Dibblee’s California maps available

Mapping Talents, Passion Created a Legend

Famed geologist Tom Dibblee’s legacy continues with the Dibblee Geologic Map Collection.
Famed geologist Tom Dibblee���s legacy continues with the Dibblee Geologic Map Collection.

While attending Stanford University in 1932 Tom Dibblee may not have known he would become a legend and the most famous field geologist in California (or have a Wikipedia page!), but he did know he wanted to be a field geologist like those at the U.S. Geological Survey.

When he was in high school, Tom followed consulting geologist Harry R. Johnson around his family’s 20,000-acre ranch while Johnson accessed the ranch for its oil potential. By the end of that summer Tom had produced a geologic map of his own that, in retrospect, looked remarkably similar to the geologic map of that portion of the Tajiguas Quadrangle his non-profit (the Dibblee Geological Foundation) published in 1988.

Later, when still in high school on trips accompanying his father east into the Central Valley of California, Tom started identifying similar stratigraphic sections to those he had seen on his ranch.

His 70-plus-year-long mapping career had begun.

Upon graduation from Stanford in 1936, Tom went to work for Union Oil and then on to Richfield where his field mapping led to the discovery of the Russell Ranch field in near New Cuyama. By 1952 Tom had mapped all the oil-potential sedimentary basins in California, and his legendary reputation for roaming the back country on foot for weeks at a time became part of his lore.

From Richfield, Tom went on to fulfill his dream of becoming a field geologist for the USGS.

With the USGS he mapped the Western Mojave Desert, evaluating known and potential borate deposits for boron in making rocket fuel. Following that assignment he mapped 25 miles each side of the San Andreas Fault, from the Coachella Valley to north of the San Francisco Bay. That project alone resulted in more than 100 published quadrangles.

After retiring in 1977 Tom began mapping the geology of the 1.2-million-acre Los Padres National Forest of central coastal California on a voluntary basis. His efforts in the Los Padres Forest resulted in more than another 100 geologic quadrangles and a Presidential Volunteer Action Award from President Reagan in 1983.

In all, Tom mapped more than 550 quadrangles at scales of 1:24,000 and 1:62,500 that form a nearly continuous mosaic of regional field geology east of the Sierras from north of San Francisco to near the Mexican Border – about one quarter of the state of California.

Finding a Home

One of the beauties of the Dibblee Geologic Map Collection is how remarkably consistent the nomenclature and color schemes are throughout the series. Great care was taken by Tom and his editors to ensure this consistency.

Tom had a very special ability to remember what rocks he had seen and where, and their association with other units. He also could rapidly and rather accurately determine the orientation of the bedding and structure from a distance, allowing the opportunity to move through an area quickly.

His knowledge of regional stratigraphy, structure and paleontology has been basic to understanding much of California’s geology (Dorothy L. Stout, GeoTimes, May 1992).

In the early 1980s a group of Tom’s colleagues formed the Thomas Wilson Dibblee Jr. Geological Foundation. The Foundation’s mission was simply to help preserve the scientific, technical, educational and economic values of Dibblee’s life work through timely publication of hundreds of maps.

In June 2002 the Dibblee Geological Foundation’s mission was adopted by the Santa Barbara Natural History Museum, and in response created the Dibblee Geology Center. That mission of timely publication was fulfilled in 2008 with the completion of 419 geologic maps of more than 550 quadrangles; first under editor Helmut E. Ehrenspeck, who passed away in 2001, and then by editor and AAPG member John A. Minch, who completed the project.

Dibblee worked every day on his maps to within a couple weeks of his passing away – he would have been 100 years old last October – and he not only mapped while at work but spent most of his free time throughout his life mapping in areas that were located between his assignments.

In the late 1980s the Dibblee Geological Foundation Board postulated that map sales of the Santa Monica Mountain quadrangles would generate needed cash because of the heavy development-related consultant base in the Los Angeles area, and asked Tom to map them. He set out with his field partner Helmut Ehrenspeck and completed the dozen quadrangle assignment within a few years time.

Dibblee commented after that it was some of the most complicated geology he had ever mapped.

The Dibblee Map Collection

The Dibblee Geologic Map Collection of 419 maps is available in both paper and electronic formats. Paper versions of the Dibblee Maps can be purchased at the Santa Barbara Museum of Natural History store and electronic Geo-PDFs are available through the AAPG Datapages. Volume deals resulting in as much as 25 percent off are available on paper maps through the regional specials at the Santa Barbara Natural History Museum store. Volume deals also are available on electronic versions in three regional sets, including the Northern Basin, Humboldt Basin and Desert through the Datapages.

The digital maps feature high quality PDFs created from the original files, and include a USGS topographic map overlay layer. Maps are geo-registered to the four corners of each map using the original USGS overlay projection:

  • North American Datum 1927 (NAD 27).
  • Universal Transverse Mercator Grid (UTM zone 10 or zone 11).

A wide format printer is required for full size printing.

Funding for publishing and later digitizing all of the Dibblee Geologic Map Collection was predominantly a grass-roots effort of private and corporate donors and foundation re-gifting, such as from the AAPG Foundation. No government funds were made available or utilized.

To complete the digitization of the initial 76 maps (for the Datapages Project), funding was borrowed from other sources.

We are asking for contributions to retire that debt. One way to contribute is to purchase a block of maps, requesting that the funds be applied to retiring the debt.

For more information contact John Minch.

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Digital Maps

All 419 maps in the Dibblee Map Collection are featured in AAPG’s online bookstore for immediate download. Each quadrangle is priced at $22.

By the time the Dibblee Geological Foundation completed the map collection, many users wanted the maps in digital formats as well as in print. The Foundation approached AAPG Datapages to help provide an e-commerce solution, and all maps were placed into the Digital Download program at the AAPG Bookstore (other maps are in press, but release dates are uncertain because so much remains to be done).

To date, all maps have been available as layered PDFs (see main story). Most maps are less than two mb (file size). In May AAPG Datapages received word all maps have been converted to a geo-referenced TIF format and also will be provided for customer download at the bookstore (also at a price of $22 per quadrangle).

The advantage of a geo-referenced TIF file is it can be immediately imported to a common GIS mapping application for use as a data layer in an E&P project. Although it is possible to extract an information layer from a layered PDF, the new geo-TIF maps will save the user several steps and guarantee higher mapping accuracy.

“We have not determined a release date of the geo-TIF maps,” says Ron Hart, of AAPG Datapages, “but it is a high priority project for us and we already are working on a solution to speed the release. Watch for announcements later this fall.”

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