Late Cretaceous tectonics of the southern Sierra Nevada batholith (SNB) viewed from the Tehachapi Mountains (TM), California
- California Inst. of Technology, Pasadena, CA (United States). Division of Geological and Planetary Sciences
- Duke Univ., Durham, NC (United States). Dept. of Geology
Integrated geological and geophysical studies shows that the TM expose a unique structural configuration whereby generally intact crystalline rocks of the SNB are tilted up to deep crustal levels, and are tectonically underlain by the Rand Schist (RS). The RS constitutes part of a regional subcreted ensimatic terrane (ET) that underlies much of southern CA. Viewed from the north the TM crystalline rocks are the autochthonous deepest exposed levels of the SNB. Viewed from the south, the crystalline rocks appear to be allochthonous above the north dipping RS along the northern margin of the ET. In the authors' working model the protolith of the ET was thrust at low angle beneath the Mojave and southernmost Sierra segment of the Cordilleran batholithic belt during Late Cretaceous Laramide subduction. The lowermost batholithic crust was delaminated, displaced down the subduction zone, and replaced by the ET. The ET was wet, and upward escaping fluids weakened the overlying quartz-rich batholithic crust. The tectonically thickened crust, collapsed under its own burden with regional horizontal flow in the ET and the partitioning of the upper crust into flat-lying sheets bordered by ductile-brittle shear zones having a complex network of normal and reverse slip patterns and with overall westward transport dominating. The north dip of the Rand thrust beneath the TM may simply reflect the attenuated northern margin of the ET, or alternatively some component of the original dip of the subcretion thrust system. The latter is suggested by the flattening out of the southernmost proto-Kern Canyon fault (PKCF) into structures that appear to be related to the Rand thrust system, as through the dextral PKCF was a lateral ramp in the system. The implied strong dextral oblique motion is consistent with Late Cretaceous plate reconstructions. The effect of this transpressive deformation within the SNB may have been substantial as far north as lat. 38[degree].
- OSTI ID:
- 5128800
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Crustal structure of Ouachita Mountains, Arkansas: A model based on integration of COCORP reflection profiles and regional geophysical data
Mesozoic-Cenozoic paleographic evolution of Northern South America
Related Subjects
CALIFORNIA
GEOLOGIC STRUCTURES
SUBDUCTION ZONES
GEOLOGY
TECTONICS
GEOLOGIC MODELS
CRETACEOUS PERIOD
DEFORMATION
GEOLOGIC FAULTS
GEOLOGIC HISTORY
PETROGENESIS
PLUTONIC ROCKS
SCHISTS
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGIC FRACTURES
IGNEOUS ROCKS
MESOZOIC ERA
METAMORPHIC ROCKS
NORTH AMERICA
PETROLOGY
ROCKS
USA
580000* - Geosciences