Structural geology of the central Coyote Mountains, Imperial County, California

The Coyote Mountains are a small mountain range in a tectonically complex \nregion of southern California. Previously undisturbed units of the Salton Trough have \nbeen uplifted, faulted, and deformed from displacement on the oblique Elsinore Fault of \nthe southern California San Andreas fault system. Uplift and erosion have exposed the \nmetamorphic basement complex and older Tertiary stratigraphic sequence for geologic \ninterpretation. \nSedimentary and volcanic units were originally deposited on a highly irregular \nbasement topography prior to faulting and deformation. Three east-west trending infilled \npaleocanyons are exposed within the mountain range and preserve the oldest Tertiary \nstratigraphy from erosion. Younger sedimentary units were preserved by fault \nescarpments in the basement complex. Transpressional stresses from the Elsinore Fault \nresulted 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 \nand create elongate structures in the typically unfaulted basement complex. \nSeveral smaller antithetic faults strike to the northeast-southwest and typically possess \nsinistral and normal displacement opposite the major Elsinore Fault. Antithetical faults in \nthe basin to the north of the range have hinged motion from torsional stresses in the \nsystem. \nMost of the measurable bedding orientations in the stratigraphic sequence \nhave been translocated with the basement complex to their current orientations. Older \nsedimentary and volcanic units have been tilted with the large sections of uplifted \nbasement complex during transpressional mountain formation. Younger, less indurated \nsedimentary units show ductile deformation to the south of the range. Folding in the \nyounger sedimentary stratigraphy may be indicative of system-wide folding early in the \ngeologic history of the Coyote Mountains. \nThe youngest stratigraphic units are high elevation older alluvium deposited \nafter the onset of uplift and the erosion of the original basin stratigraphy. Found on the \nrange crests and mountain flanks, the older Quaternary conglomerates are derived from \nthe ancestral Coyote Mountains and are deposited as an angular unconformity with the \nfaulted older stratigraphy. The unconsolidated units were uplifted to their current \nelevations from continued displacement on the Elsinore Fault.