Collection: Books and Periodicals

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Title: The Tertiary Gravels of the Sierra Nevada of California by Waldemar Lindgren (1911) Collection Type: Books and Periodicals Source(s): Google Books # of Pages: 301 Download PDF: User Login Required Download OCR Text: User Login Required

Date Scanned: 2024-07-14 06:26:22 Item Sourced From: PDF First Created: 2025-03-17 05:53:20 Last Updated: 2025-03-17 05:53:20

Original Held At: Searls Historical Library Location: 161 Nevada City Hwy, Nevada City, CA 95959

Page: of 301  

COLFAX QUADRANGLE, 153 short distance. Again entering the Colfax quadrangle, it must continue below the volcanic masses in a northeasterly direction. Its identity with the channel of French Meadows and Soda Springs (in the Truckee quadrangle) is indicated beyond all doubt. At no place between Ralston’s and Soda Springs, however, is the bottom of the channel exposed. There appears to be but little prevolcanic gravel on the Long Canyon divide. Most of the gravel is interstratified with rhyolitic tuffs, forming a series 160 feet thick at Ralston’s and at least 250 feet thick at Blacksmith Flat, 4 miles to the east on the southern slope of the ridge, where the bedrock elevation is 3,800 feet. Hydraulic operations have been carried on successfully to some extent at Ralston’s and at Blacksmith Flat. The gravel everywhere contains granite bowlders, indicating that the stream came from the higher part of the Sierra Nevada. At many places along the south rim in Long Canyon, northeast of Blacksmith Flat, small mining operations have been carried on. At Russian Ravine the surface gravel was hydraulicked with excellent results. In addition to those at Ralston’s, small operations have been carried on in Brushy Creek, at the north side of the ridge, and also at a point 14 miles north of Russian Ravine. At the Jatter place, at an elevation of about 4,500 feet, it is believed that an inlet exists near the point where the tributary from Duncan Peak entered the Long Canyon channel. The gravel at this place is 150 feet thick and contains large bowlders of quartz and metamorphic rock. It is covered by heavy masses of rhyolitic tuff. The gold in the gravels embedded in the rhyolitic series is generally fine. Extensive prospecting operations of recent date dhiave that the main channel on the Long Canyon divide is broad and flat and that the gravels cover large areas but are generally of low grade. Intervolcanic channels do not seem to exist. Hydraulic operations were in progress in 1891 at Ralston’s (Pat Goggin’s mine) and at Lynchburg, about 3 miles to the southeast, on the southern slope of the ridge. , CONNECTIONS OF THE CHANNEL SYSTEMS. The general Neocene drainage system of this quadrangle has been roughly considered (pp. 134-135), but it remains to indicate in a more detailed way the connections of the channels of the southern part of the area with those of the region between Dutch Flat and North Columbia. A river corresponding roughly to the present Middle Fork of the American had its source near Castle Peak, in the Truckee quadrangle, thence flowed across to Soda Springs and approximately followed the course of the present Middle Fork, entering this quadrangle along the line of the present ridge between Long Canyon and the Middle Fork and at the southern portion of this ridge curving into the Placerville quadrangle. It reentered the Colfax quadrangle a few miles farther west, and the channel emerges from under the volcanic capping at Ralston’s. A tributary from the Duncan Peak region joined it with a general southerly direction. From Ralston’s much of the channel is eroded, but it may be regarded as certain that the main channel continued westward, touching Michigan Bluff and Sage Hill and here receiving an important tributary running nearly due south from Damascus. The deposits of this tributary channel are preserved below the lava ridge between Damascus and Gas Hill. Near Gas Hill it received a tributary from Last Chance and Deadwood. East of Michigan Bluff the channel is eroded, but its continuation is found at Bath, whence the main channel ran through to Mayflower. Here it made a wide curve and ran southward to Forest Hill and Dardanelles. Thus far the general course is outlined without uncertainty, but from this point on the difficulties begin. The main channel is broad and well defined and is marked by its heavy deposits of gravel and clay. Under the southwestern prolongation of the Forest Hill lava ridge nothing has thus far been found which would indicate that the main old river flowed down in this direction. It is true that a narrow channel of the intervolcanic epoch extends down in this direction, but the intervolcanic channels were notably independent of the older and main drainage basins, being excavated after a large part of the old river basins had been filled by accumulations of silt and volcanic mud, and probably also after the tilting of the Sierra Nevada had taken place. Their direction thus affords no criterion of the prevolcanic drainage lines. It would certainly seem as if some fragments of the accumulations of the old