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  

196 TERTIARY GRAVELS OF THE SIERRA NEVADA OF CALIFORNIA. are but sparingly represented in this area. Although the Quaternary gulch and stream gravels below the Mother Lode were rich, it so happens that no important Tertiary streams crossed the most productive parts of the Mother Lode. The most prominent gravel areas are located at Mokelumne Hill, Valley Springs, San Andreas, Altaville, Vallecito, Douglas Flat, Columbia Hill, and from Railroad Flat to the Sheep Ranch mine. Of these the gravels at Mokelumne Hill were doubtless the richest. The production of placer gold has steadily dwindled until lately, when dredging operations were begun. With careful management many gravel channels as yet untouched would probably give good returns. There is some hydraulic ground, but the late operations have been confined to drifting. In 1905 Calaveras County produced $302,000 in placer gold. About $203,000 of this sum was derived from dredging operations in modern streams. One of these dredges is located near Camanche, on the lower Mokelumne, and the other at Jenny Lind, on the lower Calaveras. Mokelumne Hill produced $16,000, chiefly from drifting; San Andreas $55,000, from one hydraulic and one drift mine; and Douglas Flat and vicinity a few thousand dollars. The county contained 2 dredges, 3 hydraulic mines, 9 drift anes and 10 surface mines, not counting the small operations of the Chinese. Amador County in 1905 produced only $49,000 in placer gold; most of this came from Chinese operations. The production of the placer mines of Tuolumne County in 1905 was only $13,394. In 1909 the production of placer gold from Amador County in the Jackson quadrangle was $41,800, derived from a great number of small drift and sluice mines at Oleta, Volcano, and Lancha Plana. In the part of Calaveras County contained in the same quadrangle the yield was $257,000, distributed about as follows: Placer gold produced in part of Calaveras County within Jackson quadrangle, 1909. Dredging near Jenny Lind and Wallace......2-.. 20.20. e eee cece eee eee eee ence $212, 000 Valley Springs.....-..00 22. e eee eee ce ce eee ee teen eee ee tee tence cence eect eeeee 1, 200 San Andreas, Fourth Crossing, etc........ eee eee eee eee eee e es eee eeeeeas 10, 000 Mokelumne Hill (mainly drift mines).........2 0.202022 cece eee eee eee cece eee 11, 600 Railroad, Flats issssswsseres ss ss ox ewaeenic oo as eaaeweatee ss os eee eo oe See R RR Fe eee 9, 600 Small arid scattered: scccsssoweesemecwis.ae ss 5 ESBS RG & Ss ESR SERG YS 22 5 + 55.58 Fniede ce ens 12, 600 257, 000 The Big Trees quadrangle has a comparatively small placer production, approximately . $8,800 in 1909, distributed as follows: Placer gold produced in Big Trees quadrangle, 1909. Calaveras County: Douglas Flat and Vallecitos: scsces saa os ss eww wewews ss i seeueeeew cee ssa gees eewee ses aces $2, 300 Sheep Ranch and Murphy........20. 220022 e cee ce eee ee eee eee eee ee eee 1, 900 Tuolumne County: Columbia Basin.......0. 022 cece eee e eee e ence eees 4, 600 8, 800 OUTLINE OF TERTIARY HISTORY. The Tertiary record of deposition of this district has been established most carefully by H. W. Turner. The earliest deposits are prerhyolitic river gravels, but there are only small amounts of such material in the old river channels. During this epoch, which probably corresponds to the earliest Tertiary, the boundary between the ‘‘ Bedrock series” and the superjacent formations was probably situated many miles farther west than now. Then followed in middle Tertiary (Miocene) time the transgression of the Ione formation up to present elevations of about 1,000 feet, indicating a considerable submergence underneath the brackish waters of the gulf which then ceeupied the great valley. This formation attains its maximum development in the Jackson quadrangle. The lower portion of the series, 4 Jackson folio (No. 11), Geol. Atlas U. S., U. S. Geol. Survey, 1894. .