【摘要】 通过对甘肃西峰赵家川6.2～2.4MaB.P.红粘土地层的孢粉学研究,建立了3个孢粉组合带。孢粉组合特征显示该区在此阶段总体为干旱的草原环境,6.2～5.8MaB.P.为灌丛草原;5.8～4.2MaB.P.是稀疏森林草原,植被由大量中生性草本植物和少量喜湿性的乔木植物组成,反映当时气候相对湿润;4.2～2.4MaB.P.植被中旱生植物藜科和麻黄明显增多,反映典型草原-荒漠草原。分析认为研究区自6.2MaB.P.干旱草原环境的格局就已经形成。红粘土中孢粉记录的植被演化信息与青藏高原隆升有时代上的耦合性,也与北极冰盖的起源和演化历史有着密切的联系。更多还原

【Abstract】 The Asian monsoon system is an important component of the global climate, the loess-paleosol deposits from the Chinese Loess Plateau provide an important archive for the evolution of the Asian monsoon and paleoenvironmental changes in East Asia. Recently, the stratigraphy, geochronology, geochemical and sedimentological studies on the Late Cenozoic Red Clay in the Loess Plateau, which conformably underlies the loess-palaeosol successions, have suggested that the bulk of the Red Clay is also wind-blown in origin. Although the study of carbon isotopic has offered some information of vegetation changes from the Red Clay, the detailed vegetation change from pollen records is still not known. Here we present a new continuouse record of palynological data from Red Clay sediments of the Late Miocene-Pliocene from the Xifeng section in the Loess Plateau in central China. Our results show that the Loess Plateau were mainly steppe, indicating a lasting dry climate conditions in the Loess Plateau during the Late Miocene to Pliocene (6.2～2.4MaB.P.). Three ecological zones could be recognized during these periods: Zone A (6.2～5.8MaB.P.)shrub steppe,Zone B (5.8～4.2MaB.P.) wood-steppe, indicating the regional climate being comparatively humid and Zone C (4.2～2.4MaB.P.) steppe to deserted steppe. We suggest that the vegetational changes are correlated with the uplift of the Qinghai-Xizang Plateau during Late Miocene and also coupled with the development of the Arctic ice-sheet.更多还原