Paleomagnetism of Miocene volcanic rocks in the Mojave-Sonora desert region, Arizona and California.

Persistent Link:
http://hdl.handle.net/10150/184554
Title:
Paleomagnetism of Miocene volcanic rocks in the Mojave-Sonora desert region, Arizona and California.
Author:
Calderone, Gary Jude.
Issue Date:
1988
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Paleomagnetic directions have been obtained from 190 Middle Miocene (12-20 Ma) mafic volcanic flows in 16 mountain ranges in the Mojave-Sonora desert region of western Arizona and southeastern California. These flows generally postdate Early Miocene tectonic deformation accommodated by low-angle normal faults but predate high-angle normal faulting in the region. After detailed magnetic cleaning experiments, 179 flows yielded characteristic thermal remanent magnetism (TRM) directions. Because of the episodic nature of basaltic volcanism in this region, the 179 flows yield only 65 time-distinct virtual geomagnetic poles (VGPs). The angular dispersion of the VGPs is consistent with the angular dispersion expected for a data set that has adequately averaged geomagnetic secular variation. The paleomagnetic pole calculated from the 65 cooling unit VGPs is located at 85.5°N, 108.9°E within a 4.4° circle of 95% confidence. This pole is statistically indistinguishable (at 95% confidence) from reference poles calculated from similar-age rocks in stable North America and from a paleomagnetic pole calculated from similar-age rocks in Baja and southern California. From the coincidence of paleomagnetic poles from the Mojave-Sonora and adjacent areas, we can conclude that: (1) vertical-axis tectonic rotations have not accompanied high-angle normal faulting in this region; (2) there has been no latitudinal transport of the region since 12-20 Ma; and (3) long-term nondipole components of the Miocene geomagnetic field probably were no larger than those of the recent (0-5 Ma) geomagnetic field. In contrast, paleomagnetic data of other workers indicate vertical-axis rotations of similar-age rocks in the Transverse Ranges, the Eastern Transverse Ranges, and the Mojave Block. We speculate that a major discontinuity in the vicinity of the southeastward projection of the Death Valley Fault Zone separates western areas affected by vertical-axis rotations from eastern areas that have not experienced such rotations.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Paleomagnetism -- California -- Mojave Desert.; Volcanic ash, tuff, etc. -- California -- Mojave Desert.; Volcanic ash, tuff, etc. -- Sonoran Desert.; Geology, Stratigraphic -- Miocene.; Paleomagnetism -- Sonoran Desert.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Butler, Robert F.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titlePaleomagnetism of Miocene volcanic rocks in the Mojave-Sonora desert region, Arizona and California.en_US
dc.creatorCalderone, Gary Jude.en_US
dc.contributor.authorCalderone, Gary Jude.en_US
dc.date.issued1988en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractPaleomagnetic directions have been obtained from 190 Middle Miocene (12-20 Ma) mafic volcanic flows in 16 mountain ranges in the Mojave-Sonora desert region of western Arizona and southeastern California. These flows generally postdate Early Miocene tectonic deformation accommodated by low-angle normal faults but predate high-angle normal faulting in the region. After detailed magnetic cleaning experiments, 179 flows yielded characteristic thermal remanent magnetism (TRM) directions. Because of the episodic nature of basaltic volcanism in this region, the 179 flows yield only 65 time-distinct virtual geomagnetic poles (VGPs). The angular dispersion of the VGPs is consistent with the angular dispersion expected for a data set that has adequately averaged geomagnetic secular variation. The paleomagnetic pole calculated from the 65 cooling unit VGPs is located at 85.5°N, 108.9°E within a 4.4° circle of 95% confidence. This pole is statistically indistinguishable (at 95% confidence) from reference poles calculated from similar-age rocks in stable North America and from a paleomagnetic pole calculated from similar-age rocks in Baja and southern California. From the coincidence of paleomagnetic poles from the Mojave-Sonora and adjacent areas, we can conclude that: (1) vertical-axis tectonic rotations have not accompanied high-angle normal faulting in this region; (2) there has been no latitudinal transport of the region since 12-20 Ma; and (3) long-term nondipole components of the Miocene geomagnetic field probably were no larger than those of the recent (0-5 Ma) geomagnetic field. In contrast, paleomagnetic data of other workers indicate vertical-axis rotations of similar-age rocks in the Transverse Ranges, the Eastern Transverse Ranges, and the Mojave Block. We speculate that a major discontinuity in the vicinity of the southeastward projection of the Death Valley Fault Zone separates western areas affected by vertical-axis rotations from eastern areas that have not experienced such rotations.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPaleomagnetism -- California -- Mojave Desert.en_US
dc.subjectVolcanic ash, tuff, etc. -- California -- Mojave Desert.en_US
dc.subjectVolcanic ash, tuff, etc. -- Sonoran Desert.en_US
dc.subjectGeology, Stratigraphic -- Miocene.en_US
dc.subjectPaleomagnetism -- Sonoran Desert.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorButler, Robert F.en_US
dc.contributor.committeememberRichardson, Randall M.en_US
dc.contributor.committeememberReynolds, Steveen_US
dc.contributor.committeememberChase, Clementen_US
dc.contributor.committeememberWallace, Terryen_US
dc.identifier.proquest8905909en_US
dc.identifier.oclc701552618en_US
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