Argon geochronology of late Pleistocene to Holocene Westdahl volcano, Unimak Island, Alaska

Calvert, Andrew T.; Moore, Richard B.; McGimsey, Robert G.

Abstract:

High-precision 40Ar/39Ar geochronology of selected lavas from Westdahl Volcano places time constraints on several key prehistoric eruptive phases of this large active volcano. A dike cutting old pyroclastic-flow and associated lahar deposits from a precursor volcano yields an age of 1,654+/-11 k.y., dating this precursor volcano as older than early Pleistocene. A total of 11 geographically distributed lavas with ages ranging from 47+/-14 to 127+/-2 k.y. date construction of the Westdahl volcanic center. Lava flows cut by an apparent caldera-rim structure yielded ages of 81+/-5 and 121+/-8 k.y., placing a maximum date of 81 ka on caldera formation. Late Pleistocene and Holocene lavas fill the caldera, but most of them are obscured by the large summit icecap.

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USGS Numbered Series

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72826

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Calvert, Andrew T.; Moore, Richard B.; McGimsey, Robert G.

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ENGLISH

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Studies by the U.S. Geological Survey in Alaska, 2004

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16 p.

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Professional Paper

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1709-D

Citation Search Results Text:

Argon geochronology of late Pleistocene to Holocene Westdahl volcano, Unimak Island, Alaska; 2005; PP; 1709-D; USGS NUMBERED SERIES; Studies by the U.S. Geological Survey in Alaska, 2004; Calvert, Andrew T.; Moore, Richard B.; McGimsey, Robert G.