现代黄河三角洲北岸1.9Ma以来孢粉组合及古环境变化

通过对现代黄河三角洲地区YRD-1101钻孔的沉积地层研究和孢粉分析，认为该地区1.9 Ma以来孢粉组合代表的植被面貌自下而上表现为:针叶阔叶混交林—灌丛草甸→落叶针叶—阔叶混交林→落叶阔叶林→常绿阔叶落叶林→针叶阔叶混交林→落叶阔叶混交林→针叶落叶混交林及灌丛草甸→落叶阔叶混交林及林下灌丛。YRD-1101钻孔沉积特征变化显著，孢粉组合波动频繁。第四纪期间存在3次大的气候拐点，分别发生在0.75 Ma，0.125 Ma和9.1 ka，气候整体表现为温度逐渐上升、湿度逐渐升高的特点。特别是晚更新世以来气候趋于温暖湿润，MIS2陆相沉积阶段气候短暂转为凉爽干燥，海平面下降，植被以耐干旱草地灌丛植被扩张为特点；全新世阶段气温升高、湿度增加，海平面上升，植被以木本植物再次扩张、蕨类和藻类增加为特点。这一趋势与我国第四纪海侵地层分布及范围一致。

Pollen Assemblages and Induced Palaeoenvironmental Changes in the Yellow River Delta Since 1.9 Ma

The study of core YRD-1101 from the Yellow River Delta on sediment lithology， multi-method dating， and high resolution spore-pollen data suggests that the changes in pollen assemblage since 1.9 Ma have resulted from the joint effects of vegetation， climate， and sea-level changes， which show a regular pattern of variation， including deciduous coniferous forest shrub meadow， deciduous coniferous broad-leaved mixed forest， deciduous broad-leaved forest， evergreen broad-leaved deciduous forest， coniferous broad-leaved mixed forest， deciduous broad-leaved mixed forest， coniferous and deciduous mixed forest and shrub meadow， deciduous broad-leaved mixed forest. and under forest shrub. There are three major climate turning points during the Quaternary period， which occurred at 0.75 Ma， 0.125 Ma， and 9.1 ka， respectively. The points indicate a frequent alternation of warm-wet and cold （coo1） -dry climatic conditions， in addition to significant sea level fluctuation. In general， the climate shows a rising trend for temperature and humidity， especially since the Late Pleistocene. The continental sedimentary stage turned to a cool and dry climate， and the grassland shrub vegetation expanded while the sea level decreased during the MIS2 stage. The palaeotemperature rose and the woody plants expanded again while the proportion of ferns and algae continued to rise， along with the sea level rise in Holocene， which are similar with the distribution and range of Quaternary transgressive strata in China.