Origin of West Pacific seamounts and features of the cretaceous dynamics of the Pacific plate

A correlation between the age and position of 25 seamounts in the West Pacific Ocean formed, judging from the 40 Ar/ 39 Ar data, in the period from 120 to 65 My B.P. was recognized. The seamounts studied are joined into linear zones with extensions up to 5000 km; the age of the seamounts decreases in the southeastern direction. In the interval 93–83 My B.P., the seamount formation was extremely rapid; this interval coincides with the period of acceleration in the Pacific plate movements. In the middle of this interval, 87 My B.P., an intensification of the magmatic activity accompanying the seamount formation was observed simultaneously with the extinction of the Isanagi plate and the appearance of the Kula plate. The results of this study are in the best agreement with the hypothesis of diffuse tension of the Pacific plate at its displacement in the northwestern direction, which led to the formation of weak zones of decompressional melting. The complementary character of the system of tension zones in the western part of the ocean with respect to the system of major transform faults in its eastern part, which probably reflects the common general process of deformation of the Pacific lithosphere in the Cretaceous, is shown.