Geology topics
Publications and source records attributed to Allan B. Griggs.
This dataset was digitized by the U.S. Geological Survey EROS Data Center and U.S. Geological Survey Spokane Field Office for input into an Arc/Info geographic information system (GIS). The digital geologic map database can be queried in many ways to produce a variety of derivative geologic maps.
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The Coeur d'Alene district, near the base of the northern panhandle of Idaho, is one of the world's larger lead- zinc and silver-producing areas. The greater part of the dis~rict i~ included within five map areas, from east to west the Pottsville, Mullan, Wallace, Kellogg, and Smelterville, which were geologically mapped during this study. These quadrangles encompass an area about 26 miles long in an east-west direction and about 9 miles wide. The district lies wholly within the Coeur d'Alene Mountains, the part of the Bitterroot Range that is drained by the Coeur d'Alene River. The Bitterroot Range is a rugged, deeply dissected mountain mass which extends on both sides of the Idaho-Montana boundary for more than 200 miles and is a part of the Northern Rocky Mountains; within the district the range has a relief of 3,000-4,000 feet. The westward-flowing South Fork of the Coeur d'Alene River bisects the district, and roads along this river and its major tributaries generally provide easy access to the communities and many mines.
This report pt·esents a description of the stratigraphy, structure, and petrology of the volcanic rocks of the central and northern parts of the Western Cascade Range of Oregon. The study is a part of a long-range cooperative program between the U.S. Geological Survey and the Oregon State Department of Geology and Mineral Industries to prepare a geologic map of Oregon. The map area, about 7,500 square miles, lies in the densely forested western slope of the Cascade Range. It is bounded approximately by lat 43° N. and lat 45°30' N. on the south and north, the crest of the range on the east, and long 123° W. and the edge of the Willamette Valley on the west. The geology, which was mapped by reconnaissance methods, is chiefly based on examination of rock exposures along roads. The Cascade Range in Oregon comprises two physiographic divisions: the Western Cascade Range, which includes a wide, deeply dissected belt of volcanic formations making up the western slope of the range, and the High Cascade Range, which includes chiefly younger cones and lava flows forming the nearly undissected crest of the range. The volcanic rocks of the Western Cascade Range are deformed and partially altered flows and pyroclastic rocks that range in age from late Eocene t·o lute Miocene, as determined chiefly from fossil plants from more than 50 localities. These volcanic rocks overlie or interfinger westward with marine sedimentary rocks, and in the southwestern part of the map area they overlie pre-Tertiary plutonic and metamorphic rocks of the Klamath Mountains.
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