Development and Application of Geochronometric Techniques to the Study of Sierra Nevada Uplift and the Dating of Authigenic Sediments

Persistent Link:
http://hdl.handle.net/10150/195423
Title:
Development and Application of Geochronometric Techniques to the Study of Sierra Nevada Uplift and the Dating of Authigenic Sediments
Author:
Cecil, Mary Robinson
Issue Date:
2009
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:
This dissertation contains studies that use various geochronometric and thermochronometric techniques to better understand the post-magmatic evolution of Sierra Nevada, California. (U-Th)/He ages in apatite and zircon from Sierran batholithic rocks are used to constrain the Cenozoic exhumation of the northern part of the range. Zircon and apatite ages determined from the same samples revealed relatively rapid cooling and exhumation rates (0.2 - 0.8 km/My) from ~ 90 to 60 Ma, followed by tectonic quiescence and slow exhumation (0.02 - 0.04 km/My) from the late Paleocene to present. In addition to the thermochronology of basement lithologies, the detrital zircon geochronology of grains from preserved Eocene fluvial sediments in the central and northern Sierra Nevada was performed. U-Pb ages of detrital zircons from the deposits were found to have distributions closely matching age-area estimates of Mesozoic plutons in the Sierra Nevada, suggesting that Eocene river systems were draining local Sierran catchments and likely had steeper axial gradients than has been proposed. Provenance analysis of the Eocene sediments is used to provide constraints on the paleotopography of the Sierra Nevada and inferred range-wide Cenozoic uplift.In addition to the Sierra Nevada work, this dissertation also contains studies that focus on the development of the K-Ca system as a geochronometric technique suitable for dating the deposition of sedimentary sequences. We present a new method for measuring Ca isotopic ratios using a multi-collector ICP-MS equipped with a hexapole collision cell. Isobaric argon interferences are minimized via gas phase reactions in the collision cell. The reproducibility of Ca ratio measurements is found to be ~ 0.02 % (RSD), which is comparable to high precision TIMS techniques and an order of magnitude improvement over single collector ICP-MS techniques using a similar reaction cell method. K-Ca ages of glauconite and K-rich evaporites are determined in order to evaluate the usefulness of the K-Ca system as a sedimentary geochronometer. K-Ca ages in both glauconite and K-salts are found to be variable and significantly younger than documented depositional ages. Reported ages, however, are thought to be recording important basinal thermal histories and recrystallization events.
Type:
text; Electronic Dissertation
Keywords:
Geochronology; K-Ca; Sierra Nevada; Uplift
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Ducea, Mihai

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleDevelopment and Application of Geochronometric Techniques to the Study of Sierra Nevada Uplift and the Dating of Authigenic Sedimentsen_US
dc.creatorCecil, Mary Robinsonen_US
dc.contributor.authorCecil, Mary Robinsonen_US
dc.date.issued2009en_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.abstractThis dissertation contains studies that use various geochronometric and thermochronometric techniques to better understand the post-magmatic evolution of Sierra Nevada, California. (U-Th)/He ages in apatite and zircon from Sierran batholithic rocks are used to constrain the Cenozoic exhumation of the northern part of the range. Zircon and apatite ages determined from the same samples revealed relatively rapid cooling and exhumation rates (0.2 - 0.8 km/My) from ~ 90 to 60 Ma, followed by tectonic quiescence and slow exhumation (0.02 - 0.04 km/My) from the late Paleocene to present. In addition to the thermochronology of basement lithologies, the detrital zircon geochronology of grains from preserved Eocene fluvial sediments in the central and northern Sierra Nevada was performed. U-Pb ages of detrital zircons from the deposits were found to have distributions closely matching age-area estimates of Mesozoic plutons in the Sierra Nevada, suggesting that Eocene river systems were draining local Sierran catchments and likely had steeper axial gradients than has been proposed. Provenance analysis of the Eocene sediments is used to provide constraints on the paleotopography of the Sierra Nevada and inferred range-wide Cenozoic uplift.In addition to the Sierra Nevada work, this dissertation also contains studies that focus on the development of the K-Ca system as a geochronometric technique suitable for dating the deposition of sedimentary sequences. We present a new method for measuring Ca isotopic ratios using a multi-collector ICP-MS equipped with a hexapole collision cell. Isobaric argon interferences are minimized via gas phase reactions in the collision cell. The reproducibility of Ca ratio measurements is found to be ~ 0.02 % (RSD), which is comparable to high precision TIMS techniques and an order of magnitude improvement over single collector ICP-MS techniques using a similar reaction cell method. K-Ca ages of glauconite and K-rich evaporites are determined in order to evaluate the usefulness of the K-Ca system as a sedimentary geochronometer. K-Ca ages in both glauconite and K-salts are found to be variable and significantly younger than documented depositional ages. Reported ages, however, are thought to be recording important basinal thermal histories and recrystallization events.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectGeochronologyen_US
dc.subjectK-Caen_US
dc.subjectSierra Nevadaen_US
dc.subjectUpliften_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.chairDucea, Mihaien_US
dc.contributor.committeememberDucea, Mihaien_US
dc.contributor.committeememberChase, Clemen_US
dc.contributor.committeememberPatchett, Jonathanen_US
dc.contributor.committeememberZandt, Georgeen_US
dc.contributor.committeememberKapp, Paulen_US
dc.identifier.proquest10406en_US
dc.identifier.oclc659752031en_US
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