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First Edition of Jenkins's Monumental Geological Map of California.

A fine example of Olaf Jenkin's mammoth geological map of California, published by the state Division of Mines in 1938.

This one-inch-to-eight-mile geologic map shows the region's strata as they were then understood. Some approximately fifty different types of units are shown, ranging in geological age and type of formation. The major structures are easily identifiable, including the melange of the central coast, the massive batholiths of the sierras, the small, varied ranges of the desert regions, and the giant San Andreas fault. 

The regions still unmapped range from the high Sierras to the remote northern coast and even regions just inland of San Diego.

Many inset maps appear throughout, showing average annual precipitation, the sources of the data, the township and range system, former glaciation in the Sierras, and a geomorphic map of the state. 

Olaf Pitt Jenkins

Olaf Jenkins was born and raised in the trans-disciplinary academic environment of San Francisco that predominated at the start of the 20th century. His father was a physiologist at Stanford, and he was raised near the campus and mentored from a young age by some of the foremost natural scientists of the day.

Jenkins initially worked on government fisheries and studied the golden trout in the Sierra Nevada. However, he then pivoted to geology, working on Stanford expeditions to the Coast Range and Brazil, before mapping eastern parts of the US. He pivoted to economic geology and worked with Standard Oil for a period when the benefits of geology to resource production were just starting to become apparent. In this capacity, he worked in Indonesia

He then pivoted back to academia, earning his doctorate and behind hired as the chief geologist at the newly created Geologic Branch of the Division of Mines. His first project was this monumental geologic map, which he invited a number of researchers to work on.

He produced a number of other important works during his time in the position, including bibliographies on California's oil fields. He remains one of the most well-recognized Californian geologists.

Rarity

While the map is not institutionally rare, we locate only a single other that has been offered for sale.