(1) U.S Geological Survey Professional Paper 1812, by Wes Hildreth and Judy Fierstein, “Eruptive History of Mammoth Mountain and its Mafic Periphery, California,” is available online at https://pubs.er.usgs.gov/pu
For paper copies, contact Judy Fierstein (jfierstn@xxxxxxxx)
USGS Professional Paper 1812 includes a new geologic map of the Long Valley Caldera, Mammoth Mountain, and the Middle Fork canyon of the San Joaquin River including Devils Postpile National Monument, recounts the geologic and volcanic history of the area east of the Sierra Nevada in California in far greater detail than any previously published report.
This report and accompanying geologic map portray the eruptive history of Mammoth Mountain and a surrounding array of contemporaneous volcanic units that erupted in its near periphery. The moderately alkaline Mammoth eruptive suite, basaltic to rhyodacitic, represents a discrete new magmatic system, less than 250,000 years old, that followed decline of the subalkaline rhyolitic system active beneath adjacent Long Valley Caldera since 2.2 Ma (Hildreth, 2004). The scattered vent array of the Mammoth system, 10 by 20 km wide, is unrelated to the rangefront fault zone, and its broad nonlinear footprint ignores both Long Valley Caldera and the younger Mono-Inyo rangefront vent alignment.
Suggested Citation:
Hildreth, Wes, and Fierstein, Judy, 2016, Eruptive history of Mammoth Mountain and its mafic periphery, California: U.S. Geological Survey Professional Paper 1812, 128 p., 2 plates, scale 1:24,000, http://www.dx.doi.org/10.3133/pp1812 .
(2) USGS Scientific Investigations Report 2016-5120, Long Valley Caldera Lake and Reincision of Owens River Gorge, by Wes Hildreth and Judy Fierstein, is now available online at: https://doi.org/10.3133/s
Printed copies will be available through the authors (Wes Hildreth: hildreth@xxxxxxxx; Judy Fierstein: jfierstn@xxxxxxxx)
After collapse of Long Valley caldera during pyroclastic eruption of the Bishop Tuff at 767 ka, a long-lived lake collected in the depression and persisted throughout much (but not all) of the middle Pleistocene. Much of the western half of the caldera floor was soon covered by thick and voluminous lavas and tuffs of what Bailey and others (1976) called the Early Rhyolite (~750–640 ka), most of which were faulted and uplifted resurgently, thereafter confining the lake to the eastern half of the caldera floor. Just southeast of the caldera, Owens River Gorge was eroded through the Volcanic Tableland, a south-sloping ignimbrite plateau that is a principal sector of the Bishop Tuff outflow sheet. It has been widely assumed that cutting of Owens Gorge drained the intracaldera lake, either by overflow or by headward erosion. But neither the timing nor process of extinction of the lake nor the complex history of gorge excavation has been adequately established. In the present investigation, we mapped in detail the caldera and gorge at a scale of 1:24,000, reexamined previous interpretations, and developed several new data sets that bear upon both lake and gorge. As college classes and professional field excursions have highlighted this region for decades, the Owens River Gorge has become as iconic as the Bishop Tuff.
Suggested citation:
Hildreth, Wes, and Fierstein, Judy, 2016, Long Valley Caldera lake and reincision of Owens River Gorge: U.S. Geological Survey Scientific Investigations Report 2016–5120, 63 p., https://doi.org/10.3133/si
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