Preliminary Geologic Maps

Above: Index map showing available quadrangles of the modern California Regional Geologic Map series. Smallest squares represent 7.5 minute quadrangles (1:24,000 scale). Larger rectangles represent 30-by-60 minute quadrangles (1:100,000 scale). Click or tap the image to open a larger version.
Preliminary Geologic Maps (PGM) are available only as PDF files, using the links provided below. Printed versions are not available.

Geologic map preparation at the CGS generally follows a three-step process. First, we complete selected 7.5-minute quadrangles at 1:24,000 scale. Then we compile this mapping into 30-by-60-minute quadrangles at 1:100,000 scale; the 7.5-minute and initial 30-by-60-minute quadrangles are published on this page as Preliminary Geologic Maps. Following a period of review, 30-by-60-minute quadrangles are elevated into the Regional Geologic Map series as the third step in the process, with the long-term goal of creating a seamless digital geologic map of the state at a scale of 1:100,000.

The California Geological Survey prepares geologic maps in cooperation with the U.S. Geological Survey's National Cooperative Geologic Mapping Program. Geologic mapping priorities are established by the California State Geologist and the California Geologic Mapping Advisory Committee.

For data requests and technical comments related to Geologic Mapping, please contact Brian Swanson.

Preliminary 30-by-60 Minute Quadrangles (1:100,000 scale)

Preliminary 7.5 Minute Quadrangles (1:24,000 scale)

Select a region from the choices below to jump to a list of that region's 7.5 minute quadrangles.

Ukiah Region Healdsburg-Napa Region Truckee Region San Andreas Region San Luis Obispo Region Lancaster-Victorville Region Santa Barbara-Los Angeles Region Big Bear Lake Region Oceanside-San Diego Region New York Mtns-Ivanpah Region Imperial County-Yuma Region

Ukiah Region

Map of the Ukiah Region showing available quadrangles.

Healdsburg-Napa Region

Note: The 7.5 minute quadrangles within the Napa 30-by-60 minute quadrangle (outlined in red below) have been updated and are superseded by the Preliminary Geologic Map of the Napa-Bodega Bay 30-by-60 minute quadrangle (Wagner and Gutierrez, 2017).
Map of the Healdsburg-Napa Region showing available quadrangles.

Truckee Region

Map of the Truckee Region showing available quadrangles.

San Andreas Region

Map of the San Andreas Region showing available quadrangles.

San Luis Obispo Region

Note: The 7.5 minute quadrangles shown below have been updated and are superseded by the Preliminary Geologic Map of the West Half of the San Luis Obispo 30-by-60 minute quadrangle (Wiegers, 2018; un-simplified digital database available upon request).
Map of the San Luis Obispo Region showing available quadrangles.

Lancaster-Victorville Region

Map of the Lancaster-Victorville Region showing available quadrangles.

Santa Barbara-Los Angeles Region

Note: The 7.5 minute quadrangles within the Los Angeles 30-by-60 minute quadrangle (outlined in red below) have been updated and are superseded by the Preliminary Geologic Map of the Los Angeles 30-by-60 minute quadrangle (Campbell, et al, 2014).
Map of the Santa Barbara-Los Angeles Region showing available quadrangles.

Big Bear Lake Region

Map of the Big Bear Lake Region showing available quadrangles.

Oceanside-San Diego Region

Note: The 7.5 minute quadrangles within the Oceanside 30-by-60 minute quadrangle (outlined in red below) have been updated and are superseded by the Geologic Map of the Oceanside 30-by-60 minute quadrangle (Kennedy and Tan, 2007).
Map of the Oceanside-San Diego Region showing available quadrangles.

New York Mountains-Ivanpah Region

Map of the Ivanpah Region showing available quadrangles.

Imperial County-Yuma Region

Map of the Imperial County-Yuma Region showing available quadrangles.

Web page by:
California Geological Survey - Regional Geologic and Landslide Mapping Program

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