The last spreading episode of the West Philippine Basin revisited
Résumé
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.
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