HR: 0800h
AN: T41A-0361    [Abstracts]
TI: Thinning Factors and Crustal Thicknesses at the Propagating Tip of Sea-floor Spreading in the Woodlark Basin
AU: * Gozzard, S P
EM: S.Gozzard@liverpool.ac.uk
AF: University of Liverpool, Department of Earth and Ocean Sciences, Liverpool, L69 3GP, United Kingdom
AU: Kusznir, N
EM: N.Kusznir@liverpool.ac.uk
AF: University of Liverpool, Department of Earth and Ocean Sciences, Liverpool, L69 3GP, United Kingdom
AU: Goodliffe, A
EM: amg@ue.edu
AF: University of Alabama, Department of Geological Sciences, Tuscaloosa, AL 35487, United States
AU: Manatschal, G
EM: manatschal@illite.u-strasbg.fr
AF: University of Strasbourg Louis Pasteur, Institut de Physique du Globe de Strasbourg/Centre de Géochimie de la Surface, Ecole et Observatoire des Sciences de la Terre, Strasbourg, 67084, France
AB: Understanding how the continental crust and lithosphere thins at the propagating tip of sea-floor spreading is the key to understanding the continental breakup process. The Woodlark Basin, a young ocean basin located in the Western Pacific to the east of Papua New Guinea, commenced formation at approximately 8.4Ma and is propagating westwards at a rate of approximately 140km/Myr. Immediately to the west of the most recent segment of sea-floor spreading propagation, in the vicinity of the Moresby Seamount, evidence from bathymetry, subsidence and seismic Moho depth suggests that continental lithosphere is being thinned. In this study we have determined lithosphere thinning in the vicinity of the Moresby Seamount at the level of the whole lithosphere, the whole crust and the upper crust. Whole lithosphere thinning factors have been determined from subsidence analysis; whole continental crustal thinning factors have been determined from gravity inversions and upper crustal thinning factors have been determined from fault analysis. Three 2D seismic profiles surrounding the Moresby Seamount have been flexurally backstripped to the base of the syn-rift sediments to determine the water loaded subsidence. Using the McKenzie lithosphere extension model, modified to include volcanic addition at high thinning factors, whole thinning factors for the lithosphere have been determined from the water loaded subsidence. Results show that thermal subsidence alone cannot account for the observed subsidence, and that an additional initial subsidence is needed. Whole lithosphere thinning factors increase from an average of 0.5 to 0.8 across the Moresby Seamount eastwards towards the propagating tip. A satellite gravity inversion incorporating a lithosphere thermal gravity anomaly correction has been used to determine Moho depth, crustal thickness and thinning factors for the propagating tip in the Woodlark Basin. Moho depths are consistent with depths obtained from receiver function analysis (Ferris et al. 2006). Crustal thickness estimates do not include a correction for sediment thickness and are upper bounds. Crustal thinning factors in the vicinity of the Moresby Seamount are similar to those observed for the whole lithosphere. Fault analysis of the three 2D profiles have been used to determine upper crustal thinning factors. Upper crustal thinning factors between 0.1 to 0.2 are observed for the vicinity of the Moresby Seamount, substantially lower than thinning factors predicted for the whole lithosphere and continental crust, suggesting depth-dependent lithosphere thinning. Crustal thicknesses predicted from gravity inversion immediately to the east of the Moresby Seamount are substantially greater than would be expected for oceanic lithosphere in this region, while highly thinned, has not completely ruptured.
DE: 8104 Continental margins: convergent
DE: 8109 Continental tectonics: extensional (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting