Late Cenozoic volcanism, subduction, and extension in the Lassen region of California, Southern Cascade Range
- Geological Survey, Reston, VA (USA)
- Geological Survey, Menlo Park, CA (USA)
The authors identify 537 volcanic vents younger than 7 Ma, and they classify these into five age intervals and five compositional categories based on SiO{sub 2} content. Maps of vents by age and composition illustrate regionally representative volcanic trends. Most mafic volcanism is calcalkaline basalt and basaltic andesite. However, lesser volume of low-potassium olivine tholeiite (LKOT), a geochemically distinctive basalt type found in the northern Basin and Range province, also has erupted throughout the Lassen segment of the Cascade arc since the Pliocene. Normal faults and linear groups of vents are evidence of widespread crustal extension throughout most of the Lassen region. NNW alignments of these features indicate NNW orientation of maximum horizontal stress (ENE extension), which is similar to the stress regime in the adjacent northwestern Basin and Range and northern Sierra Nevada provinces. They interpret the western limit of the zone of NNW trending normal faults as the western boundary of the Basin and Range province where it overlaps the Lassen segment of the Cascade arc. The Lassen volcanic region occurs above the subducting Gorda North plate but also lies within a broad zone of distributed extension that occurs in the North American lithosphere east and southeast of the present Cascadia subduction zone. The scarcity of volcanic rocks older than 7 Ma suggests that a more compressive lithospheric stress regime prior to the late Miocene extensional episode may have suppressed volcanism, even though subduction probably was occurring beneath the Lassen region.
- OSTI ID:
- 5195795
- Journal Information:
- Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B12; ISSN 0148-0227; ISSN JGREA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
AGE ESTIMATION
CALIFORNIA
CENOZOIC ERA
CHALCOGENIDES
CHEMISTRY
CLASSIFICATION
CONTINENTAL CRUST
DEFORMATION
DEVELOPED COUNTRIES
EARTH CRUST
FEDERAL REGION IX
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
LINEAMENTS
NORTH AMERICA
ORIENTATION
OXIDES
OXYGEN COMPOUNDS
QUATERNARY PERIOD
ROCKS
SEDIMENTARY BASINS
SILICON COMPOUNDS
SILICON OXIDES
SUBDUCTION ZONES
TECTONICS
USA
VOLCANIC REGIONS
VOLCANIC ROCKS
VOLCANISM
VOLCANOES