Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.t21d1862w&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #T21D-1862
Physics
[8000] Structural Geology, [8100] Tectonophysics
Scientific paper
During mapping (by the Undergraduate Team Research program, University of Southern California) in the Saddlebag Lake pendant just along the eastern margin of the Tuolumne batholith we have discovered a brittle slip component in the ESCSZ that juxtaposes largely metasedimentary and metavolcanic rock packages. The metasedimentary package is dominated by bedded sandstones and siltstones and local conglomerates whereas the metavolcanics show a large range of volcanic and volcaniclastic units. All of the units dip steeply and have an average N-NW strike. Dextral oblique ductile shear is distributed in domains in both rock packages with varying width from ~2 km in the South to ~1 km in the North. Shear sense in planes at high angles to a steep to SW plunging mineral lineation include S-C structures, shear bands, asymmetrical folding, sigma and delta clasts, and asymmetrical boudins. Partitioning of shear is common with the metarhyolites and metasediments showing higher non-coaxial strain than in the metaandesite and metadacite units. Map-scale “z-shaped” asymmetrical folds within the shear zone are also consistent with dextral shearing. Folded and sheared dikes of the 88-85 Ma Cathedral Peak phase of the Tuolumne batholith are common in the shear zone. A newly discovered brittle slip surface with breccias, gouge, and local pseudotachylite and large quartz veins was also mapped in the center of the ductile shear zone typically along the contact between the western metasedimentary and eastern metavolcanics (often a metarhyolite at the contact) on the east. Local slickenlines, steps, and offset dikes indicate that the brittle fault also had oblique dextral movement, similar to the ductile shear zone. In the mapped area no dikes originating from the TB cross the brittle fault and some are terminated at the brittle fault surface We interpret these observations to indicate northward displacement of the metasedimentary package by first ductile then brittle faulting during cooling and possibly uplift of this region with the youngest motion post 82 Ma.
Cao Weiqun
Culbert K. N.
Ehret P.
Enriquez M.
Gross M. B.
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A LATE BRITTLE COMPONENT OF MOTION WITHIN THE DUCTILE EASTERN SIERRA CREST SHEAR ZONE (ESCSZ) ALONG THE EASTERN BOUNDARY OF THE TOLUMNE BATHOLITH IN THE SADDLEBAG LAKE, CA AREA. WHITESIDES, Andrew1, ENRIQUEZ, Marcus2 , HARDY, Jill1 , EHRET, Philip1, IANNON does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
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