Imperial Valley

Abstract

Abstract The Imperial Valley area, as used in this paper, is the northwesterly extension of the long trough occupied by the Gulf of California. Topographically it is now separated from the Gulf of California by the recent delta of the Colorado River. Its divisions northwestward from the Colorado River delta are Imperial Valley, or Salton Sink, and Coachella Valley which culminates in San Gorgonio Pass. High mountains of granitic and metamorphic rocks capped by isolated erosional remnants of Cenozoic sediments form the northeast and southwest margins of the valley. Large talus and terrace deposits extend from the mountains and coalesce with the alluvium and lake beds which cover the central part of the valley. Cenozoic marine and continental sedimentary formations crop out at scattered places in the Imperial Valley area. These sediments were deposited in basins of deposition which may have extended over part of southeastern California and western Mexico during parts of Tertiary and Quaternary time. They are well exposed in the western part of Imperial Valley, as illustrated on the accompanying map, and in the Indio and Mecca hills which extend as a narrow discontinuous range of hills from the northern end of Salton Sea northwest throughout the length of Coachella Valley. The geology discussed in this paper is based on an unpublished study of the Cenozoic sediments exposed in the western part of Imperial Valley. The Imperial and Palm Spring are the only formational units used which have been described in previous publications. The basement complex in the