In this study the presence of pulse in formation of marginal basins through calculation of production rates based on the age of 22 marginal basins distributed in the western Pacific is revealed. The peaks of their productions appear approximately at 0 Ma, 30 Ma and 60 Ma, with the interval of about 30 my. Production peak appears to be the largest near 30 Ma (45 × 10⁴ ㎢). From the fluctuation of production rates, continuous production of marginal basins after 0 Ma (present-day) is inferred, and it is very likely that a production peak which is considerably higher than 30 Ma peak would appear in the future. Such upward inclination of production rates of marginal basins is vividly contrasting to downward decline of those of normal oceans. During the period of declining activities between 10 Ma and 15 Ma no activities of marginal basins are observed. When the marginal basins are classified into back-arc and non back-arc basins on the basis of their evolutionary processes, it is observed that back-arc basins appear to have cyclic production peaks approximately at 0 Ma, 20 Ma and 45 Ma, with the interval of about 20 my. The present-day back-arc basins appear to he most active in their productions. The phenomenon of fluctuations in the quantity of production upto now shows a upward climbing trend. The periods with less activity of back-arc basins appear to have been active in arc volcanism. It is considered that the formation of marginal basins and arc volcanism have been alternately active with time. Non back-arc basins seem to have been formed concentrically at about 25 Ma - 35 Ma and 55 Ma - 80 Ma. In the back-arc basins distributed near northwestern (NW) and southwestern (SW) Pacific around equator, it is revealed that production peak has been moved from SW (55 - 80 Ma) through NW (15 - 55 Ma) to SW (0 - 10 Ma) Pacific in time and space. It is supposed that the periodic formation of marginal basins with time is associated with spatial cycles.

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