The last spreading episode of the West Philippine Basin revisited

Serge Lallemand (1) , Stephane Dominguez (1) , Anne Deschamps (1)

1 Laboratoire de Géophysique, Tectonique et Sédimentologie

In 1996, bathymetric data and backscatterlng imagery were gathered along a 20 km-wide NW-SE transect across the West Philippine Basin (WPB), between Taiwan and the Palau-Kyushu Ridge. These data reveal fine-scaled structures of the fossil spreading axis from which we infer episodes of oblique deformation and diminished magmatic supply resulting from cessation of spreading. An original NESW seafloor fabric is observed in the basin northeast of the Benham volcanic plateau. Since this trend is oblique to the more common E-W and NW-SE seafloor fabrics known in the WPB, it could be the result of overlap of two segments of the spreading axis. Several rhomboidal structures exist in the vicinity of the rift valley, suggesting that dextral shear occurred along the central basin rift axis during the last spreading phase. The E-W spreading segments associated with N-S nontransform discontinuities that occur between 127øE and 132øE were probably cross-cut during a final, largely amagmatic, extensional phase to produce a N I30 ø -trending deep rift valley.

Domaines: Géophysique [physics.geo-ph]; Tectonique

Serge Lallemand, Stephane Dominguez, Anne Deschamps. The last spreading episode of the West Philippine Basin revisited. Geophysical Research Letters, 1999, 26 (14), pp.2073-2076. ⟨hal-03407774⟩