Abstract
Stratigraphic studies of magnetic polarity, paleobotany, and paleoenvironment using Plio-Pleisotocene terrestrial sediments in Japan and north central China were reviewed to investigate climate changes around the Gauss-Matuyama magnetic polarity boundary (GMB). Pollen and plant macrofossil data from Osaka, Aizu, and Tokachi in Japan show an extensive floral change associated with cooling in the latest Gauss chron, which is the largest in scale during the last 3-5 million years. The floral change occurred within a zone just below the GMB, where warmer elements disappeared stepwise and new cooler elements emerged also stepwise. In Tokachi, northern Japan, a long-term warmer climate that began at about 3.7Ma terminated just before the GMB, followed by recovery of a boreal climate. In the Chinese Loess Plateau, the GMB occurs around the loess/red clay boundary (LRB). However, the GMB lies at various depths ranging from 5m to -4m above the LRB, which is too wide to be explained by downward displacements due to delayed acquisition of post-depositional remanent magnetization. Local climates may have originated regional variability in lithology. The strong cooling event predating both the GMB and the LRB is consistent with that observed in Japan. Magnetic susceptibility of the red clay suggests occurrence of a long-term warm-moist climate from 3.4Ma to 2.75Ma, which may be related to that in Tokachi.
