Geologic Map and Map Database of Eastern Sonoma and Western Napa Counties, California

Scientific Investigations Map 2956
By: , and 



Introduction This report contains a new 1:100,000-scale geologic map, derived from a set of geologic map databases (Arc-Info coverages) containing information at 1:62,500-scale resolution, and a new description of the geologic map units and structural relations in the map area. Prepared as part of the San Francisco Bay Region Mapping Project, the study area includes the north-central part of the San Francisco Bay region, and forms the final piece of the effort to generate new, digital geologic maps and map databases for an area which includes Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz, Solano, and Sonoma Counties. Geologic mapping in Lake County in the north-central part of the map extent was not within the scope of the Project. The map and map database integrates both previously published reports and new geologic mapping and field checking by the authors (see Sources of Data index map on the map sheet or the Arc-Info coverage eswn-so and the textfile eswn-so.txt). This report contains new ideas about the geologic structures in the map area, including the active San Andreas Fault system, as well as the geologic units and their relations. Together, the map (or map database) and the unit descriptions in this report describe the composition, distribution, and orientation of geologic materials and structures within the study area at regional scale. Regional geologic information is important for analysis of earthquake shaking, liquifaction susceptibility, landslide susceptibility, engineering materials properties, mineral resources and hazards, as well as groundwater resources and hazards. These data also assist in answering questions about the geologic history and development of the California Coast Ranges.

Study Area

Publication type Report
Publication Subtype USGS Numbered Series
Title Geologic Map and Map Database of Eastern Sonoma and Western Napa Counties, California
Series title Scientific Investigations Map
Series number 2956
DOI 10.3133/sim2956
Edition Version 1.0
Year Published 2007
Language ENGLISH
Publisher Geological Survey (U.S.)
Contributing office(s) Western Earth Surface Processes
Description Map (35 x 50 inches); Pamphlet (ii, 28 p.); Read Me; Data Files
Scale 1
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details