and reach an elevation of 4,380 feet above 

 the sea, or 50 feet above Fall Creek. All of the benches along Granite 

 Creek and its tributaries from the northeast have been worked for 

 gold. 



Older gravels. Near Placerville and Granite are several very inter- 

 esting occurrences of gravels belonging to a stream system which dif- 

 fered considerably from the present one and giving evidence of having 

 undergone disturbances since their deposition. Two small and iso- 

 lated gravel patches occur close together one-fourth mile northwest of 

 Placerville, on Sailor Gulch. Each contains but a few acres. Both 

 have been worked by the hydraulic process. The exposures show a 

 30-foot bank of medium-sized gravel with excellent fluviatile stratifi- 

 cation. The gravel contains a great number of porphyry bowlders 

 similar to the rock cropping near Quartzburg. The granitic bed rock 

 slopes gently westward, and extends down to the present creek. The 

 bed rock is 150 feet above the level of Wolf Creek at Placerville. A 

 small area of similar gravel lies at the same elevation near the Pio- 

 neerville road, 1 mile east-northeast of Placerville. 



Opposite Placerville lies the Ranch Company's claim, which has 

 been extensively washed of late years and has produced much gold. 

 This is a mass of older, compact gravels resting in a channel-like 

 depression, and on which, along the creek, the later bench gravels 

 have accumulated. In the early years this gravel was considered 

 "false bed rock," and it was not generally supposed that it could be 

 profitably worked. The gravel body lies on the ridge separating 

 Boyles Gulch from Wolf Creek, the top of it being one-fourth mile 

 wide and reaching an elevation of 200 feet above the level of the tail- 

 ings at Placerville. It fills a depression or channel, the bed rock ris- 

 ing rapidly northward and southward. The lowest bed rock is exposed 

 in the present diggings, and is at the bank 75 feet above the tailings 

 at Placerville, sloping from there gradually down to the debris-filled 

 stream-bed at the rate of 6 feet per 100 feet. The character of the 

 gravel is shown in fig. 61. The gravels bear every evidence of having 

 been accumulated in a stream of considerable size. They are coarse 

 at the bottom, very well rounded, and contain abundant cobbles of 

 the peculiar altered porphyry occurring near Quartzburg. No basalt 

 bowlders were found. The gold is fine and evenly distributed through 

 the mass of the low r er gravel. On the eastern side of the ridge there 

 are also hydraulic pits, and the deepest bed rock lies 135 feet above 

 the creek bed at Placerville. At this point the channel suddenly 

 18 GEOL, PT 3 43 



