黑龙江鸡东盆地中中新世湖盆演变和植被变化研究

LAKE AND VEGETATION HISTORY IN THE MIDDLE MIOCENE JIDONG BASIN,HEILONGJIANG PROVINCE,NE CHINA

黑龙江鸡东盆地是受古、新近纪敦密断裂带作用而形成的断陷含煤盆地。依据该盆地91-205钻孔永庆组的岩性变化特点和盆地构造演化阶段,识别和阐述了中中新世湖盆发育的3个阶段,即早期湖泊形成发展阶段、中期湖泊扩张最大阶段和晚期湖泊收缩衰退阶段,并揭示湖泊阶段性发展的旋回性特征。根据孢粉资料,恢复湖盆各个不同发育阶段的古植被面貌,重建当时的古气候。结果表明植被经历了北亚热带含常绿阔叶成分的落叶阔叶林、暖温带—北亚热带落叶阔叶林以及含亚高山针叶树种的暖温带—北亚热带落叶阔叶林阶段,鸡东盆地中中新世湖泊的演变和植被更替存在着潜在的关联。

The Jidong Basin, bounded by the Dunhua-Mishan Fault, was a Neogene lacustrine coal-bearing basin. Its evolutionary history in Miocene is still rather poorly understood. In the context of the tectonic settings, cyclic variation in lithology of the Yongqing Formation from the borehole 91-205 allows us to unveil the Miocene history of the Jidong Basin. Evidence indicates that the palaeolake underwent three main stages. These are the initial stage, the maximal development stage, and the retreat stage, in which two minor lake evolution cycles are also recognized. Vegetation succession and landscape change in the study area are described on the basis of rich pollen fossils from a total of 64 samples from the Yongqing Formation. Variations in relative abundance of Ulmus , Alnus , Tilia , Carya , Liquidambar , Quercus , Pinus and other taxa suggest vegetation changed in each lake development stage. In correspondence to the three lake development stages, vegetation evolved from deciduous forests with northern subtropic evergreen trees, through deciduous forests in a warm temperate to northern subtropic climate, to broadleaved deciduous forests with alpine trees. It is possible that vegetation evolution and lake development in the middle Miocene Jidong Basin were related in some ways.