Sierra Crest Graben: a Miocene Walker Lane Pull-apart in the Ancestral Cascades Arc at Sonora Pass

INTRODUCTION This paper was prepared for the National Association of Geoscience Teachers Far Western Section Fall Conference, High Sierra Institute, Baker Station, Sierra Nevada September 7 9, 2012. The maps and map interpretations in this document (Figures 1, 2, 3, 4, 5) form about a fourth of a much larger map and manuscript that have been peer reviewed by David John of the U.S. Geological Survey and Elizabeth Miller of Stanford University (Busby et al., in prep). The material presented here focuses on geologic maps and map interpretations for the Sonora Pass area, in the hope that this will be a resource to teachers who would like to bring students to Sonora Pass for future geologic mapping exercises. The Sonora Pass area forms a relatively accessible part of the Sierran crest, because Highway 108 runs through it (Figure 3). This paper describes all of the Sonora Pass area, which took us several years to map in its entirety, while the one-day field trip will be a single traverse between Sonora Pass and Sonora Peak (Figure 4A). In addition, I have posted a pdf file of my lecture powerpoint online. This provides a full set of color figures geologic setting and geology of the region, which are too costly to print, along with bullet point interpretations. These are available at: http://www.geol.ucsb.edu/faculty/busby/NAGT2012