Jurassic Cordilleran dike swarm-shear zones: Implications for the Nevadan orogeny and North American plate motion

Journal Article · Sat Aug 01 00:00:00 EDT 1992 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1992)020<0745:JCDSSZ>2.3.CO;2· OSTI ID:6893603

Wolf, M B; Saleeby, J B ^[1]

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1. California Inst. of Technology, Pasadena, CA (United States)

A cogenetic and coeval tonalitic and mafic dike swarm has been identified within a southern fragment (the Owens Mountain area) of the western Foothills terrane (California). The dikes were mylonitized and transposed (rotated into subparallel orientation) during emplacement, from 155 to 148 Ma (U-Pb zircon data), which coincides in time with the Nevadan orogeny. Steeply southeast-plunging fold axes and S-fold geometries indicate a sinistral-sense of shear, possibly with some dip-slip motion as well. This shear zone may be the southern and possibly deeper extension of the Bear Mountains fault zone. This and other Late Jurassic Cordilleran dike swarms record a complex pattern of sinistral-sense transtension-transpression that developed at the apparent-polar-wander J2 cusp ([approximately] 150 Ma) and during subsequent, rapid, northwestward acceleration of North America. The Late Jurassic Nevadan orogeny is a manifestation of these dramatic changes in magnitude and direction of North American motion.

• OSTI ID: 6893603
• Journal Information: Geology; (United States), Vol. 20:8; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
OROGENESIS
GEOLOGIC MODELS
PLATE TECTONICS
SIERRA NEVADA COLORADO
CALIFORNIA
DIKES
GEOLOGIC FAULTS
GEOLOGIC HISTORY
IGNEOUS ROCKS
JURASSIC PERIOD
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
MESOZOIC ERA
MOUNTAINS
NORTH AMERICA
ROCKS
TECTONICS
USA
580000* - Geosciences