HR: 1340h
AN: T13B-1355    [Abstracts]
TI: Morphology and Tectonic Evolution of Endeavor Deep
AU: * Pockalny, R A
EM: robp@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Box 200 S. Ferry Rd., Narragansett, RI 02882 United States
AU: Larson, R L
EM: rlar@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Box 200 S. Ferry Rd., Narragansett, RI 02882 United States
AU: Popham, C T
EM: pophamc@gso.uri.edu
AF: Graduate School of Oceanography, University of Rhode Island, Box 200 S. Ferry Rd., Narragansett, RI 02882 United States
AU: Natland, J H
EM: jnatland@msn.com
AF: Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149 United States
AU: Abrams, L J
EM: abramsl@uncw.edu
AF: Center for Marine Science, University of North Carolina at Wilmington, 5600 Marvin K. Moss Lane, Wilmington, NC 28409
AU: Sonder, L J
EM: leslie.sonder@dartmouth.edu
AF: Department of Earth Sciences, Dartmouth College, 6105 Fairchild Hall, Hanover, NH 03755 United States
AB: Endeavor Deep is located on the Nazca/Juan Fernandez plate boundary near the triple junction of the Pacific, Nazca and Antarctic plates. The deep is the tip of the northward propagating East Ridge, which defines the eastern side of the microplate and is presently exposing ~3 Myr old oceanic crust created at the ultra-fast spreading (~150 km/myr) East Pacific Rise. Recently collected high-resolution EM300 bathymetry, deep-tow DSL120 sidescan, surface-towed magnetics, and near-bottom JASON II observations provide important details about the tectonic character and origin of Endeavor Deep. These data define a 70 km-long, 40 km-wide, and 3 km-deep rift which shoals and narrows toward the rift tip to the NW and is deeper and wider away from the rift tip toward the SE. The southern wall of the rift is uplifted and has a characteristic flexural profile. The northern wall is also uplifted, however, the classic flexural profile is complicated by the presence of a large EW-trending massif, which appears to be a rift-truncated compressional ridge emplaced during a phase of NS-oriented compression. Along both rift walls, a series of terraces suggest a series of down-dropped blocks associated with ongoing extension. Along the rift floor, a relatively flat, featureless bottom in the NW evolves into hummocky terrane in the central part of the basin that is characterized by volcanic features reminiscent of 1-2 km diameter pancakes in plan-view. Farther to the SE, tectonic lineations and pillow ridges oriented parallel to the trend of the rift valley dominate the basin floor. Magnetic profiles across this portion of the survey area indicate a well-formed central magnetic anomaly with a width equivalent to a spreading rate of 20 km/Myr, which is predicted by tectonic reconstructions of the plate boundary. Overall, these observations define a four-phase evolution of Endeavor Deep: 1) initial crustal formation at the ultra-fast spreading East Pacific Rise ~3 Ma, 2) regional compression and thrust faulting associated a shear couple along the Nazca/Juan Fernandez plate boundary ~1-3 Ma, 3) initial amagmatic rifting that began about 1 Ma, and 4) initial volcanism evolving to super slow seafloor spreading that began prior to 0.78 Ma.
DE: 9355 Pacific Ocean
DE: 8000 STRUCTURAL GEOLOGY (New field, replaces single entry 8165)
DE: 8158 Plate motions--present and recent (3040)
DE: 3045 Seafloor morphology and bottom photography
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting