STRUCTURAL GEOLOGY OF THE CENTRAL COYOTE MOUNTAINS, IMPERIAL COUNTY, CALIFORNIA

The Coyote Mountains of Imperial County in southeastern California show faulting associated with transpression along the Elsinore fault of the southern San Andreas fault system. Oblique stress over the past 1-2 million years has resulted in uplift of the range and exposed the Imperial and Split Mountain Formations from Miocene to Pliocene detachment faulting and marine incursion of the Gulf of California. The basin volcanics, conglomerates, sandstones, and mudstones are deposited as a nonconformity on the crystalline and metamorphic basement of the Peninsular Range batholith.

Strain partitioning has resulted in three major fault orientations proximal to the dextral Elsinore fault. A large, southwest dipping thrust fault parallel to the Elsinore results in principle uplift of the range. Adjacent normal faulting strikes perpendicular to shortening and has high-angle dips in both northwest and southeast orientations. Smaller east-northeast trending oblique faults are found between the Elsinore strike-slip displacement and basement thrust faulting. Present-day stresses along the Elsinore fault system may continue to drive the transpressional faults that shape the topography of the Coyote Mountains.