冲绳海槽末次盛冰期孢粉组合的古环境指示意义

冲绳海槽西陆坡末次冰期的高沉积速率为高分辨率研究提供了良好的材料，DGKS-9602钻孔通过氧同位素年代对比，总长931cm的岩心保存了相当于氧同位素阶段1～3的沉积记录．孢粉分析的结果表明，OIS1和OIS三阶段松属花粉含量占优势，平均含量达65％以上，而OIS2阶段松属百分含量明显降低，草本植物花粉含量增加，超过50％．松属与蒿属等草本花粉间的相互消长指示了海平面的升降，并与氧同位素曲线的变化趋势相似．末次盛冰期中国东部大陆架覆盖的植被以草地为主，由于冲绳海槽在末次盛冰期时的绝大部分沉积物质与大陆架的剥蚀作用有关，来自长江中上游山地较远距离带来的物质和山地花粉相对减少．与中国东部尘土花粉结果对比发现，现代东海表层蒿属与禾本科比值（A／P）所指示的纬度正好与长江中下游平均纬度相当，而冲绳海槽末次盛冰期的A／P比值所指示的陆地环境比现代高7个纬度，证明末次盛冰期植被带南移，与前人陆地记录的结果相吻合．

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 east- ern China, the ratio of Arternisia/Poaceae from the surface samples of the East China Sea can be evaluated to the correspond- ing 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.