Sedimentation rates in the western Philippine Sea have been determined on three piston cores using the excess ²³⁰Th method. In the deep basin, the sedimentation rates as determined from two cores are 5.3 and 6.8 mm ka^-1 at least for the past 70,000 years. Immediately before that time, a disturbed zone which is recognized at one station appears to have coincided with the onset of the last glaciation. Dating back further, the data suggest a higher sedimentation rate of 17.4 mm ka^-1. However, the data are by no means unambiguous; another interpretation suggests a slower rate (10.6 mm ka^-1) between yet another disturbed zone at greater depth and the one just metioned.

In the southwestern end of the Ryukyu Trench, the excess ²³⁰Th activities are too low to allow a meaningful treatment with this method. The sedimentation rate is expected to be high due to the geologic environment of the trench. A value of about 13 mm ka^-1 with a large uncertainty is obtained when the method is attempted. These sedimentation rates are quite consistent with those obtained in the Philippine Sea by earlier workers.