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U.S. Geological Survey Open-File Report 2012–1228

Digital Geologic Map of the Redding 1° x 2° Quadrangle, Shasta, Tehama, Humboldt, and Trinity Counties, California

By Luis A. Fraticelli, John P. Albers, William P. Irwin, Milton C. Blake, Jr., and Carl M. Wentworth

Thumbnail of and link to report PDF (11.9 MB)Summary

The Redding 1° x 2° quadrangle in northwestern California transects the Franciscan Complex and southern Klamath Mountains province as well as parts of the Great Valley Complex, northern Great Valley, and southernmost Cascades volcanic province. The tectonostratigraphic terranes of the Klamath province represent slices of oceanic crust, island arcs, and overlying sediment that range largely from Paleozoic to Jurassic in age. The Eastern Klamath terrane forms the nucleus to which the other terranes were added westward, primarily during Jurassic time, and that package was probably accreted to North America during earliest Cretaceous time. The younger Franciscan Complex consists of a sequence of westward younging tectonostratigraphic terranes of late Jurassic to Miocene age that were accreted to North America from mid-Cretaceous through Miocene time, with the easternmost being the most strongly metamorphosed. The marine Great Valley sequence, of late Jurassic and Cretaceous age, was deposited unconformably across the southernmost Klamath rocks, but in turn was underthrust at its western margin by Eastern belt Franciscan rocks. Pliocene and Quaternary volcanic rocks and sediment of the Cascades province extend into the southeastern part of the quadrangle, abutting the northernmost part of the great central valley of California.

This map and database represent a digital rendition of Open-File Report 87–257, 1987, by L.A. Fraticelli, J.P. Albers, W.P. Irwin, and M.C. Blake, Jr., with various improvements and additions.

Last modified November 13, 2012
First posted November 7, 2012

         Files for viewing and printing:

  • Pamphlet PDF (19 pages, 496 kB)
  • Map PDF (34.9" x 38.8", 11.9 MB)

         GIS data:

  • Readme TXT (8 kB)
  • Metadata TXT FGDC-compliant metadata documenting the vector geologic database (70 kB)
  • Arc export files ZIP Exported ArcInfo coverage, equivalent shape files, and accompanying metadata file (5.2 MB file that opens to a 16.5 MB folder)
  • Base image ZIP Base image and text description (4.0 MB file that opens to a 11.3 MB folder)
  • Original map image ZIP Image of the original, black-and-white geologic map (22.2 MB file that opens to a 27.7 MB folder)
  • This report is available only on the Web.

For additional information:
Contact Information, Earthquake Science Center, Menlo Park Science Center
U.S. Geological Survey
345 Middlefield Road, MS 977
Menlo Park, California 94025

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Suggested citation:

Fraticelli, L.A., Albers, J.P., Irwin, W.P., Blake, M.C., Jr., and Wentworth, C.M., 2012, Digital geologic map of the Redding 1° x 2° quadrangle, Shasta, Tehama, Humboldt, and Trinity Counties, California: U.S. Geological Survey Open-File Report 2012–1228, scale 1:250,000. (Available at

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