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Distinguishing and Correlating Deposits from Large Ignimbrite Eruptions Using Paleomagnetism: the Cougar Point Tuffs (Mid-Miocene), Southern Snake River Plain, Idaho, USA

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posted on 2016-07-26, 12:30 authored by David R. Finn, Robert S. Coe, Ethan Brown, Michael Branney, Marc K. Reichow, Thomas Knott, Michael Storey, Bill Bonnichsen
In this paper, we present paleomagnetic, geochemical, mineralogical, and geochronologic evidence for correlation of the mid-Miocene Cougar Point Tuff (CPT) in southwest Snake River Plain (SRP) of Idaho. The new stratigraphy presented here significantly reduces the frequency and increases the scale of known SRP ignimbrite eruptions. The CPT section exposed at the Black Rock Escarpment along the Bruneau River has been correlated eastward to the Brown's Bench escarpment (six common eruption units) and Cassia Mountains (three common eruption units) regions of southern Idaho. The CPT records an unusual pattern of geomagnetic field directions that provides the basis for robust stratigraphic correlations. Paleomagnetic characterization of eruption units based on geomagnetic field variation has a resolution on the order of a few centuries, providing a strong test of whether two deposits could have been emplaced from the same eruption or from temporally separate events. To obtain reliable paleomagnetic directions, the anisotropy of anhysteretic remanence was measured to correct for magnetic anisotropy, and an efficient new method was used to remove gyroremanence acquired during alternating field demagnetization.

History

Citation

Journal of Geophysical Research: Solid Earth, 2016, 121 (9), pp 6293-6314

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Geology

Version

  • VoR (Version of Record)

Published in

Journal of Geophysical Research: Solid Earth

Publisher

American Geophysical Union

issn

2169-9356

eissn

2169-9313

Copyright date

2016

Available date

2017-03-17

Publisher version

http://onlinelibrary.wiley.com/doi/10.1002/2016JB012984/abstract

Language

en

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