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Density structure of the lithosphere in the southwestern United States and its tectonic significance

Journal of Geophysical Research B: Solid Earth

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Abstract

We calculate a density model of the lithosphere of the southwestern United States through an integrated analysis of gravity, seismic refraction, drill hole, and geological data. Deviations from the average upper mantle density are as much as ?? 3%. A comparison with tomographic images of seismic velocities indicates that a substantial part (>50%) of these density variations is due to changes in composition rather than temperature. Pronounced mass deficits are found in the upper mantle under the Basin and Range Province and the northern part of the California Coast Ranges and adjacent ocean. The density structure of the northern and central/southern Sierra Nevada is remarkably different. The central/southern part is anomalous and is characterized by a relatively light crust underlain by a higher-density upper mantle that may be associated with a cold, stalled subducted plate. High densities are also determined within the uppermost mantle beneath the central Transverse Ranges and adjoining continental slope. The average density of the crystalline crust under the Great Valley and western Sierra Nevada is estimated to be up to 200 kg m~3 higher than the regional average, consistent with tectonic models for the obduction of oceanic crust and uppermost mantle in this region.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Density structure of the lithosphere in the southwestern United States and its tectonic significance
Series title:
Journal of Geophysical Research B: Solid Earth
Volume
106
Issue:
B1
Year Published:
2001
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research B: Solid Earth
First page:
721
Last page:
739