Pollen Assemblages of the Last Glacial Maximum in Okinawa Trough and Their Implication on Paleoenvironment

The high rate sedimentation in the west Okinawa Trough provides good materials for high resolution study on palaeoenvironment evolution. In comparing with SPECMAP curve, the core DGKS-9602 was dated OIS 3 to OIS 1 for a total length of 931 cm. Pollen analysis shows that Pinus was predominated during the OIS 1 and OIS 3 with an average percentage 65%, but it decreased at OIS 2, giving place to the herbs which attained more than 50% in average. This result suggests that the alternation of Pinus/herbs indicates the sea level changes and its variation is comparable with oxygen isotopic curve. The vegetation covered on the continental shelf during the LGM was mainly grassland. Most of sediment origin of the study core might be resulted from the erosion of the continental shelf of the East China Sea, that was characterized by the decrease of components from upriver and mountains in the pollen assemblages. In the light of dust pollen distribution pattern in eastern China, the ratio of Artemisia/Poaceae from the surface samples of the East China Sea can be evaluated to the corresponding latitude in the continent that coincided with middle and lower reach of Changjiang River. Whereas, the ratio obtained from the LGM in the core 9602 has an estimative result of 7 latitudes higher than the surface data, which indicates that the vegetation zones shifted southwards with amplitude comparable with previous studies.