Did the San Gabriel Mountains once floor the Los Angeles basin : Evidence from a Late Cenozoic magmatic event
Conference
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· Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5096507
- San Diego State Univ., CA (United States). Dept. of Geological Sciences
- California State Polytechnic Univ., Pomona, CA (United States). Dept. of Geological Sciences
A series of Late Cenozoic dikes intrude the crystalline basement complex of the San Gabriel Mountains. The dikes range in composition from basalt to rhyolite. Rocks of andesite composition are dominant. Cross-cutting relationships consistently show that the less abundant, high-silica units were emplaced during two or more initial pulses of magmatic activity. This was followed by at least four additional pulses of increasingly quartz-poor magma. The nature of the contacts between the dikes and their host suggest that the dikes were emplaced during progressive unroofing of the San Gabriel Mountains basement complex. In the northeastern corner of the Los Angeles basin, units within the Glendora Volcanics (Shelton, 1955) share many compositional and spatial characteristics with the dikes in the San Gabriel Mountains. The dikes may have served as mid-crustal conduits which fed the overlying Glendora Volcanics during widespread magmatism that accompanied the extensional opening of the Los Angeles basin sphenochasm (Luyendyk, 1991; Wright, 1991). The authors believe that the crystalline basement complex now exposed in the San Gabriel Mountains once floored portions of the Los Angeles basin prior to Miocene extension and magmatism. They feel that unroofing was accomplished by low-angle normal faulting during the opening of the Los Angeles basin.
- OSTI ID:
- 5096507
- Report Number(s):
- CONF-9305259--
- Conference Information:
- Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
- Country of Publication:
- United States
- Language:
- English
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Conference
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Wed Mar 31 23:00:00 EST 1993
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OSTI ID:5098700
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Journal Article
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Tue Mar 04 19:00:00 EST 2025
· Geosphere
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OSTI ID:2553126
H. R. 3207: This Act may be cited as the San Gabriel Basin Demonstration Project Act of 1991, introduced in the US House of Representatives, One Hundred Second Congress, First Session, August 2, 1991
Book
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Mon Dec 31 23:00:00 EST 1990
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OSTI ID:6995284