Oil Exploration in the Western San Joaquin Valley
Rare, separately-published example of an important geological map of the Coast Ranges between Livermore and Coalinga, compiled by Robert Anderson and R. W. Pack.
The map shows the western part of the San Joaquin Valley in two parts. They show this sparsely-populated and dry part of California in magnificent detail, with a high geological resolution. A legend in the lower left names the various formations of the region and gives their approximate ages. Geological symbols are also shown.
The study that produced this map was notable for a number of reasons. It established the Cretaceous age of the oil-bearing shale of the Coalinga and Vallecitos districts. It also established the existence of the anticlines and synclines that allowed for the accumulation of oil in those two districts.
This map was published during the apex of California oil expansion, at a time when new fields were being developed all over and the Coalinga and Livermore fields were all-important. Many in the oil industry started to wonder if the Coast Ranges between those two fields would also contain oil. To this effect, Anderson and Pack mentioned in a report that some of the areas shown on the map "had been withdrawn by the President of the "United States on the recommendation of the Department of the Interior as possible oil lands pending investigation" and public entry was limited.
Pack and Anderson failed to find any strong evidence of possible large oil reserves in this area. However, their careful geological study represented an early example of methodological application of scientific technique to the study of oil discovery. This is summarized on the present map.