HR: 0800h
AN: T41A-1161    [Abstracts]
TI: Plate Kinematic Model and Resulting Evolution of Oceanic Transform Fault Tectonics Adjacent to the Macquarie Triple Junction, SW Pacific
AU: Symons, C M
EM: csymons@ucsd.edu
AF: Geological Data Center, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive Dept 0220 , La Jolla, CA 92093-0220 United States
AU: * Meckel, T A
EM: tmeckel@usgs.gov
AF: Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, 4412 Spicewood Springs Rd. #600, Austin, TX 78759-8500 United States
AU: * Meckel, T A
EM: tmeckel@usgs.gov
AF: Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C1100, Austin, TX 78712-0254 United States
AU: Mosher, S
EM: mosher@mail.utexas.edu
AF: Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 1 University Station C1100, Austin, TX 78712-0254 United States
AU: Coffin, M F
EM: mcoffin@ori.u-tokyo.ac.jp
AF: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639 Japan
AB: This research presents reconstructions illustrating the configuration of the Australian-Pacific-Antarctic plate system and the Macquarie Triple Junction (MTJ) at 7 times from 33.3 Ma to the present (A13o, A8o, A6o, A5o, A3Ay, A2Ay, and 0). Plate kinematic models are used to characterize the style of plate interaction between the three plates as the dominantly Ridge-Transform-Transform triple junction evolved. Models of MTJ evolution presented here focus on the complex crustal interactions that occurred at the southern Australian-Pacific plate boundary during this time, and constrain the tectonic evolution of the obliquely-convergent transform boundary that actively constructs the southern Macquarie Ridge Complex. Surprising results include the apparent shortening of the easternmost Southeast Indian Ridge (SEIR) by ~200 km during the lengthening of the transform due to southern migration of the MTJ. Such behavior explains the curved shape of the transform that evolved into the Hjort Trench and may be one process by which the Hjort region has accommodated convergence during its transition from transform fault to obliquely convergent incipient subduction zone. Differences between the amount of observed subduction at the Puysegur and Hjort Trenches may be a result of the partial accommodation of convergence by shortening of the easternmost SEIR spreading segment adjacent to the Hjort Trench during transform fault evolution. Reconstructions indicate that the Antarctic-Pacific boundary was a transform fault connecting the Antarctic-Pacific spreading ridge system with the SEIR for times between 33.3 and 5.9 Ma. Between 26.6 and 10.9 Ma the Antarctic-Pacific boundary was likely a leaky transform, accommodating some divergence between the two plates. At 5.9 Ma, a change in Antarctic-Pacific relative plate motion caused the transform fault to evolve into a spreading ridge. The spreading since 5.9 Ma served to more efficiently link the SEIR and Antarctic-Pacific spreading ridge systems, as the relative motion of the Antarctic-Pacific and Antarctic-Macquarie plates became similar in direction and magnitude.
DE: 8150 Plate boundary--general (3040)
DE: 8155 Plate motions--general
DE: 8157 Plate motions--past (3040)
DE: 8158 Plate motions--present and recent (3040)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting