Klamath Mountains - first half

First Half of Field Trip

The 25th Annual Fall Field Frolic

August 17 - 22, 2007

Field Trip Leaders:

Doug Yule, Elena Miranda, Dave Liggett

First Half of Fall 2007 Dept Trip

Photos and text by Dave Liggett

	On Day one we drove from CSUN to Ashland, Oregon. The following morning Dr. Yule gave an overview of the regional geology of the Klamath mountains including a description of the development of the Josephine marginal basin which he worked on for his Ph.D. This field trip looks at selected stops within his field area as well as some features in the surrounding region.
	We drove past Mt. Ashland, a 161Ma granodiorite, and stopped at an overlook for a photo op of Mt. Shasta.
	On a ridge between Mt. Ashland and Applegate reservoir we collected a variety of rocks and discussed their composition and metamorphic grade.
	This road cut at Applegate reservoir is part of the western Hayfork terrane and consists of volcanogenic meta-sandstone (173 Ma) and meta-argillite that are cross cut by andesite dikes (156 Ma).
	Dr. Miranda explains the difference between fertile and depleted mantle.
	We camped at Josephine Campground. Rain during the night and morning caused us to modify a planned 12 mile hike to Pearsol Peak.
	View to the NE looking across the Illinois River valley along the boundary between serpentinized Josephine peridotite and rocks of the western Paleozoic belt (photo and caption by D. Yule).
	On the road to Onion Camp we stopped to examine the slaty meta-argillites and the massive, polylithologic, ophiolite clast breccia of the Fiddler Mountain olistostrome complex. They occur at the base of the cover sequence.
	Group photo in the saddle above Onion Camp. At this stop we looked at massive metabasalt of the Onion Camp complex. Features in these rocks are similar to those in the Rattlesnake Creek terrane which lies on the opposite side of the marginal basin. The Onion Camp complex and the Fiddler Mountain olistostrome represent a portion of the remnant arc that was rifted during the formation of the Josephine ophiolite.
	On the road to Store Creek we stopped to look at a road cut of Josephine peridotite. The foliation in the peridotite probably resulted from the closing of the back arc basin but is not as deformed or altered as much as the remnant arc rocks. Here a ~150 Ma felsic dike cuts the serpentinized peridotite.
	Near Six Mile Camp we looked at the Rogue Formation. These rock represent the active arc complex.

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