page_title: Coyote Mountains
section_title: Influence of the Colorado River Delta
hierarchical_section_title: Coyote Mountains / Geology / Influence of the Colorado River Delta
caption_attribution_description: English: Erosion in Anza-Borrego
context_page_description: The Coyote Mountains are a small mountain range in San Diego and Imperial Counties in southern California. The Coyotes form a narrow ESE trending 2 mi wide range with a length of about 12 mi. The southeast end turns and forms a 2 mi north trending "hook". The highest point is Carrizo Mountain on the northeast end with an elevation of 2,408 feet. Mine Peak at the northwest end of the range has an elevation of 1,850 ft. Coyote Wash along I-8 along the southeast margin of the range is 100 to 300 feet in elevation. Plaster City lies in the Yuha Desert about 5.5 mi east of the east end of the range.
  To the southeast lie the Jacumba Mountains and the Volcanic Hills. To the north and northeast lie the Carrizo Badlands, the Carrizo Valley and the Fish Creek Mountains. The west end of the range is within the Anza-Borrego Desert State Park and the east end is within the Carrizo Naval Gunnery Range. The international border lies approximately 11 mi south of the southeast margin of the range.
  The range consists of sand dunes left over from the ancient inland Sea of Cortez. Seismic activity has raised these.
context_section_description: The marine incursion of the ancestral Gulf of California also introduced a single, very large depositional system (the Colorado River delta) into the Salton Trough, which rapidly prograded to the south (Winker and Kidwell, 1986). During the early Pliocene, between 5 and 4.2 million years ago, this deltaic system facilitated the deposition of a thick marine deltaic sequence of mudstone and sandstone derived from the Colorado River, known as the Deguyños Formation of the Imperial Group (formerly the Imperial Formation). The Deguyños Formation represents the distal prodelta portion of the Colorado River delta, and is characterized by upward-coarsening cycles of claystone, siltstone, sandstone and/or coquina shell beds.
  As the Colorado River depositional system evolved later in the Pliocene, between 4.2 and 2.8 million years ago, the marine deltaic phase gave way to a meandering fluvial system. Deposition of marine sedimentary deposits gradually transitioned into deposition of nonmarine, predominantly fluvial/delta front sediments of the Colorado river. In the Coyote Mountains, this is expressed by the presence of upward fining sequences of fine, light pink to pale orange sandstones and reddish-gray mudstones, known as the Arroyo Diablo Formation of the Palm Spring Group (previously the Diablo member of the Palm Spring Formation).
  Further deposition of locally derived sediments continued to accumulate in the area between 2.8 and ≈1 million years ago, primarily manifested by the Hueso Formation. Eventually (0.95 Ma), the tectonic regime in the area changed, and basin subsidence and accumulation of sediments ceased.
caption: Erosion of sediments in the Coyote Mountains
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