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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

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INTRODUCTION. 11 ” Tertiary stream beds—the ‘‘channels,’”’ as they are called—proved rich but difficult to mine. New methods were devised; by hydraulic mining the gravel banks were washed down by the aid of powerful streams of water, and by drift mining the bottoms of the old stream beds were followed by tunnels underneath the heavy volcanic covering. Millions of dollars were annually recovered from these Tertiary channels, and the heyday of this industry fell in the seventies of the last century. Since then, owing to the prohibition of hydraulic mining and the gradual exhaustion of the richer channels suitable for drift mining, the industry has slowly decayed until in the year 1908 the total production of the drift, hydraulic, and surface mines of the range, for the first time since 1848, fell below $1,000,000; indeed, this figure also includes the value of the gold washed from Quaternary gravels along the rivers. Gold is still contained in the Tertiary channels; miles of them are still unworked; but the problems are how to extract it without damage to other property from the débris and how to reduce the cost of drift mining so as to permit the exploitation of the less remunerative deep gravels. To compensate for this decay a new industry, that of dredging, has been developed along the bottom lands, where the present rivers emerge from their canyons and where fine gold has accumulated during Quaternary time on clayey or tuffaceous bedrock. During 1908 gold valued at nearly $7,500,000 was recovered by this method along the foot of the Sierra Nevada. ACKNOWLEDGMENTS. The work of the United States Geological Survey in the gold belt of California began in 1886 and was concluded about 15 years later. The extent of the topographic and geologic work is shown on Plate I. The examinations were begun by Mr. H. W. Turner and the author under the direction of Mr. G. F. Becker (from 1886 to 1892), and were later carried on independently, Mr. Turner mapping the north and south ends of the belt. Later Mr. F. L. Ransome contributed his share to the work in the Mother Lode folio and parts of the Sonora and Big Trees folios of the Geologic Atlas of the United States. At different times since 1884 Mr. J. S. Diller has worked in northern Plumas County and has added much to the knowledge of the gravels in this region, the result being embodied in the Lassen Peak folio and a number of other publications. A considerable part of the study of the ‘Tertiary gravels of the Sierra has fallen to the lot of the author because the most important gravel-mining districts were located in the area assigned to him. He has also at various times visited the principal districts outside of his area. However, a large proportion of the data in this volume have been taken from the folio texts and other publications of the geologists mentioned. The author is under the deepest obligation to these friends and coworkers, for without their help this volume would have lamentably lacked in completeness. Mr. G. K. Gilbert has very kindly permitted the publication in this volume of the results of his careful measurements of the quantities of gravel removed from the old hydraulic mines. The accurate and detailed investigations of Mr. Ross E. Browne on the Forest Hill divide and other districts have been of the highest importance and value in formulating the conclusions in these chapters. Messrs. J. D. Whitney, W. H. Pettee, and W. A. Goodyear were the pioneers in this field and their volume on the auriferous gravels is filled with painstaking and reliable information and has been a steady companion during the writer’s labors. The determinations of the fossil plants in the gravels by Messrs. Leo Lesquereux and F. H. Knowlton have been an invaluable aid in determining the geologic age of the gravels. Prof. Knowlton has kindly contributed to this volume a chapter on the present status of the Tertiary paleobotany of the Sierra. Heartiest thanks are extended to the many mining men who, by information and advice, have facilitated the collection of these data. Many of the photographs here reproduced were obtained through the cooperation of Dr. J. C. Hawv er, of Auburn.