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Field Trips

2015 SDAG Field Trip - Western Salton Trough Regional Tectonics,
Coyote Mountains and Vicinity

November 6 - 8, 2015

2015 field trip area

Trip 2015 group photo The 2015 San Diego Association of Geologists annual field trip explored the tectonics and geology of the Coyote Mountains in the western Salton Trough. The field trip was lead in part by Ann Byker-Koofman 0f Chino State University who has been mapping in the Coyote Mountians for several years. Also leading the field trip were George Morgan and Jr Morgan who have also been mapping at 1:2000 scale in the Coyote Mountains for several years. From this mapping new ideas and interpretations of the geology of Coyote Mountains have been produced. A few of the geomorphic forms we see in the Coyote Mountains are: an outlier (klippe?) made from the detachment faults, mullion structures on faults, hoodoos in tuff beds, transgressional and regrestional sequence(8+), horst and graben structures, cuesta, stripped dip-slopes, slot canyons cinder cones and volcanic plugs.

  Montek passes knowledge to the younger generation.
Monte and young friend
Trip 2015
Friday, November 6: Meet at the Community Park on S2, 2.2 miles northwest of Ocotillo. Leave at 10:30 am for an OPTIONAL hike in the Domelands area or Fossil Canyon. The long hike to the Domelands will be on and off trails on rugged terrain at least 6 miles long, and may take up to 6 hours to complete. The Fossil Canyon hike will be about 2 miles long take up to 4 hours and will keep to relatively low relief areas. Check in will be open in the evening by 5pm (approximate sunset). No meals provided on Friday.

Trip 2015 sed Trip 2015
Saturday, November 7: Meet at Ocotillo Community Park. Check in starts at 6:00 am. After a continental breakfast, we will travel by car caravan to see the geologic and tectonic features of the southern and eastern flanks of the Coyote Mountains. Our campsite will be at the Ocotillo Community Park. Although there are no showers, there are separate bathroom facilities and a kitchen large room in the community center building.

There will be seating in the 4WD vehicles going up the hill for those that do not have a 4WD. Drivers of 4WD vehicles let us know how many empty seats you have.

There will be two alternate field trip routes on Saturday. Alternative 1 (High Road): One will travel to the top of the Coyote Mountains via Painted Gorge High Road and out to an overlook above Fossil Canyon. This alternative will be over very rugged roads that require high-ground clearance 4WD vehicles. Due to the short daylight hours in November, people going on this will need to meet at the Painted Gorge Kiosk by 7:30 am. Alternative 2 (Low Road): The other field trip route will be along the southern and eastern flanks of the Coyote Mountains on "typical" dirt roads of the backcountry. We will look at features of the Elsinore fault zone and the Paleozoic to Quaternary geologic units making up the Coyote Mountains.

Sunday, November 8: After a full breakfast in camp, we will depart the Ocotillo Community Park camp site. There will be two alternate field trip routes on Sunday. Alternative 1 (Low Road): This field trip route will include a stop at the Painted Gorge Wash fault and partially retrace the "low road" route of Alternative 2 of Saturday. Lunch will be provided on the route. The last stop will wrap up around 3 pm, well before sunset. Those who need to depart early have the option to break away around noon. Alternative 2 (High Road): This field trip route will retrace the "high road" route of Alternative 1 of Saturday. With an early start, the group will be back down the mountain by 3pm. A bag lunch will be provided. There will be no option for early departure.

The Community Park will be available for camping Sunday night. No meals are provided after Sunday lunch.

Another High Road opportunity will be available on Saturday, November 14, led by George Morgan. This opportunity is self-supported. No meals, beverages, or other logistical services will be provided by SDAG.
windcave field trip

Background information

The oldest units found in the Coyote Mountains are in the metamorphic section that is made of marbles, amphibolites, schists, cherts, and quartzites. These units represent Paleozoic(?) age miogeoclinal to flysch sediments that were deposited in a passive continental margin in the state of Sonora, Mexico. Starting before or during the Jurassic, the passive margin in Sonora, Mexico became an active continental margin and the sediments were intruded, deformed, and metamorphosed. Some of igneous units associated with the active margin are: diorite, gabbro, dikes of various compositions, foliated tonalite, and the White Cross Gneiss. All of these units are Jurassic (~162 Ma). The deformation has completely destroyed most of the original sedimentary relationships between the protoliths of the marbles, schist, quartzites, cherts, and amphibolites. The metamorphics have been left with steep foliation and tight folds.

After an interval, when no Cretaceous to Oligocene rocks were preserved in the Coyote Mountains, Basin and Range extension took place in Sonora, Mexico. In the Coyote Mountains the sedimentary and volcanic rocks that record this activity were deposited in extensional basins. These rocks include: 1) White and Red Fanglomerates (Early Miocene), with the Red Fanglomerate interfingering with the Alverson Formation; 2) Alverson Formation (~17 Ma) (Early Miocene) consisting of basalt and andesite flows, dikes, plugs, tuffs, lahars, and pyroclastics, with basalt flows high in the upper Alverson (younger than ~16.9 Ma) interfingering with Imperial Group sediments; 3) marine and non-marine rocks of the lower Imperial Group, the Viejo Formation, a proposed new formation of the Imperial Group, Early(?) Miocene to Pliocene.

During the deposition of the Imperial Group sediments the in Coyote Mountains, the tectonics changed from Basin and Range extension to extension associated with the right-lateral transtension associated with the San Andreas fault. During Imperial Group deposition, the Coyote Mountains started to move to the north-west and came under the depositional influence of the Colorado River. The wide spread Deguynos Formation, the upper part of the Imperial Group, and the non-marine, wide spread, Palm Spring Group (Pliocene to Pleistocene) sediments in the Coyote Mountains record this change in tectonics and sedimentation.

The Coyote Mountains are now located in the western part of the Salton Trough, dominated by right-lateral faulting and are being differentially uplifted.

The types of faults found in the Coyote Mountains are: active right-lateral faults (Elsinore and related faults), active left-lateral faults (Painted Gorge Wash and related faults), detachment faults, high-angle normal faults, and thrust faults.

Field Trip Organizer - 2015 SDAG Vice President Randy Wagner (760) 877-3490

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