HR: 1340h
AN: T33C-0558    [Abstracts]
TI: Strain Accommodation Along an Oblique Subduction Zone: Integrating Paleomagnetic Data and Stress Patterns in the Central Aleutian Forearc
AU: * Krutikov, L
EM: ftlk@uaf.edu
AF: University of Alaska Fairbanks, P.O. Box 757220, Fairbanks, AK 99775 United States
AU: Reynolds, J R
EM: jreynolds@guru.uaf.edu
AF: University of Alaska Fairbanks, P.O. Box 757220, Fairbanks, AK 99775 United States
AU: Stone, D B
EM: dstone@gi.alaska.edu
AF: University of Alaska Fairbanks, P.O. Box 757220, Fairbanks, AK 99775 United States
AB: Present day motion of the Pacific plate relative to the North American plate shifts along the Aleutian arc from normal convergence in the east to transform motion in the west. Oblique subduction, partitioned into an arc-normal component and an arc-parallel component, creates a spatially complex pattern of deformation in the overriding plate. Strain partitioning results in tectonic segmentation of the forearc region, caused by increasing obliquity of plate convergence and apparently characterized by clockwise rotation and westward translation of discrete blocks in the central and western Aleutian arc [e.g., Geist et al., Tectonics 7, 327-341, 1988]. Archived cores collected from islands in the central Aleutian arc for previous paleomagnetic studies are being remeasured and reanalyzed using modern thermal demagnetization techniques that were not available at the time of collection. These new measurements indicate counterclockwise rotation or less significant clockwise rotations than those predicted by the block rotation model. Paleomagnetic results are presented for Tertiary and Quaternary volcanic rocks from Adak and Amchitka Islands in the central Aleutians. Results range from no statistically significant rotation in young intrusives, to a number of paleomagnetic vectors in the Finger Bay volcanics (~55 Ma) that suggest clockwise rotation since the time of original magnetization. Paleomagnetic results are combined with analyses of seafloor lineations in high-resolution multibeam sonar data collected in 2003 and 2004 of representative sites between 173W and 179E along the central Aleutian arc. Major fault lineations and joint patterns observed in the bathymetry data are analyzed to estimate the direction of maximum horizontal stress. Lineations in rocks of different stratigraphic ages and paleomagnetic results are being compared with 0-5Ma regional stress patterns [Scholl et al., 1989] to constrain the style and timing of deformation.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 8150 Plate boundary: general (3040)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005