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  

TOPOGRAPHY AND GENERAL GEOLOGY, 21 satisfactory for the basin of the Bear. The quantity of mining débris accumulated in the canyons of the Bear and its tributaries has twice been estimated with more care than was bestowed on similar deposits along the other rivers, and something is known also of the volume of the river’s piedmont deposit. When these estimates are considered in connection with the small discharge of the Bear and other factors affecting the ratio of the local arrest of débris to the total output of the mines, good reason is found to regard the estimate of 354,000,000 yards as excessive. As all the quantities involved in the discrepancy were subject to considerable uncertainty the adjustment was of the nature of a compromise and the share assigned to the output of débris was 100,000,000 yards, reducing the estimate to 254,000,000 yards. The only other stream to receive mining débris and convey it eventually to the Sacramento is the main branch of the Feather. Turner's estimates do not include the mines of its basin, and my own observations covered but a small area. In the report of the State engineer of California, Wm. Ham. Hall, for 1880, pages 23-24, estimates are made for the ‘water used and material washed out per annum” for the several river basins of the Sierra from the American northward. For the basin of the Feather the estimate of material washed is 12,687,500 cubic yards, and the sum of the estimates for the Yuba, Bear, and American is 36,480,500 cubic yards. Lieut. Col. Mendell makes a similar estimate for the year 1880,! in which the corresponding figures are 4,407,770 and 31,070,094. Mendell also gives with full detail the assessors’ returns of the water used in mining. Hall and Mendell both qualify their estimates— Hall because his data were incomplete and Mendell because the method used was unsatisfactory. In 1881 the canyons and mining regions of the Feather and Yuba were inspected by Marsden Manson, and his report? tends to discredit the estimates based on assessors’ returns. He found that much of the water ascribed to hydraulic mining was actually used in drifting and quartz mining and in other ways not involving the handling of large quantities of earth. Disregarding for the moment Manson’s implied criticism, accepting the estimates of Hall and Mendell, and assuming further that the total output of débris for the several basins for the whole period of hydraulic mining was proportional to the annual output, I have made two computations of the total output of the Feather. The figures quoted from Hall's table give 366,200,000 yards and the figures from Mendell’s table 186,600,000 yards. Various details reported by Manson and Turner, as well as data from other sources, indicate the probability that both these figures are excessive. On the other hand, a minimum estimate is suggested by the volume of the piedmont deposit of the Feather, which occupies the river bed between Oroville and Marysville. Hall estimated this, from surveys probably made in 1879, at 18,257,000 yards,? and the observations of Turner indicate that only moderate additions were made in the following decade. The suggested minimum is 40,000,000 yards, and this might serve as a practical estimate, so far as conditions of the lower river are concerned; but it would probably not be coordinate with the estimates for the other basins, which aim to show the full extent of the exploitation of the auriferous deposits. According to Manson the tailings from the greatest operations were chiefly lodged in a permanent way in the American Valley, an opening in the heart of the mountains. Between the limits 40,000,000 and 186,000,000 the value of 100,000,000 yards is arbitrarily chosen. Adding the estimate for the Feather Basin to that for the three basins farther south gives a total of 1,295,000,000 cubic yards as the output of the hydraulic mines on streams whose waters join the Sacramento. TERRANES OF THE EASTERN BORDER OF THE VALLEY. GENERAL FEATURES. Between the alluvium of the central valley and the first bedrock hills of the Sierra Nevada there lies, with flat westward dip, a series of formations ranging in age from the late Cretaceous deposits to those of the present time. Their occurrence and interrelations enable the observer to deduce with considerable certainty the geologic history of the western foot of the range. 1 Rept. Chief Eng. U. 8. Army, 1881, pp. 2486-2487, 2494-2501. 2 Rept. Chief Eng. U. S. Army, Lss2, pp. 2604-2612. 3 Rept. State Engineer, 1880, p. 11.