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U.S. Geological Survey Geologic Investigations Series Map I–2542

Geologic Map of the Red bluff 30’ x 60’ Quadrangle, California

By M.C. Blake, Jr., D.S. Harwood, E.J. Helley, W.P. Irwin, A.S. Jayko, and D.L. Jones

Thumbnail of and link to report PDF (9.3 MB)Introduction

The Red Bluff 30’ x 60’ quadrangle includes rocks of four major geologic provinces: the Klamath Mountains, the Coast Ranges, the Great Valley, and the Cascade Range. These rocks and their geologic histories differ greatly from one another. The Klamath Mountains are mainly an accumulation of large tectonic slices of oceanic crust, upper mantle, and volcanic island arcs that range in age from early Paleozoic to Late Jurassic. The rocks of the Coast Ranges present in the Red Bluff quadrangle consist of oceanic crustal rocks that are somewhat similar lithologically to those of the Klamath Mountains but are Early Jurassic to Cretaceous in age. The Great Valley province includes a thick deposit of moderately deformed Jurassic and Cretaceous marine strata that consist of detrital materials derived from uplifted basement rocks of the Klamath Mountains and the Sierra Nevada. In the western foothills of the Sacramento Valley, these strata rest partly on the Coast Range ophiolite and partly on the Klamath Mountains basement rocks and thus pose a complex tectonic question. In the central part of the Sacramento Valley, a mantle of Tertiary and Quaternary detrital continental deposits overlies the Great Valley sequence; these deposits, which are derived from the west, grade eastward into coeval volcanic materials derived from the Cascade Range province. The stratigraphic and structural relations shown on the map provide a key to understanding how the rocks of these various provinces were formed and were subsequently assembled.

Last modified October 19, 2012

First posted November 3, 2000


  • Readme TXT (8 kB)
  • Metadata TXT (78 kB)
  • GIS database ZIP (13.9 MB, compressed; 57.5 MB, expanded) This GIS database contains all the geologic information used to publish the map.
  • Stratagem font package ZIP (545 kB, compressed; 635 kB, expanded) Stratgem fonts used to represent geologic unit labels in ArcInfo for this map.
  • This report is also available in print from:

    USGS Information Services, Box 25286,
    Federal Center, Denver, CO 80225
    telephone: 888 ASK-USGS; e-mail:

For additional information:
Contact Information, Western Region Geology and Geophysics Science Center—Menlo Park
U.S. Geological Survey
345 Middlefield Road, MS-973
Menlo Park, CA 94025-3591

This report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Blake, M.C., Jr., Harwood, D.S., Helley, E.J., Irwin, W.P., Jayko, A.S., and Jones, D.L., 1999, Geologic map of the Red Bluff 30' x 60' quadrangle, California: U.S. Geological Survey Geologic Investigations Series Map I–2542, 1 sheet, scale 1:100,000, pamphlet 15 p., and database, available at

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