Geotimes, May 1992, v. 37, n. 5, pp. 16-19.

Tom Dibblee Jr. has been called "one of the most prolific geologic mappers of our time." It's not hard to understand why. Dibblee has mapped roughly 40,000 square miles of California, better than one-quarter of the state. That's more than anyone else before or since. Now more than 80 years old, Dibblee hasn't stopped. What follows is part of his story.

Born in 1911, Tom Dibblee grew up on Rancho San Julian, northwest of Santa Barbara, Calif. His father, Thomas Wilson Dibblee Sr., attended the University of California at Berkeley and took a course in geology from Joseph LeConte, the first professor of geology at the University of California. Tom Jr. was the oldest of four children and his first geologic experience came early.

In 1929, during the heyday of oil exploration around Santa Barbara, Dibblee's father brought in Harry R. Johnson, a consulting geologist and Stanford alumnus, to check the ranch's oil potential. Young Tom went with Johnson in the field and quickly developed an interest in fossil collecting and mapping. While still a high-school student, and without any formal training in geology, Dibblee mapped the area around the ranch in the western Santa Ynez Mountains. In 1932, Dibblee's father and Joseph Hollister (co-owner of the adjacent ranch and co-author, with R.D. Reed, of the 1936 book "Structural Evolution of Southern California") recommended Stanford as the best school for basic training in geology.

At Stanford Dibblee worked under Julian Barksdale, Paul F. Kerr, C.F. Tolman, Siemond W. Muller, and Aaron Waters. AS classmate Ben Page recalled, Tom Dibblee "reveled in the geology and soon established his legendary reputation for roaming harsh country with the greatest of ease on his own two feet. Moreover, he understood most of what he saw."

Dibblee graduated from Stanford in 1936 and went to work for the California Division of Mines in San Francisco, inventorying mercury deposits. Olaf P. Jenkins, state geologist and a Stanford alumnus, saw his geologic map of the western Santa Ynez Mountains, an area that had never been mapped before. This work eventually became California Division of Mines Bulletin 150, "Geology of Southwestern Santa Barbara County," published in 11950. That was the first of several bulletins published between 1952 and `1968. Dibblee mapped them all on his own time.

Late in 1936, Harold Hoots, chief geologist for Union Oil Co. and a Stanford alumnus, hired Dibblee to map the Lompoc Santa Ynez area and to determine its oil potential. Hoots was soon hired by Richfield Oil Corp., in Los Angles, and took Dibblee, Mason Hill and Manly Natland with him. Dibblee spent the next 15 years mapping geology of potential petroleum areas including the Temblor and Caliente ranges; Carrizo Plain; Cuyama; Salinas and Imperial Valleys; Santa Cruz Mountains; Eel River area; and parts of coastal Oregon and Washington.

Field work in those places and times as not easy. Dibblee later remarked, "Many of these areas were so remote that I camped out each night wherever I was at the end of the day. I had enough food and water for five days of field work every week. I slept each night in the car on the seat with one door open and a board extending outward on which to rest my legs. This gave enough shelter against cold winds, which blew fiercely at times. In this way I was able to get over much ground each week with little expense to the company. One month in Imperial Valley my expense account was $14.92. Hoots did not see how I could live on that amount, so on a visit he and exploration manager Frank Morgan treated me to a five-pound steak in Mexicali.

Richfield found oil in the Cuyama Valley in 1947. Mason Hill, one of Dibblee's coworkers at time, remembered that people said there "....was no oil west of the San Andreas fault in that area...and we decided to map (there). The first time we went out...Tom Dibblee and I took sleeping bags (there was just nothing out there then) and slept out by the side of the road. We spent a couple of days looking around. The roads weren't so good. We did a little reconnaissance work and then Tom Dibblee did some semi-detailed geologic mapping of quite a big area."

From their work, a favorable structure was found and an exploration well was drilled. At 3,100 feet, a 300-foot oil-bearing sand was discovered in the Vaqueros Formation. The formation yielded 5,000 barrels of oil a day in 1948. Richfield named this main producing unit the Dibblee sand.

Hill and Dibblee's years of geological collaboration at Richfield culminated in a paper, "San Andreas, Garlock and Big Pine Faults, California. A Study of the Character, History and Tectonic Significance of Their Displacement." The paper, done in the days before the plate tectonics theory was accepted, proposed a displacement along the San Andreas fault of more than 350 miles. This paper is now considered key to the foundation of the plate tectonics theory.

By 1952, Mason Hill said, Dibblee had "mapped all the sedimentary basins in California...all the potential oil-bearing sands." That year Dibblee accepted a position with the U.S. Geological Survey under D. Foster Hewett to map the geology of the California Desert. Because boron was a major ingredient in solid rocket fuel, one purpose of the study was to determine borate potential in the area. Dibblee mapped the western Mojave, producing numerous quadrangles and USGS Professional Paper 522, "Geology of the Western Mojave Desert." His work also extended southeastward into the south-central Mojave.

Dibblee's work with the Survey included a stint for the national Earthquake Research Branch, where he mapped the geology of the Transverse and coast Ranges in a swath 25 miles on each side of the San Andreas fault "from near the Mexican border to the San Francisco Bay." The result was nearly 100 open-file geologic quadrangles.

Dibblee's mapping techniques are legendary. he doesn't use a hammer to chip at rocks--he knows what all the rocks look like. And he seldom uses a hand lens or a compass. he used the topography and a natural feeling for what, the dips are.

"He has an innate, accurate and intuitive sense for mapping contacts and strikes and dips from observing the topography from vantage points," Tor Nilsen, one of Dibblee's colleagues remembers. "His prodigious memory and vast knowledge of stratigraphy and structure, rocks and fossils, enable him to rapidly sketch and place all necessary information directly onto his field sheets. His complete recall of details is reliable, even decades after working on a map>"

Tom Dibblee retired from the USGS in 1978, but his work hasn't stopped. He is a research associate with the University of California, Santa Barbara, and a consultant and volunteer for various government and civic agencies. At the request of the U.S. Forest Service in 1978 he began mapping the geology of the 1.2 million acre Los Padres National Forest of central coastal California on a voluntary basis to determine oil and gas potential, mineral resources, ground-water potential, potential fault hazards, landslides, unstable rock formations, and other geologic features. His efforts resulted in more than 100 geologic quadrangles.

Even today, Tom Dibblee is devoted to geology. In 1981 he explained, "The geologic mapping during my lifetime has been a sustained routine effort, driven by scientific curiosity. I did nothing glamerous, such as become a great executive, administrator, or teacher, or develop a revolutionary geologic theory. However, the geologic mapping I did in the Cuyama area led to the discovery of a major oil field there in 1948, and a little article I co-authored with Mason Hill on the San Andreas fault published in 1953, stimulated much interest in California geology, particularly on horizontal-slip fault tectonics. Since those years, I have been trying to provide as much basic field data on California geology as I can to the geologic community."

Dibblee's geologic maps provide an unsurpassed regional perspective, while at the same time contributing a wealth of locally important information. And his regional knowledge of the stratigraphy, structure, and paleontology has been basic to understanding much of the geology of California.

"I find it most important to record all my geologic observations onto a base map whenever I go out into the field, especially in areas of difficult access that I may never be able to return to. To me, this is the most logical field procedure, to record only basic geologic data, I an unbiased way, and with a minimum of interpretive inferences, Dibblee said recently. My mapping is not based on or influenced by theories or models; I prefer to let other geologists express their interpretations or ideas in whatever ways they wish rather than to include these on my maps.

Even before he retired, Dibblee was recognized for his efforts. In 1967, the Department of the Interior gave him its Distinguished Service Award. Stewart Udall, who as Secretary of the Interior at the time, praised Dibblee's highly accurate geologic maps, technological papers in some of the nation's leading scientific journals, and a wide spectrum of contributions in the publications series of the state of California and the Geological Survey. "For his later volunteer work in mapping for the Forest Service, Tom received the Presidential Volunteer Action Award in 1984 from President Reagan. His other awards include Honorary Membership in the Pacific Section of the American Association of Petroleum Geologists, the Society of Economic Paleontologists and Mineralogists, and the South Coast Geological Society: the Human Needs Award fro the American Association of Petroleum Geologists; and the Bronze Medal of the University of California.

Dibblee still lives in Santa Barbara with his wife, Loretta, and occasionally spends time at Rancho San Julian, one of the few remaining California ranches owned by the descendants of its grantee. Last year he celebrated his 80th birthday under the grape arbor of La Casa Grande on Rancho San Julian along with 80 relatives and friends. He remains active in field work at least one day a week, and he has published more than 45 geologic quadrangles in the last five years. More are currently in press. He continues to contribute articles, abstracts, and poster sessions, lead field trips, and give presentations to the geologic community.

Tom Dibblee's recent work has involved a variety of topics including the tectonic significance of Mid-Tertiary conglomerates of Southern California, the geology of the Oak Ridge uplift in Ventura County, displacement of rock terrranes by the San Andreas fault, and geology of the Santa Monica Mountains and Simi Hills. He is currently working on the late Cenozoic tectonics of several faults in the Mojave Desert and on the geology of oil basins in coastal northern California.

In 1983 a group of Tom Dibblee's colleagues realized that his many unpublished geologic maps should be preserved for their scientific and educational value and that as many as possible should be made publicly available. They formed the Thomas Wilson Dibblee Jr. Geological Foundation, a non-profit corporation that honors Dibblee's many contributions to the earth sciences by seeking and providing funds to print his many unpublished geologic maps of California.

So far the Foundation has published 42 maps encompassing 56 quadrangles. Many more are due to be published. The maps have a uniform scale and color code--darkest colors are generally oldest rock formation, the lightest, the most recent--and sell for $10 each <editors note: $12  for 1997>. Users include engineering geologists, oil companies, planning agencies, researchers and educators, environmental consultants, archaeologists, and realtors and developers. Because the greatest demand is for maps of coastal and urban areas, the focus is on publishing these, ranging from central California to the Los Angeles Basin.

Geologist Helmut Ehrenspeck manages the day-to-day operations of the Dibblee Geological Foundation. Ehrenspeck has devoted the last several years to mapping with Dibblee and is responsible for taking his field maps through all phases of preparing maps for full-color publication. Because the Dibblee Foundation is a small, non-profit organization with very limited personnel and financial resources, but with an ambitious publication program, it needs an inexpensive, technically simple alternative process to standard mapmaking procedures. Enrenspeck devised a full-color printing technique, based on methods used in the cartooning and film industry, that is faster and much less expensive than conventional cartographic printing methods.

For more information about the Dibblee Geological Foundation and its mapping program, or to consider contributing, write to the Dibblee Geological Foundation, Box 60560, Santa Barbara, Calif. 93160.

Dorothy L. Stout

Physical Sciences Department

Cypress College

9200 Valley View St.

Cypress CA  90630

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