Abstract
(1) In the field of paleoceanography, there exists ongoing discussion regarding how to investigate past changes in ocean systems. Micropaleontology has contributed to the field of geology via investigations of stratigraphy, paleoenvironments, and paleoclimate, and biology-based investigations of microfossils have led to the establishment of the field of evolutionary micropaleontology. (2) Based on recent investigations, we discuss the timing of the beginning of the Quaternary, the timing of the initiation of 100-kyr cyclicity of glacial-interglacial periods and their cause, the timing of rapid warming that occurs when a glacial period changes to an interglacial (i.e., termination), and the timing of Termination II at the beginning of the last interglacial. (3) Cyclic environmental change over the past 150,000 years is inferred from the diatom assemblages in six piston cores from the Tohoku Area and two piston cores from the Japan Sea. The periodic changes recognized in the Tohoku Area are similar to cyclic changes indicated by various proxies in the Northern Hemisphere.
