The marine and continental sediments which occur in Imperial Valley may be divided into the following formations.

1. Split Mountain formation: Miocene (?) marine and continental sediments.

2. Alverson Canyon formation: Miocene (?) non-marine sediments and associated volcanic flows.

3. Imperial formation: Miocene marine sediments.

4. Palm Spring formation: Miocene and/or Pliocene marine and non-marine sediments.

5. Borrego formation: Lower Pleistocene (?) non-marine sediments.

Surface and well data indicate that at least 14,000 feet of sediments were present west of Salton Sea at the end of deposition of Borrego formation and as much as 25,000 feet of sediments may be present in the central part of Salton Sink.

Structurally Imperial Valley is a series of parallel fault blocks. The general trend of the major faults is N. 55° W. Two of these faults which are well known and extend beyond Imperial Valley are the San Jacinto and San Andreas. The sediments have two structural alignments, one sub-parallel with the major faults and the other trending east-west.

On the basis of surface data the possibility of obtaining commercial quantities of natural gas or crude oil appear to be very meager. Although a composite section of 22,000 feet of sediments is exposed at many places in the western part of Imperial Valley, only 3,600 feet are of definite marine origin. The writer has observed no indication of petroleum except for small quantities of methane gas, comparable to that in many present-day swamps, in the non-marine sediments of the Palm Spring and Borrego formations.

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