Newsletter 9, Nordhoff Peak Geo-hike via the Pratt Trail, southern California

Hiking across the Matilija Overturn

A small group of Geo-hikers hiked to the top of Nordhoff Peak (elev. 4426 ft) above Ojai California on November 25, 2022 via the Pratt Trail. The route is nearly 12 miles roundtrip with about 3700 ft elevation gain, not the easiest of hikes but the views of the Santa Ynez Range, Ojai Valley, western Santa Monica Mountains, and the Pacific Ocean with seven of the eight Channel Island is hard to beat. Weather was perfect with little wind, in the mid-60s, and sunny. The trail climbs up through steeply-dipping strata (rock layers) of the Matilija Overturn (youngest layers lie below older layers). The trailhead is in red-beds of the nonmarine Sespe Formation (Oligocene) and the route ascends north-dipping sedimentary rocks that are outcropping in reverse stratigraphic order (oldest on top). Above the Sespe Formation the trail crosses sandstone of the Eocene Coldwater Formation, siltstone and shale of the Cozy Dell Formation, and very resistant sandstone of the Matilija Formation, and near the crest of the Nordhoff ridge line sandstone, siltstone, and shale of the Eocene-Paleocene Juncal Formation. Normally, a trail that crosses strata dipping into the hillside takes the hiker into younger and younger rocks with the climb but at Matilija Overturn takes the hiker into older and older rocks with the climb.

The Coldwater is a shallow marine deposit, here and there with layers of oyster shell fragments. The older formations are deep-marine turbidite deposits. The Matilija Overturn is the south limb of the Santa Ynez Range anticlinorium that is the result if north-south crustal shortening in the western Transverse Ranges of southern California during the Pliocene and Quaternary; this shortening remains tectonically active.

Pratt Trail is shown below in red on portions of the Matilija and Ojai 7.5’ quadrangle maps. Paper geologic maps of the quads can be purchased from the Santa Barbara Museum Natural Nature:

https://www.sbnaturestore.org/products/matilija-quadrangle-df12?_pos=1&_psq=Mati&_ss=e&_v=1.0

https://www.sbnaturestore.org/products/ojai-quadrangle-df13?_pos=1&_psq=Ojai&_ss=e&_v=1.0

Jay Namson’s cross section (crustal side view) across the Ventura Basin and western Transverse Ranges. Nordhoff Peak is located below the label “Santa Ynez Mountains.” Additional SoCal Cross Sections at http://www.geologicmapsfoundation.org/library-xsections-usa.html. Keep in mind the contact info shown is long out of date, use geologicmapsfoundation@gmail.com

At the top of Nordhoff were a hang-gliding club using the the steep south-side of the peak as a launch point. It was fascinating to watch the set-up, organization and commands, and take-off.

Geo-hike part way up the Pratt Trail. Short discussion of the geology and panorama

Intersection of Pratt Trail and Nordhoff Ridge Road. Near Nordhoff Peak. Video has a short discussion of the panorama and geology.

Watch hang-gliders prepare and take-off from Nordhoff Peak above Ojai-video A.

Panorama and geology discussion from old fire tower at Nordhoff Peak.

Watch hang-gliders prepare and take-off from Nordhoff Peak above Ojai-video B.

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 tldavisgeo@gmail.com or geologicmapsfoundation@gmail.com