HR: 0800h
AN: T41A-0360    [Abstracts]
TI: New Constraints on plate motions in the Woodlark Basin, Papua New Guinea: Can Euler pole kinematics be used to predict continental extension?
AU: * Goodliffe, A M
EM: amg@ua.edu
AF: Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487,
AU: Taylor, B
EM: taylorb@hawaii.edu
AF: SOEST, University of Hawaii, Honolulu, HI 96822,
AU: Kington, J
EM: joferkington@gmail.com
AF: Dept. of Geology & Geophysics, University of Wisconsin-Madison, Madison, WI 53706,
AB: The Woodlark Basin is one of the only active rift systems in the world where the amount of strain can be predicted through direct observations of brittle extension, subsidence, and motion around a well-constrained Euler pole. Work on rift systems worldwide has shown that in many instances the amount of brittle extension falls well short of the extension predicted by subsidence. A recent interpretation of marine seismic reflection data from the Woodlark basin has shown that at the rifting-to-spreading transition the estimates of extension predicted from subsidence and brittle extension are in close agreement if multiple phases of faulting and sub-resolution faulting are taken into account. However, extension predicted by both methods is approximately a factor of two less than that predicted by Euler pole kinematics. In an attempt to thoroughly catalogue this discrepancy, we re-evaluate the estimate of extension calculated using Euler pole kinematics. Due to a lack of data close to the margins in the eastern half of the basin, previous reconstructions of the basin opening history used two distinct Euler poles and assumed that the earliest was valid back to 6 Ma, the approximate time at which seafloor spreading started in the basin. In 2004 a marine geophysical survey mapped the remainder of the basin, including fracture zone traces from the spreading center to the margins and all identifiable magnetic chrons. Using bootstrap re-sampling constrained by all available data, Euler pole locations and rates were derived for each magnetization chron. The results show that the Euler poles from present to chron 2A are very well constrained. Prior to this time the errors in the location and rate of the Euler poles become far greater. However, there is little reason to believe that the location of the Euler pole changes dramatically. Though the amount of extension predicted using this method still exceeds that predicted through detailed interpretations of the reflection seismic data and estimates of extension predicted by subsidence, potential mechanisms to close this gap include the accommodation of strain by metamorphic core complex emplacement and magmatic arc additions.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting