Tracing outcrops in the High Sierras

DESOLATION WILDERNESS – Brittany Klemm (’14), Dai Wilson (’14), Kevin Alvarado (’16) and Dr Burmeister escaped the clutches of the Central Valley for another day in the high Sierra doing fieldwork in our Grass Lake study area in the Desolation Wilderness Area. Fortunately for us and our research, the Desolation Wilderness Area (which lies within the Eldorado National Forest) has apparently escaped the systemwide closures shutting off access to public lands. However, we were not the only ones benefiting from this reprieve – many of the people turned away from Yosemite are apparently relying on the the hike to the top of Mount Tallac to provide a much needed dose of outdoor medicine.

The goal of our quick trip was to explore some new methods for measuring deformation in the Grass Lake study area. While the preliminary results of geologic mapping by Pacific’s Structure & Tectonics Group in the Grass Lake area very interesting, finding a suitable method for measuring the total amount of deformation (strain) distributed throughout the rocks has proven challenging. This is due in large part to the size of the rock fragments in the conglomerate, which are larger than those normally involved in such analyses. Today, we tried a method suggested by our colleague, Allie Macho, at the University of Wisconsin. Allie’s method uses thick, transparent plastic sheeting and permanent markers to record shapes and arrangements of the various rock fragments in outcrop exposures. Once back in the lab, we’ll later use these tracings to produce images that can be imported into a computer for analysis.

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