skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Tectonic implications of space-time patterns of Cenozoic volcanism in the Palo Verde Mountain volcanic field, southeastern California

Abstract

Variations in Cenozoic volcanism in the western United States are believed to correlate closely with changes in tectonic setting. A transition in volcanic association from calc-alkaline to fundamentally basaltic volcanism and subsequent crustal extension, appears to have coincided temporally with the initial collision of the East Pacific Rise with the continental margin trench off western North America, between 28 and 25 Ma. The volcanic stratigraphy of the Palo Verde Mountain volcanic field is broadly similar to other volcanic centers in southeastern California and can be divided into tripartite regional stratigraphy. A basal sequence of andesitic to rhyolitic lava flows, plugs, domes, and extensive pyroclastic deposits rests unconformably on pre-Cenozoic basement rocks. The basal sequence is intruded by cogenetic Cenozoic plutonic rocks and overlain by basaltic to rhyolitic lava flows, dikes, and a second widespread assemblage of pyroclastic deposits, cumulatively referred to as the silicic sequence. The youngest volcanic rocks of the field include olivine basalt flows and breccia which occur at scattered localities in the Palo Verde Mountains. The age, stratigraphy, and chemistry of the intermediate and basaltic composition volcanic rocks broadly supports previously cited volcanic-tectonic models, if modified to incorporate modern plate reconstruction theory. This modification results in amore » southeast migration of the transition to basaltic volcanism to southeastern California occurring significantly later in time than the previously cited ages of transition. Moreover, this southeast migration of the volcanic transition is coincident with the inception of Basin and Range faulting and the initiation of movement on the San Andreas fault south of the Transverse Ranges, corresponding to the southward migration of the Pacific-Cocos Ridge.« less

Authors:
Publication Date:
OSTI Identifier:
5424519
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: Thesis (Ph. D.)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CALIFORNIA; PLATE TECTONICS; CENOZOIC ERA; STRATIGRAPHY; VOLCANISM; FEDERAL REGION IX; GEOLOGIC AGES; GEOLOGY; NORTH AMERICA; TECTONICS; USA 580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)

Citation Formats

Murray, K.S. Tectonic implications of space-time patterns of Cenozoic volcanism in the Palo Verde Mountain volcanic field, southeastern California. United States: N. p., 1981. Web.
Murray, K.S. Tectonic implications of space-time patterns of Cenozoic volcanism in the Palo Verde Mountain volcanic field, southeastern California. United States.
Murray, K.S. 1981. "Tectonic implications of space-time patterns of Cenozoic volcanism in the Palo Verde Mountain volcanic field, southeastern California". United States. doi:.
@article{osti_5424519,
title = {Tectonic implications of space-time patterns of Cenozoic volcanism in the Palo Verde Mountain volcanic field, southeastern California},
author = {Murray, K.S.},
abstractNote = {Variations in Cenozoic volcanism in the western United States are believed to correlate closely with changes in tectonic setting. A transition in volcanic association from calc-alkaline to fundamentally basaltic volcanism and subsequent crustal extension, appears to have coincided temporally with the initial collision of the East Pacific Rise with the continental margin trench off western North America, between 28 and 25 Ma. The volcanic stratigraphy of the Palo Verde Mountain volcanic field is broadly similar to other volcanic centers in southeastern California and can be divided into tripartite regional stratigraphy. A basal sequence of andesitic to rhyolitic lava flows, plugs, domes, and extensive pyroclastic deposits rests unconformably on pre-Cenozoic basement rocks. The basal sequence is intruded by cogenetic Cenozoic plutonic rocks and overlain by basaltic to rhyolitic lava flows, dikes, and a second widespread assemblage of pyroclastic deposits, cumulatively referred to as the silicic sequence. The youngest volcanic rocks of the field include olivine basalt flows and breccia which occur at scattered localities in the Palo Verde Mountains. The age, stratigraphy, and chemistry of the intermediate and basaltic composition volcanic rocks broadly supports previously cited volcanic-tectonic models, if modified to incorporate modern plate reconstruction theory. This modification results in a southeast migration of the transition to basaltic volcanism to southeastern California occurring significantly later in time than the previously cited ages of transition. Moreover, this southeast migration of the volcanic transition is coincident with the inception of Basin and Range faulting and the initiation of movement on the San Andreas fault south of the Transverse Ranges, corresponding to the southward migration of the Pacific-Cocos Ridge.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1981,
month = 1
}

Thesis/Dissertation:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this thesis or dissertation.

Save / Share:
  • Detailed mapping, newly obtained U/Pb age analyses, and finite strain studies completed on a deformed volcanic roof pendant within the eastern Sierra indicate that: (1) little or no penetrative deformation affected the area during the Late Jurassic, and (2) the penetrative structure postdates the Nevadan orogeny by approximately 50 million years. The pendant consists of two volcanic sequences: a steeply dipping, homoclinal series of felsic ash flows and intermediate flows of Mid- to Late Jurassic age and an unconformably overlying series of felsic ash flows and mafic tuffs of Late Cretaceous age. Both sequences possess a single, well-developed, subvertical foliationmore » that trends NNW. Quantitative strain analyses indicate that both the Jurassic and Cretaceous volcanic sequences underwent identical compressional strains of 30-40% shortening. This observation precludes the possibility that significant ductile deformation accompanied the rotation of the Jurassic volcanic rocks and suggests that the penetrative fabric developed within both units is Late Cretaceous in age. Isotopic age determinations on adjacent undeformed or only weakly deformed granitic plutons further indicate that the peak of deformation occurred prior to 102 Ma. Structural considerations and arguments based on the orientation of dikes of the Independence suite suggest that rotation of the Jurassic volcanic sequence took place prior to 148 Ma. in an extensional regime rather than during a Nevadan compressional event as generally interpreted.« less
  • The 5.1 M/sub L/ Santa Barbara earthquake of 13 August 1978 was located 3 km southeast of Santa Barbara at a focal depth of 12.7 km. The temporal-spatial development of the aftershock zone may indicate that the initial rupture plane was considerably smaller than that of the eventual aftershock zone. The aftershock hypocenters outline a nearly horizontal plane (dipping 15/sup 0/ or less) at 13-km depth and the preferred focal mechanism indicates north-over-south thrusting. To further test the decollement hypothesis, Caltech catalog locations were reviewed to determine the depth distribution of earthquakes in the Transverse Ranges. The seismogenic zone ismore » thickest along the southern front of the Transverse Ranges and is thinnest in the southern Mojave Desert and at the east end of the Transverse Ranges. The seismicity of the western Transverse Ranges is typified by north-dipping planar structures and the eastern Transverse Ranges are typified by pervasive seismicity extending down to the floor of the seismogenic zone. Data from a large quarry explosion on Catalina Island were utilized to derive a 3-layer Continental Borderland velocity structure to improve the locations of the 1981 Santa Barbara Island earthquakes. The Santa Barbara Island earthquake (5.3 M/sub L/) occurred on September 4, 1981. Aftershocks exhibited a clear northwest-southeast alignment that coincides with the submarine escarpment of the Santa Cruz-Catalina fault and was consistent with focal mechanisms.« less
  • Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluoritemore » mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system.« less
  • This thesis evaluates rubidium-strontium and samarium-neodymium isotopic and trace element data for a suite of petrologically diverse continental volcanics from the northern Rio Grande rift of the southwestern US and assesses the role of crustal contamination in generating the observed geochemical variations. Covariations of strontium and neodymium isotopic compositions with rock type suggest the operation of crustal contamination. However, the compositional patterns are too complex to support a simple binary mixing model. Some trace element variations suggest that fractional crystallization has been a significant process in the generation of the sample suite. The preferred, but not unique, model to accountmore » for the chemical variations requires contamination of an oceanic-type mantle melt by a partial melt of relatively mafic lower crust. The implications of this analysis for the composition of subcontinental mantle on a regional scale are discussed in light of isotopic studies, both local and global, of other continental volcanics; it is suggested that continental volcanics erupted through thick crust may seldom arrive uncontaminated at the earth's surface. Consequently, subcontinental mantle may be considerably more and less radiogenic in neodymium and strontium, respectively, than the isotopic ratios of continental basalts have led the authors to believe.« less