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125 Years of Science for America - 1879 to 2004
U.S. Geological Survey
Scientific Investigations Map 2858

Geology, Tephrochronology, Radiometric Ages, and Cross Sections of the Mark West Springs 7.5' Quadrangle, Sonoma and Napa Counties, California

By R.J. McLaughlin, A.M. Sarna-Wojcicki, R.J. Fleck, W.H. Wright, V.R.G. Levin, and Z.C. Valin

2004

thumbnail image of map

The purpose of this geologic map is to provide a context within which to interpret the Neogene evolution of the active strike-slip fault system traversing the Mark West Springs 7.5' quadrangle and adjacent areas. Based on this geologic framework, the timing and total amounts of displacement and the Neogene rates of slip for faults of the right-stepover area between the Healdsburg and Maacama Faults are addressed.

The Mark West Springs quadrangle is located in the northern California Coast Ranges north of San Francisco Bay. It is underlain by Mesozoic rocks of the Franciscan Complex, the Coast Range ophiolite, and the Great Valley sequence, considered here to be the pre-Tertiary basement of the northern Coast Ranges. These rocks are overlain by a complexly interstratified and mildly to moderately deformed sequence of Pleistocene to late Miocene marine and nonmarine sedimentary and largely subaerial volcanic rocks. These rocks and unconformably overlying, less-deformed Holocene and Pleistocene strata are cut by the active right-lateral Healdsburg and Maacama Fault Zones.

Mapping of the Mark West Springs quadrangle began in 1996 and was completed in October 2002. Most of the mapping presented here is original, although a few other sources of existing geologic mapping were also utilized. Funding for the project was provided by the National Cooperative Geologic Mapping and Earthquake Hazards Reduction programs of the U.S. Geological Survey, in cooperation with geologic hazards mapping investigations of the California Geological Survey.

 

 

File Name
File Type and Description
File Size
FILES for VIEWING and PLOTTING
SIM2858-pamphlet.pdf
PDF file of the 16-page Geology pamphlet containing description of map
96 KB
SIM2858-sheet1.pdf
PDF file of 48" x 36" map sheet 1 that can be used for viewing map in a browser, as well as for plotting (geologic map, description of map units, and correlation of map units)
17.9 MB
SIM2858-sheet2.pdf
PDF file of 48" x 36" map sheet 2 that can be used for viewing map in a browser, as well as for plotting (cross sections, chemistry, geochronology, and structure)
3 MB
SIM2858-sheet1.jpg
JPG file of 11" x 17" 300 dpi version of the map sheet 1 that can be used for viewing map in a browser or printing on tabloid-sized paper
5.1 MB
SIM2858-sheet2.jpg
JPG file of 11" x 17" 300 dpi version of the map sheet 2 that can be used for viewing map in a browser or printing on tabloid-sized paper
1.8 MB
README
SIM2858-readme.txt
ASCII text file that gives the description of the digital files
140 KB
DATA
SIM2858.tar.gz
Compressed file that contains geodatabase data objects
624-KB file that opens into a 3.1-MB folder called mws
SIM2858-met.txt
ASCII text file of the metadata that gives detailed information about the data
140 KB

Version history

For questions about the content of this report, contact Bob McLaughlin


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URL of this page: http://pubs.usgs.gov/sim/2004/2858/
Maintained by: Michael Diggles
Date created: November 28, 2004
Date last modified: July 2, 2007 (mfd)