Stratigraphic Complexity and Basement Structure in the Western Aleutian Basin of the Bering Sea
Abstract
Multichannel seismic, chirp subbottom and multibeam bathymetric data collected in 2011, in support of the US Extended Continental Shelf project, reveal previously unrecognized complexity in sediment depositional patterns of the western Bering Sea. The region of focus is in the center of the deep-water Aleutian Basin, roughly equidistant from the Shirshov ridge, Bowers ridge and Beringian margin. Sediment thickness ranging between 2 and 4 km completely covers basement topography here, masking rugged basement ridges. There are 2 dominant structural trends in the basement, one oriented N-S, and the other NE-SW ( 38 degrees). In the region of interest, these trends are evidenced in the sedimentary section as well. A prominent boundary in marine magnetic fabric bifurcates the basin between Shirshov and Bowers ridges, oriented NE-SW and roughly on trend with the strike-slip Kobuk fault system of NW Alaska. It separates N-S lineated fabric reminiscent of seafloor spreading (to east) from fabric reminiscent of some extensional margins (to west). The crust across this boundary appears to be entirely oceanic, based on velocity structure. A significant basement trough, a half graben with bounding fault to the west, lies near to the magnetic fabric change. Beginning above this basement graben, the seafloor shallows steadily westward; the basement does not. Our seafloor data show lineated folds or channels, oriented N-S and not running directly downslope, associated with shallow sedimentary horizon disruption reminiscent of shear deformation. This is the only part of the deep-water Aleutian Basin to show any significant seabed topography. This is also the only part of the basin to exhibit tilted (or inclined) stratigraphic sequences, which result in regionally extensive apparent onlap surfaces within the young upper 1.5 km of basin fill. Complex depositional patterns are attributed to competing influences of differential compaction and diagenesis, glacial cycle controls on distant sediment supplies, and possibly basement block adjustments related to loading, regional escape tectonics, or rotation of the Bering plate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.T11C2638B
- Keywords:
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- 1031 Subduction zone processes;
- GEOCHEMISTRYDE: 9355 Pacific Ocean;
- GEOGRAPHIC LOCATIONDE: 3001 Back-arc basin processes;
- MARINE GEOLOGY AND GEOPHYSICSDE: 8104 Continental margins: convergent;
- TECTONOPHYSICS