Tilt and rotation of the footwall of a major normal fault system: Paleomagnetism of the Black Mountains, Death Valley extended terrane, California

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5024678

Holm, D K ^[1]; Geissman, J W ^[2]; Wernicke, B ^[3]

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1. Kent State Univ., OH (United States). Dept. of Geology
2. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology and Planetary Sciences
3. California Inst. of Tech., Pasadena, CA (United States). Dept. of Geology and Planetary Sciences

Paleomagnetic data have been obtained from Miocene intrusions, Proterozoic Paleomagnetic data have been obtained from Miocene intrusions, Proterozoic crystalline rocks and cross-cutting mafic to felsic dikes to evaluate footwall deformation during extension and unroofing of the crystalline core of the Black Mountains, Death Valley, California. Synrift intrusions contain a well-defined and, at the site level, well-grouped magnetization, interpreted to be of dual polarity, whose in situ direction is discordant in declination and inclination with an expected late Cenozoic reference direction. In situ site mean directions of this magnetization are directed towards the west and west-northwest with moderate to shallow positive and negative inclinations. The variation in magnetization direction, particularly inclination, with site locality around the turtleback structures along the western flank of the Black Mountains suggests folding of the intrusion after remanence acquisition. Two populations of in situ site means are identified: one with southwest declination and negative inclination, the other with northward declination and positive inclination. A preferred interpretation for footwall deformation involves, from oldest to youngest: (1) northeast-side up tilting of 20--40[degree] and local folding of the crystalline rocks associated with early structures (the Death Valley turtlebacks) between 11.6 and 8.7 Ma, (2) progressive east to west footwall unroofing between 8.7 and [approximately]6.5 Ma, and (3) large-scale clockwise rotation (50--80[degree]) after the core detached from stable terrane to the west. The authors interpret late rotation as oroflexure related to right-lateral shear along the Death Valley fault zone.

• OSTI ID: 5024678
• 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

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
CALIFORNIA
CENOZOIC ERA
DEFORMATION
DEVELOPED COUNTRIES
DIKES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
GEOMETRY
IGNEOUS ROCKS
INCLINED STRATA
MAGNETISM
MATHEMATICS
MIOCENE EPOCH
NORTH AMERICA
ORIENTATION
PALEOMAGNETISM
PLUTONIC ROCKS
ROCKS
TERTIARY PERIOD
USA