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John King

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Mammoth Mountain is a dacitic dome complex located on the southwestern rim of Long Valley Caldera, California. Mammoth Mountain has exhibited unrest over the past ~30 years, characterized by seismicity over a broad range of depths, elevated 3He/4He ratios in fumarolic gas and large-scale diffuse CO2 emissions. Monitoring of this unrest has included collection of fumarole gas samples for geochemical analysis and tree cores for radiocarbon analysis of annual growth rings. This report updates the long-term geochemical record at Mammoth Mountain, compiling the chemical and isotopic (d13C-CO2, 3He/4He) compositions of 59 gas samples collected from Mammoth Mountain fumarole from 1998 to 2016. In addition, we report radiocarbon...
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Radiocarbon dating of silicified wood was performed at the U.S. Geological Survey’s Radiocarbon Laboratory in Denver, Colorado. All samples were chemically treated using the standard acid-base-acid (ABA) procedure before being combusted online in the presence of excess high-purity oxygen. Water and other contaminant gases were removed using cryogenic separation techniques, and the resulting purified CO2 gas was measured manometrically and converted to graphite using an iron catalyst and hydrogen reduction (Vogel et al., 1984). Graphite targets were then submitted for accelerator mass spectrometry 14C analysis at the National Ocean Sciences Accelerator Mass Spectrometry facility in Woods Hole, Massachusetts. All...
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Silicified wood samples were vacuum impregnated with epoxy, sectioned, and sputter coated with 10 nm Au/Pd at the U.S. Geological Survey, Menlo Park, CA. Samples were imaged in a Tescan VEGA3 Scanning Electron Microscope (SEM) equipped with an Oxford 150 mm2 X-MaxN large area energy dispersive spectrometer at the U.S. Geological Survey, Menlo Park, CA. Backscatter (BSE) images were collected with an accelerating voltage (HV) of 30 kV and a working distance (WD) of ~15 mm. Magnification is indicated on individual images. The data files for Scanning Electron Microsocopy (SEM) contain representative SEM-BSE images of samples OFL101 and OFL103-2. This research was conducted under Yellowstone Research Permit YELL-SCI-8030.
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Silicified wood from around Old Faithful Geyser, Yellowstone National Park
Old Faithful Geyser in the Upper Geyser Basin of Yellowstone National Park is one of the best studied geysers in the world. Under research permit YELL-SCI-8030, samples from 13 silicified tree remnants were collected adjacent to the Old Faithful Geyser cone in April and November 2019. The silicified wood samples were dated using the radiocarbon (14C) method and were analyzed by scanning electron microscope (SEM) to determine the extent of wood silicification. This study was conducted in order to provide new information on the geyser’s past decadal to centennial eruptive activity. Understanding Old Faithful’s past could provide a baseline for understanding future changes in its eruption intervals.
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