The Coyote Mountains are a small mountain range in

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United State ...

and Imperial Counties in southern

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

.''El Cajun, California,'' 30x60 Minute Topographic Quanrangle, USGS, 1979 The Coyotes form a narrow ESE trending wide range with a length of about . The southeast end turns and forms a north trending "hook". The highest point is Carrizo Mountain on the northeast end with an elevation of . Mine Peak at the northwest end of the range has an elevation of . 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 east of the east end of the range.''Carrizo Mountain, California,'' 15 Minute Topographic Quadrangle, USGS, 1959''Plaster City, California,'' 15 Minute Topographic Quadrangle, USGS, 1957 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 Fish Creek Mountains are a mountain range in Lander County, Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona ...

. The west end of the range is within the

Anza-Borrego Desert State Park Anza-Borrego Desert State Park (, '' AN-zə bə-RAY-goh'') is a California State Park located within the Colorado Desert of southern California, United States. The park takes its name from 18th century Spanish explorer Juan Bautista de Anza and ...

and the east end is within the Carrizo Naval Gunnery Range. The international border lies approximately 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. Much of the terrain is still loose dirt, interspersed with sandstone and occasional quartz veins. A dirt road leads towards the mountains, starting off State Highway 2 (S2), also known as the Imperial Highway, not far from the desert community of

Ocotillo ''Fouquieria splendens'' (commonly known as ocotillo (), but also referred to as buggywhip, coachwhip, candlewood, slimwood, desert coral, Jacob's staff, Jacob cactus, and vine cactus) is a plant indigenous to the Sonoran Desert and Chihuahuan ...

. There are no marked trails and the footing is treacherous, made up of loose sand, dirt and crumbled shards of sandstone. Most slopes have no vegetation, but there is occasional

mesquite Mesquite is a common name for several plants in the genus '' Prosopis'', which contains over 40 species of small leguminous trees. They are native to dry areas in the Americas. They have extremely long roots to seek water from very far under gr ...

and

ocotillo ''Fouquieria splendens'' (commonly known as ocotillo (), but also referred to as buggywhip, coachwhip, candlewood, slimwood, desert coral, Jacob's staff, Jacob cactus, and vine cactus) is a plant indigenous to the Sonoran Desert and Chihuahuan ...

, with coastal cholla at lower elevations. The local fauna includes jackrabbits and sparrows. There are a few ancient sand dunes that have been fossilized and hollowed out by winds, producing wind caves. Marine fossils such as sand dollars and snails can be found, but it is illegal to remove any fossils. In 1994, the

United States Congress The United States Congress is the legislature of the federal government of the United States. It is bicameral, composed of a lower body, the House of Representatives, and an upper body, the Senate. It meets in the U.S. Capitol in Washing ...

designated 18,631 acres (75 km²) as a U.S. Bureau of Land Management managed U.S. Wilderness Area, the Coyote Mountains Wilderness.

Geology

The Coyote Mountains range consists of

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metamorphic basement rocks overlain by younger

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...

and

sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

rocks. The peaks and mountain ranges are primarily

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

and

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

basement rocks, which consist of

marble Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated (layered), although there are exceptions. In geology, the term ''marble'' refers to metamorphose ...

schist Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...

, and

gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures a ...

. This metamorphic basement rock and overlying volcanic and sedimentary rocks have been uplifted and exposed due to

seismic activity An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...

along the

Elsinore Fault Zone The Elsinore Fault Zone is a large right-lateral strike-slip geological fault structure in Southern California. The fault is part of the trilateral split of the San Andreas fault system and is one of the largest, though quietest faults in Souther ...

Volcanism

During the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, around 22-14 million years ago, volcanic activity produced various volcanic rock features including

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

flows, an

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predo ...

plug, and various

volcaniclastic Volcaniclastics are geologic materials composed of broken fragments ( clasts) of volcanic rock. These encompass all clastic volcanic materials, regardless of what process fragmented the rock, how it was subsequently transported, what environment it ...

s including

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

s and

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...

s, known as the Alverson Formation. These volcanic rocks are primarily exposed along the east and southeastern portion of the range, and are best viewed and easily accessed in th
Painted Gorge
area of the range (where multiple volcanic rock types of varying colors are exhibited, giving the area a gorgeous 'painted' appearance).

Marine incursion

During the late Miocene, initiation of motion on the West Salton detachment fault caused rapid subsidence of the

Salton Trough The Salton Trough is an active tectonic pull-apart basin, or graben. It lies within the Imperial, Riverside, and San Diego counties of southeastern California, United States and extends south of the Mexico–United States border into the stat ...

region, resulting in a marine incursion between 6.3 and 4.3 million years ago. This resulted in the

Imperial Formation The Imperial Formation is the name of two distinct and unrelated geologic formations in North America, of different geologic Eras. Separate formations Canadian Paleozoic Era formation The older Imperial Formation occurs in the Northwest Territori ...

, composed of locally derived fossiliferous shallow marine sandstones and conglomerates that were deposited in a shallow inland sea across much of the Salton Trough. In the Coyote Mountains, these rocks were deposited directly on the older metamorphic and volcanic rocks. The Imperial Formation preserves many corals as well as shallow marine invertebrates and vertebrates.

Influence of the Colorado River Delta

The marine incursion of the ancestral

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...

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 The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Deguyños Formation of the

Imperial Group Imperial Brands plc (formerly Imperial Tobacco Group plc), is a British multinational tobacco company headquartered in Bristol, England. It is the world's fourth-largest international cigarette company measured by market share after Philip Mor ...

(formerly the

). The Deguyños Formation represents the distal prodelta portion of the Colorado River delta, and is characterized by upward-coarsening cycles of claystone, siltstone,

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

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. Erosion in Anza-Borrego

Recent uplift

The Coyote Mountains lies within a complex tectonic region. The Salton Trough itself is a pull-apart basin that is the result of crustal stretching and sinking by the combined actions of the

San Andreas Fault The San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizonta ...

and the

East Pacific Rise The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located alon ...

Tectonism Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

related to the North America – Pacific

plate boundary Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...

is primarily manifested by the

, the

, the Imperial Fault Zone, and the

San Jacinto Fault Zone The San Jacinto Fault Zone (SJFZ) is a major strike-slip fault zone that runs through San Bernardino, Riverside, San Diego, and Imperial Counties in Southern California. The SJFZ is a component of the larger San Andreas transform system and i ...

, as well as a complex system of interconnecting faults. These major right lateral strike-slip faults have transformed the region in geologically recent times. Within the last ≈1.2 million years, the Elsinore Fault Zone and its associated subordinate faults are responsible for rapidly uplifting metamorphic basement rocks and overlying volcanic and sedimentary rocks of the Coyote Mountains, revealing the complex stratigraphic record of their tectonic, climatic, and paleontological evolution. Marine fossils and sedimentary deposits that once formed in a shallow sea (ancestral Gulf of California) now sit at an elevation of over 2000 feet above sea level. This rapid uplift has also accelerated and facilitated increased erosion and weathering. Wind and rain carve steep canyons into the recently exposed rocks, and transport loose material downslope. Gravels derived from this erosion form terraces as old as the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

and as recent as the

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

(current epoch), which overlie all of the units in the Coyote Mountains. These terraces are further eroded and carved into by a system of active anastomosing drainages. On the north side of the Coyote Mountains, these drainages carve into the poorly

lithified Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithificatio ...

sediments of the Imperial and Palm Spring Groups, forming the Carrizo Badlands. These processes are ongoing and have continued throughout the past ≈1.2 million years. Sediments of the Imperial and Palm Spring Groups north of the Coyote Mountains are deformed by the recent uplift of the range. Brittle and ductile deformation of sediments in this area is consistent with prior interpretations of uplift and inversion of the Fish Creek–Vallecito basin as a result of initiation of the Elsinore and other strike-slip faults in the western Salton Trough ≈1.2 Ma (Dorsey et al., 2011). Continued right-lateral strike-slip motion on the Elsinore fault is accommodated by a network of ladder-like faults known as the Andradé ladder structure. This ≈7-km-wide fault structure is consistent with a zone of distributed right-lateral shear and rotation that accommodates the right-lateral deformation between the Elsinore and Painted Gorge faults.Smart, J.W. (2018) "Structural geology of the Eastern Carrizo Badlands, north of the Coyote Mountains, Southern California" https://csuchico-dspace.calstate.edu/handle/10211.3/211211

References

External links

Coyote Mountains Wilderness
- BLM {{Authority control Mountain ranges of the Colorado Desert Peninsular Ranges Mountain ranges of San Diego County, California Mountain ranges of Imperial County, California