Paleomagnetism and K-Ar ages of volcanic rocks from Long Valley caldera, California

Journal of Geophysical Research B: Solid Earth
By: , and 

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Abstract

Paleomagnetic measurements and K‐Ar age determinations on volcanic rocks from Long Valley caldera, California, have enabled further refinement of eruptive activity within this large silicic volcanic center. K‐Ar age determinations show that postcaldera volcanic eruptions began 0.73 m.y. ago and continued periodically until about 50,000 years ago. The eruptions were not temporally random but tended to occur in distinct episodes separated by periods of quiescence. Volcanism in the western half of the caldera was particularly intense between 0.15 and 0.50 m.y. ago, when many units ranging in composition from basalt to rhyolite were erupted. An average of the virtual geomagnetic poles for 33 units from the caldera yields a paleomagnetic pole at 89.7°N, 138.4°E, (α95 = 5.1°), which is indistinguishable from the earth's rotational axis. The ancient geomagnetic field dispersion about this mean pole is 16.0°, with upper and lower limits of 19.3° and 13.6°, respectively.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Paleomagnetism and K-Ar ages of volcanic rocks from Long Valley caldera, California
Series title Journal of Geophysical Research B: Solid Earth
DOI 10.1029/JB091iB01p00633
Volume 91
Issue B1
Year Published 1986
Language English
Publisher AGU
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 20 p.
First page 633
Last page 652
Country United States
State California
Other Geospatial Long Valley Caldera