Marine Oligocene of the West Coast of North America

Abstract

Introductory Remarks This paper comprises a general survey of the known data concerning the paleogeography, climatic conditions, and faunal relationships of the Oligocene as found in California, Oregon, Washington, and Vancouver Island. The great thickness of the marine Tertiary sediments on the West Coast forms a striking contrast to the much thinner deposits of the same age found in the Gulf and Atlantic Coastal Plain province ; also the evidences of crustal movements of enormous magnitude, which are represented by great angular unconformities at various horizons in the Tertiary of the West Coast, indicate conditions very different from those which existed during the same general period in the eastern region. The Tertiary deposits on the West Coast were, for the most part, laid down in geosynclinal depressions which paralleled the axes of the present mountain ranges. In these slowly sinking troughs the sediments sometimes accumulated to enormous thickness before deposition was interrupted, . . .