Structural geology of the Central Coyote Mountains Imperial County, California

The Coyote Mountains are a small mountain range in a tectonically complex region of southern California. Previously undisturbed units of the Salton Trough have been uplifted, faulted, and deformed from displacement on the oblique Elsinore Fault of the southern California San Andreas fault system. Uplift and erosion have exposed the metamorphic basement complex and older Tertiary stratigraphic sequence for geologic interpretation. Sedimentary and volcanic units were originally deposited on a highly irregular basement topography prior to faulting and deformation. Three east-west trending infilled paleocanyons are exposed within the mountain range and preserve the oldest Tertiary stratigraphy from erosion. Younger sedimentary units were preserved by fault escarpments in the basement complex. Transpressional stresses from the Elsinore Fault resulted in strain partitioning and the creation of a synthetic and antithetic fault array observed in the system. Two large oblique synthetic faults strike to the northwestsoutheast and create elongate structures in the typically unfaulted basement complex. Several smaller antithetic faults strike to the northeast-southwest and typically possess sinistral and normal displacement opposite the major Elsinore Fault. Antithetical faults in the basin to the north of the range have hinged motion from torsional stresses in the system. Most of the measurable bedding orientations in the stratigraphic sequence have been translocated with the basement complex to their current orientations. Older sedimentary and volcanic units have been tilted with the large sections of uplifted basement complex during transpressional mountain formation. Younger, less indurated sedimentary units show ductile deformation to the south of the range. Folding in the younger sedimentary stratigraphy may be indicative of system-wide folding early in the geologic history of the Coyote Mountains. The youngest stratigraphic units are high elevation older alluvium deposited after the onset of uplift and the erosion of the original basin stratigraphy. Found on the range crests and mountain flanks, the older Quaternary conglomerates are derived from the ancestral Coyote Mountains and are deposited as an angular unconformity with the faulted older stratigraphy. The unconsolidated units were uplifted to their current elevations from continued displacement on the Elsinore Fault.