Abstract

The Temblor Range at the southwestern margin of the San Joaquin Valley is underlain by a diverse suite of Upper Cretaceous to Recent strata that record a complex succession of paleogeographic and paleotectonic events. A series of large, generally anticlinal oil fields, including the Midway-Sunset Oil Field, lie along the northeastern margin or northeast of the range. Because production in these fields is largely from clastic reservoirs that crop out to varying extents in the range, the geology of the Temblor Range has been the subject of a great number of previous published and unpublished studies that include field mapping, structure, stratigraphy, paleontology, sedimentology, and related disciplines.

The new geologic map released in conjunction with this field trip guidebook as Plate 1 covers the portion of the range marginal to the northern Midway-Sunset Oil Field and covers only post-lower Miocene strata. These units include the Miocene Monterey Formation, the Pliocene and Pleistocene Tulare Formation, and diverse Quaternary nonmarine deposits. The Monterey Formation includes a succession of diatomaceous shales, altered diagenetically to varying mineralogies, and a number of sandstone bodies that appear to have been deposited as submarine canyons and submarine fans. The Tulare Formation rests with angular unconformity on the Monterey Formation and consists in outcrop of alluvial-fan deposits derived from erosion of the Temblor Range. A large number of generally northwest-trending folds are present in the mapped area and a few minor faults.