Spreading cycles in the Pacific Ocean

Changes in the spreading rates in the Pharallon-Pacific-Izanagi (Kula) triple junction during the Cretaceous and Cenozoic are revised using new data of the dynamics of the Pacific plate. The cyclic character of the spreading is recognized, and the stages of its acceleration and deceleration are distinguished. Approximately 130, 87, and 42 My B.P., at the culminations of the cycles, when maximal spreading rates were reached, the principal rearrangements in the tectonic evolution of the ocean occurred. The spreading rates were minimal about 140, 120, 65, and 15 My B.P. The latter periods are marked by pulses of basalt magmatism in the west, east, and northeast of the Pacific Ocean. The study recognized no signs of the intrusion of the Middle Cretaceous superplume, which was suggested by Larson. Both the cycling revealed and the pulsations of the intraplate volcanism are most probably related to the regularities of the deformations of the oceanic lithosphere and reflect the periodic alternations of regimes of compression and extension of the Pacific plate during the last 180 My.