Late Cenozoic geology of Cajon Pass: implications for tectonics and sedimentation along the San Andreas fault

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:6827634

Weldon, II, R J

The geology in Cajon Pass, southern California, provides a detailed history of strike-slip activity on the San Andreas fault, compressional deformation associated with the uplift of the central Transverse Ranges and an excellent Cenozoic record of syntectonic sedimentation. Age control was established in all of the sediments deposited since the Early Miocene, using biostratigraphy, magnetostratigraphy, fission-track dating of volcanic ashes, radiocarbon dating, soil development, and the relative stratigraphic and geomorphic position of the units. Detailed mapping revealed that tectonic deformation and sedimentation styles varied through time, reflecting the evolution of the San Andreas fault zone within the Pacific-North American plate boundary and climatic changes. Three distinct phases of the uplift of the San Bernardino Mountains have been recognized, suggesting a long-term interaction between the strike-slip activity on the San Andreas system and the compressional tectonics of the Transverse Ranges. Uplift began in the late Miocene, paused during the Pliocene, recommenced in the earliest Pleistocene and culminated in the late Pleistocene. The average slip rate across the combined San Andreas and San Jacinto faults was 37.5 +/- 2 mm/yr during the Quaternary Period. The Holocene slip rate on the San Andreas fault in Cajon Pass was determined to be 24.5 +/- 3.5 mm/yr. This investigation indicates that the last earthquake associated wit rupture on the San Andreas fault in Cajon Pass occurred around 1700 AD and that the average recurrence interval between earthquakes is between 150 and 200 years. A kinematic model was constructed from the structural and slip rate data developed here that produces internally consistent motions for all of the fault-bounded blocks in southern California.

• Research Organization: California Inst. of Tech., Pasadena (USA)
• OSTI ID: 6827634
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
AGE ESTIMATION
CALIFORNIA
CENOZOIC ERA
EARTHQUAKES
FEDERAL REGION IX
FORECASTING
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
ISOTOPE DATING
MAPPING
MOUNTAINS
NORTH AMERICA
SAN BERNARDINO MOUNTAINS
SEDIMENTATION
SEISMIC EVENTS
STRATIGRAPHY
TECTONICS
USA