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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 95, NO. B1, PAGES 625-647, JANUARY 10, 1990 Paleomagnetismof Middle Miocene Volcanic Rocks in the Mojave-Sonora
 

Summary: JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 95, NO. B1, PAGES 625-647, JANUARY 10, 1990
Paleomagnetismof Middle Miocene Volcanic Rocks in the Mojave-Sonora
Desert Region of Western Arizona and Southeastern California
GARY J. CALDERONE
U.S. Geological Survey, Flagstaff, Arizona
ROBERT F. BUTLER AND GARY D. ACTON 1
Department of Geosciences,Universityof Arizona, Tucson
Paleomagneticdirectionshave been obtainedfrom 190early to middle Miocene (12-20 Ma) mafic
volcanic flows in 16 mountain rangesin the Mojave-Sonora desert region of western Arizona and
southeasternCalifornia. These flows generally postdate early Miocene tectonic deformation accom-
modatedby low-anglenormalfaultsbut predatehigh-anglenormalfaultingin the region.After detailed
demagnetization experiments, 179 flows yielded characteristic directions interpreted as original
thermal remanent magnetizations(TRM). Becauseof the episodicnature of basalticvolcanism in this
region, the 179 flows yielded only 65 time-distinctvirtual geomagneticpoles (VGPs). The angular
dispersionof the 65 VGPs is consistentwith the angular dispersionexpected for a data set that has
adequately averagedgeomagneticsecularvariation. The paleomagneticpole calculatedfrom the 65
coolingunit VGPs is located at 85.5°N, 108.9°Ewithin a 4.4°circle of 95% confidence.This pole is
statisticallyindistinguishable(at 95% confidence)from referencepolescalculatedfrom rocksof similar
agein stableNorth America andfrom a paleomagneticpole calculatedfrom rocksof similaragein Baja
California. The coincidence of paleomagnetic poles from the Mojave-Sonora desert region with

  

Source: Acton, Gary - Department of Geology, University of California, Davis

 

Collections: Geosciences