D.E. Champion
M.A. Clynne
J. B. Lowenstern
A.M. Sarna-Wojcicki
J. L. Wooden
M. A. Lanphere
2004
<p><span>The age of the Rockland <a title="Learn more about Tephra from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tephra" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tephra">tephra</a>, which includes an <a title="Learn more about Ash Flow from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ash-flow" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ash-flow">ash-flow</a> <a title="Learn more about Tuff from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tuff" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tuff">tuff</a> south and west of Lassen Peak in northern <a title="Learn more about California from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/california" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/california">California</a> and a widespread ash-fall deposit that produced a distinct stratigraphic marker in western North <a title="Learn more about Americas from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/social-sciences/americas" data-mce-href="https://www.sciencedirect.com/topics/social-sciences/americas">America</a>, is constrained to 565,000 to 610,000 yr by </span><sup>40</sup><span>Ar/</span><sup>39</sup><span>Ar and U–Pb dating. </span><sup>40</sup><span>Ar/</span><sup>39</sup><span>Ar ages on <a title="Learn more about Plagioclase from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/plagioclase" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/plagioclase">plagioclase</a> from <a title="Learn more about Pumice from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/pumice" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/pumice">pumice</a> in the Rockland have a weighted mean age of 609,000 ± 7000 yr. Isotopic ages of spots on individual <a title="Learn more about Zircon from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/zircon" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/zircon">zircon</a> <a title="Learn more about Crystal from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/crystal" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/crystal">crystals</a>, analyzed by the SHRIMP-RG <a title="Learn more about Ion Microprobe from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ion-microprobe" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ion-microprobe">ion microprobe</a>, range from ∼500,000 to ∼800,000 yr; a <a title="Learn more about Subpopulation from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/subpopulation" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/subpopulation">subpopulation</a> representing crystal <a title="Learn more about Rim from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/rim" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/rim">rims</a> yielded a weighted-mean age of 573,000 ± 19,000 yr. Overall stratigraphic <a title="Learn more about Constraint from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/social-sciences/constraint" data-mce-href="https://www.sciencedirect.com/topics/social-sciences/constraint">constraints</a> on the age are provided by two volcanic units, including the underlying tephra of the <a title="Learn more about Lava from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/lava" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/lava">Lava</a> <a title="Learn more about Creek from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/creek" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/creek">Creek</a> Tuff erupted within Yellowstone <a title="Learn more about National Parks from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/social-sciences/national-parks" data-mce-href="https://www.sciencedirect.com/topics/social-sciences/national-parks">National Park</a> that has an age of 639,000 ± 2000 yr. The basaltic <a title="Learn more about Andesite from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/andesite" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/andesite">andesite</a> of Hootman Ranch stratigraphically overlies the Rockland in the Lassen Peak area and has </span><sup>40</sup><span>Ar/</span><sup>39</sup><span>Ar ages of 565,000 ± 29,000 and 565,000 ± 12,000 yr for plagioclase and groundmass, respectively. Identification of Rockland tephra in <a title="Learn more about Ocean Drilling Program from ScienceDirect's AI-generated Topic Pages" href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ocean-drilling-program" data-mce-href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ocean-drilling-program">ODP</a> core 1018 offshore of central California is an important stratigraphic age that also constrains the eruption age to between 580,000 and 600,000 yr.</span></p>
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10.1016/j.yqres.2004.03.001
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Age of the Rockland tephra, western USA
article