Sierras Field Trip Guide By: Aaron Powers, Ben Melosh, Nate Abramson, Peter Mueller-Wille, Sheldon Blair Painting by Albert Bierstadt

BRING: standard field equipment (brunton, pencils, pens, notebooks, protractor, ruler, and protection from the elements), TENT, breakfast and lunch for the first day AT LEAST (we’ll stop at a supermarket after the first day’s work), $3 for campsite, and anything else you think you might need for an overnight with this class.

Leave campus parking lot at 7am Arrive at locale 1 around 12:30pm or so Map the non-coaxial deformation in the Merced Falls Shale Set up camp at Don Pedro Lake etc. Don Pedro Lake Locale 1

Stop 1: Hell Hollow overview of Merced River Valley (view of Mother Lode topography, Melones fault zone, and geology!) Stop 2: Walk along a road cut exposing the Mother Lode vein system. Stop 3: More fault vein exposures near Oro Rico Mine. Stop 4: Basaltic Pillow lavas; note the tectonite fabrics! Stop 5: Overview of the Harvard Pit Mine Empire Mine, Grass Valley (Sibson & Elliot, 1993)

Cross Section Through Pine Tree Mine, Hells Hollow (Sibson & Elliot, 1993)

Regional Geologic History & Tectonics Begins with deposition of marine sediments in Jurassic that forms pre- Merced Falls Fmtn. Shales Mid-Jurassic, the region underwent uplift and granitic magmas were intruded into the area, metmorphosing the shale into schists and generating the regional serpentine and greenstone belts. Late-Jurassic to Early-Cretaceous, more uplift and deformation of entire region. Mid-Cretaceous to Quaternary, a long period of erosion and uplift, resulting in the exposure of the Mother Lode vein system. Regional geologic map (Sibson & Elliot, 1993)

Salt Springs/Merced Falls Formation: Jurassic in age and located in the western metamorphic belt of California. Shale composed of sericite, greywacke, tuffs, and conglomerate (mainly dark grey in color with some mica schist). Fossils are rarely found in this formation. This formation was originally shale that was metamorphosed during continental accretion (mid- Jurassic orogenies). This formation is bounded on its east side by the Copper Hill Volcanics that are of mid-Jurassic age. Deformed Shale in Connecticut Picture taken from

Resources 1. “Geology and Soils.” Prepared by GeoSolutions, 2002, a.us/publish/planning/tuscanyhills/Tuscany%2520Hills%2520Draft%252 0EIR/Chapters/Ch%25204/Ch% /4.5_Geology.pdf+%22Merced+Falls+Formation%22&hl=en&client=saf ari 2. Elliot, James and Rick Sibson. “Field Trip to the Southern Mother Lode.” Fish Camp California, Jenkins, Olaf P. “Geologic Guidebook Along Highway 49-Sierran Gold Belt: The Mother Lode Country.” 1948 Horray for deformation!