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Still holding on to the belief that rocks are cool, too................ Geologic History of Joshua Tree National Park The mountains and basins of Joshua Tree National Park contain uniquely detailed and complete records of the crustal evolution of southern California. A collaborative effort with Professor Drew Coleman (University of North Carolina), Dr. Joe Wooden (USGS), and Professors Lawford Anderson and Scott Paterson (University of Southern California) is designed to compile a geologic map and geologic history of the park. To learn more about the park, please visit our website. Proterozoic Metamorphism in California The mountains of southern California contain tremendous exposures of the Proterozoic and Mesozoic basement of California. A joint project with Professor Drew Coleman (University of North Carolina) and Dr. Joe Wooden (USGS) is designed to investigate the tectonic setting and processes of formation of continental crust in California.
Marilyn (Stanford University), Kim, Paul, Sara, Helen, and Janet at Keys View We use field mapping as the basis for petrologic and geochronologic studies of these complexly deformed and multiply-metamorphosed Proterozoic basement rocks.
Shown here are a few zircons from an augen gneiss, showing dark, 1.7 billion year old cores which partially dissolved and were overgrown by lighter rims 500 million years later, about 1.2 billion years ago. The rock cycle can be really slow.............. Tectonics of California in the Late Cretaceous The lowest structural levels of the crust in southern California, however, turn out to be some of the youngest rocks. Weird, eh? A joint project with Professor Carl Jacobson (Iowa State University) and Dr. Marty Grove (UCLA) is designed to investigate the tectonic setting and processes of formation of these lower crustal rocks.
Shown here is a zircon from the Pelona - Orocopia - Rand Schist, showing lovely oscillatory zoning, eroded from an igneous rock formed about 90 million years ago. This schist was originally deposited as a sedimentary rock (the sedimentary protolith), buried to a depth of about 30 kilometers and metamorphosed, and then exhumed back to within a few kilometers of the surface of the Earth by 80 million years ago. All this in <10 million years. The rock cycle can be really fast.............. Sulfur and Carbon in Granitic Rocks Coming soon......
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