Mechanism for generating the anomalous uplift of oceanic core complexes: Atlantis Bank, southwest Indian Ridge
- A. Graham Baines*2,
- Michael J. Cheadle*2,
- Henry J.B. Dick*3,
- Allegra Hosford Scheirer*4,
- Barbara E. John*5,
- Nick J. Kusznir*6 and
- Takeshi Matsumoto*7
- 2 Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA
- 3Woods Hole Oceanographic Institution, Woods Hole Road, Woods Hole, Massachusetts 02543, USA
- 4U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA
- 5Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA
- 6Department of Earth Sciences, University of Liverpool, Liverpool L69 3BX, UK
- 7Nippon Marine Enterprises, Ltd., 14-1 Ogawacho, Yokosuka 238-0004, Japan
Abstract
Atlantis Bank is an anomalously uplifted oceanic core complex adjacent to the Atlantis II transform, on the southwest Indian Ridge, that rises >3 km above normal seafloor of the same age. Models of flexural uplift due to detachment faulting can account for ∼1 km of this uplift. Postdetachment normal faults have been observed during submersible dives and on swath bathymetry. Two transform-parallel, large-offset (hundreds of meters) normal faults are identified on the eastern flank of Atlantis Bank, with numerous smaller faults (tens of meters) on the western flank. Flexural uplift associated with this transform-parallel normal faulting is consistent with gravity data and can account for the remaining anomalous uplift of Atlantis Bank. Extension normal to the Atlantis II transform may have occurred during a 12 m.y. period of transtension initiated by a 10° change in spreading direction ca. 19.5 Ma. This extension may have produced the 120-km-long transverse ridge of which Atlantis Bank is a part, and is consistent with stress reorientation about a weak transform fault.
Footnotes
-
↵* gbainesuwyo.edu
-
- Accepted August 19, 2003.
- Received May 16, 2003.
- Revision received August 15, 2003.
- Geological Society of America
