Newsletter 8, Geo-hike, Guadalupe with Boo Hoff and Cactus Spring Trails, November 4-5, 2022, Santa Rosa-San Jacinto National Monument, California
Backpack up the eastside of the Santa Rosa Mountains. Beautiful route with great geology.
Ginny and I made this hike up the east flank of the Santa Rosa Mountains from La Quinta to the Sawmill Mountain trailhead parking spot off Highway 74 . It took us two days and we camped one night just below the Cowboy Camp on a small flat with a great panorama of the Coachella Valley. It’s a beautiful route, with lots of spectacular views, a range of desert vegetation, and fascinating and well exposed geology. Keep in mind it’s a difficult hike with lots of elevation gain. If you plan on backpacking, you’ll need to carry water. Only water sources were near end of second day in two deep canyons at Horsethief Creek and an unnamed small creek. We each carried about 5 liters, we used most of that, and the weather was mild. I wouldn’t think of doing what we did if the lower slopes had highs in the upper 80s or more. The route we took combined three trails: the Boo Hoff out of La Quinta, the steep and remote Guadalupe, and the Cactus Spring that is less steep except for the last few miles. The Guadalupe trail is difficult to follow in places and you need to stay on the trail as the terrain is rugged and there are cacti everywhere. We got off trail several times but the gpx route posted on alltrails.com got us back on track, it was very useful. There are lot of cairns, very helpful too, but some are obscure or covered by recent plant growth and there are stretches of trail with none. Total distance we hiked was16.7 miles with 5,656 ft of elevation gain. I’m estimating if one stuck to the exact trail, which we didn’t always do, it would only be about 15 miles. We had difficulty finding the Guadalupe trail at the main saddle above the Cowboy Camp and we got to talking on an easy stretch of the Cactus Spring trail the follows a broad wash and really wandered off trail.
Geology: A spectacular and easy to see northeast-dipping detachment fault is present along the lower and middle elevation slopes on the eastside of the Santa Rosa Mountains. The detachment is a continuous structure and has several names in the geologic literature: Asbestos Mountain fault mostly north of Highway 74, the La Quinta fault (SDAG-SCGS, 2012; Todd et al., 1988), and the Coyote Canyon fault (Shervais and Kirkpatrick, 2016). Due to its low-dipping fault surface intersection with the rugged topography it has a sinuous map pattern as shown in a map in the SDAG-SCGS, 2012 guidebook. The fault system extends along the east flank of the Santa Rosa Mountains from just south of Palm Springs southward to at least the Rabbit-Villager Peaks ridge west of the Salton Sea. Movement occurred within the brittle-regime upper crust as evidenced by cataclastic rocks and slickensides within the fault zone and numerous smaller faults and fractures that increase in intensity closer to the fault surface (Shervais and Kirkpatrick, 2016). Fault movement occurred during the late Cenozoic age and is associated with the young extensional opening of the Coachella Valley and the North American-Pacific Plate boundary, i.e. the Gulf of California.
Guadalupe Trail-Boo Hoff Trail November 4th, we hiked up the Guadalupe-Boo Hoff trail where there are panoramas of La Quinta, east flank of the Santa Rosa Mountains, and much of the Coachella Valley. The higher you go the more of the valley you see and eventually the Salton Sea comes into view. The trail crosses the detachment in at least two places where the biggest clue is the change in rock type from granodiorite (aka tonalite) in the hanging wall to metamorphic rocks (schist and gneiss) in the footwall. In general, the granodiorite is a lighter color than the underlying metamorphic rocks. It’s also possible to make out the fault zone that is characterized by lots of shearing, indurated fault gouge, and a metamorphic carapace with striations just below the fault zone. Ginny, who is not a geologist, spotted the fault zone pretty fast based on her hiking with me in nearby Coyote Canyon where the detachment is well exposed (Shervais and Kirkpatrick, 2016). Below are links to several videos I made along the way, it’s easier to appreciate what I am describing with a field video.
Panoramas of La Quinta, east flank of the Santa Rosa Mountains, and Coachella Valley. Very brief discussion of the detachment faults that dip towards the Coachella Valley with granodiorite in the hanging wall and the metamorphic Palm Canyon sequence in the footwall:
Close up of the detachment fault zone along the Guadalupe-Boo Hoff trail:
Further along the Guadalupe-Boo Hoff trail and more on detachment faults:
Backcountry campsite along Guadalupe trail. Video shows geology, terrain, and plants along the east flank of the Santa Rosa Mountains. Nice little flat spot about half mile before Cowboy camp. Ginny picked it because it was the first wide spot and we were pretty worn out. If it had been windy the Cowboy Camp would be a better choice:
Cactus Spring trail and geology, November 5 near Horsethief Creek:
Near the end of our two-day Geo-hike up the eastside of the Santa Rosa Mountains (total distance we hiked was16.7 miles with 5,656 ft of elevation gain). Video shows end of the Cactus Spring trail (or start if you do from the Sawmill trailhead), Martinez Mountain, panorama to the north across Highway 74. Still need to figure out what the white rock is. Possibly dolomite.
References:
SDAG-SCGS, 2012, (San Diego Association of Geologists and South Coast Geological Society (latest edition), Palms to Pines, Geological and Historical Excursions Through the Palm Springs Region, Riverside County, CA, SDAG (2008, 2009) and SCGS Volume 39 (2012), eds. S.Synder (2008), B. Miller-Hicks (2009), and J.A. Miller (2012), Distributed by Sunbelt Publications, www.sunbeltpub.com, 249 p. You can purchase at the Santa Rosa-San Jacinto Mountains National Monument visitor center in Palm Desert, CA.
Shervais, Katherine A.H. and James D. Kirkpatrick, 2016, Smoothing and re-roughening processes: The geometric evolution of a single fault zone. Journal of Structural Geology 91: 130-143.
Todd, V.R., B.G. Erskine, and D.M. Morton, 1988, Metamorphic and tectonic evolution of the northern Peninsular Ranges batholith, southern California, in Metamorphism and Crustal Evolution of the Western United States, Rubey v. VII, ed., W.G.Ernst, p. 894-937, Prentice-Hall, Englewood Cliffs, NJ.
THOMAS L. DAVIS PHD PG & ASSOCIATES LEAD AND ORGANIZE GEOLOGIC FIELD TRIPS IN THE SOUTHWESTERN USA AND BAJA CALIFORNIA FOR ORGANIZATIONS, COMPANIES, AND INDIVIDUALS, CONTACT US AT