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" Styles of deformation in zones of oblique convergence: "
A. B. Damte
A. G. Sylvester
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Latin Dissertation
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English
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| Record Number
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1112987
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TLpq304360890
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| Main Entry
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A. B. Damte
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A. G. Sylvester
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| Title & Author
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Styles of deformation in zones of oblique convergence:\ A. B. DamteA. G. Sylvester
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| College
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University of California, Santa Barbara
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| Date
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1997
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| student score
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1997
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| Degree
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Ph.D.
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| Page No
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176
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| Abstract
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The Mecca Hills area, located along the Coachella Valley segment of the San Andreas fault was characterized by a period of basin formation and sediment accumulation between 2.3 Ma and 0.8 Ma. Transpression and basin inversion in the last 700 ka, which resulted from an 8 angular difference between the orientation of the Mecca Hills segment of the San Andreas fault and the Pacific-North American plate motion vector, is accommodated by two end member and contrasting styles of deformation. The Mecca anticline, Mecca syncline, and numerous small scale folds along the Painted Canyon and San Andreas faults, in the Painted Canyon domain, are on average oriented 30 counter-clockwise from the San Andreas fault, typical of distributed style of deformation. On the other hand, the Skeleton Canyon syncline, Chuckawalla syncline and Skeleton Canyon reverse/thrust fault, in Skeleton Canyon domain, have formed parallel to the San Andreas fault, in partitioned style of deformation. Gravity modeling in the Mecca Hills area shows that the morphology of the basement surface follows large scale structures in the overlying sedimentary units, indicating that part of the basement and the overlying sedimentary unit deformed as one. However, it is postulated that no more than the upper 3-4 km of the basement has been shortened during transpression based on a volume balance calculation in laterally confined deformation. In the absence of shallow level detachment, basement involved deformation in the Painted Canyon domain is accommodated by distributed style of deformation. The intensely deformed, silt-dominated Box Canyon sub-member of the upper Palm Spring Formation provides the mechanically weak layer that is required to partition oblique strain into its respective components in the Skeleton Canyon domain. Therefore, local anisotropy, expressed as mechanical layering between competent and incompetent units, has been found to be sufficient to produce contrasting styles of deformation in transpression, playing a far more important role than previously considered.
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California
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Earth sciences
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Geology
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Geophysics
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gravity modelling
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San Andreas fault
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