Drilling Strategy | Table of Contents
Proposed Site
Site WP-1B
Proposed Site WP-1B is situated on flat seafloor at a water depth of 5640 meters below sea level
(mbsl) ~100 km west of the Kyushu-Palau Ridge axis along the eastern edge of the west
Philippine Basin. The site lies on Chron 21, suggesting a basement age of 49 Ma. The sediment
section is predicted to be ~400 to 450 m thick based on recent seismic reflection surveys showing
a two-way traveltime to basement of 0.5 s. Drilling at other sites in the region on Legs 31 and 59
(Karig et al., 1975; Kroenke et al., 1980) recovered a relatively barren, deep-water section
dominated by Holocene to Eocene/Paleocene(?) brown pelagic silty clays overlying basement near
the Oki-Daito Ridge (DSDP Sites 294/295). At DSDP Sites 290 and 447 to the south, the section
consists of a barren interval of Pliocene clays underlaid with Oligocene nannofossil-bearing silty
clays mixed with ash. This was underlain by a thick section of polymict and volcanic breccias
presumably derived from the Kyushu-Palau Ridge. Overlying basement consists of 80% basalt
pillows and 20% dolerite. Because Site WP-1B lies in a similar setting at the foot of the Kyushu
Palau Ridge, it is likely that the section at the proposed site will be similar to that at Sites 290 and
497.
Drilling Strategy | Table of Contents