Spurs of the Peninsular Range of Southern California
extend southeasterly into the Salton Sink at several places along its western margin, and thus produce a mountain front characterized by deep re-entrant valleys. The origin of these
peculiar features has been much discussed, and with this
problem in view the present investigation was undertaken.
A strip about 15 miles wide across the southern portion
of the Indio Quadrangle, extending from the Salton Sea
westerly to the upland area of the main Peninsular Range
has been studied in some detail. Special attention has been
given to the structure.
This area includes two spurs, the Santa Rosa and
Coyote spurs, and two re-entrant valleys, Clark and Borego
Valleys
