Abstract

We revealed terrestrial vegetation and climate patterns during the dark layer depositions in the Japan Sea, which probably reflect millennial-scale East Asian Monsoon fluctuations, based on a new pollen record from the KR07-12 PC-07 core in the southern central part of the Japan Sea. Total pollen concentrations in dark layers show relatively high amounts. Conversely, concentrations in light layers are quite low and likely influenced by changes in transportation and deposition processes associated with atmospheric or oceanic conditions. The fossil pollen assemblages in dark layers of the PC-07 core show similar patterns to those of the terrestrial pollen record from Lake Biwa, whereas pollen depositions from northeastern Asia were likely higher during the glacial periods. Japanese vegetation is likely the primary pollen source at the PC-07 site, especially within dark layers during MIS 5 and 3, because the dominant pollen taxa in the core are Japanese cedar and Japanese beech, which are endemic tree species. We recognize two types of pollen compositions in dark layers of the PC-07 core during MIS 5 and 3: Cryptomeria-dominant dark layers (Cry-DL) and temperate deciduous broadleaf-dominant dark layers (TDB-DL). The pollen record from the PC-07 core suggests that the regional climate conditions in western Japan were wet with a low seasonal contrast within Cry-DL during periods of smaller summer insolation and, in contrast, a relatively dry summer and dry winter within TDB-DL during periods of larger summer insolation.