江汉盆地始新世中、晚期孢粉组合特征及其环境意义

本文依据明钾1井孢粉分析资料建立了江汉盆地始新世中、晚期的孢粉组合序列，共划分出6个孢粉带、14个孢粉亚带、6个孢粉植物群-气候时期和5次孢粉植物群气候事件。孢粉证据揭示，在始新世晚期存在着一次剧烈的环境变革，植被经历了由阔叶针叶混交林向阔叶林的转化，气候由中亚热带干旱-半干旱气候向北亚热带湿润-半湿润的转化。孢粉植物群气候事件由前三次快速而强烈的干湿、暖热颤动事件，转化为后两次气候转型事件，气候由暖湿、热干转为热湿、暖干。在盐岩-钙芒硝泥岩-紫色泥岩-泥灰岩-泥岩-粉砂岩的岩石序列中孢粉组合呈现有规律的变化，反映出气候干湿变化对植被和沉积环境的制约作用。盐类堆积时期，当地地形起伏大，植被稀疏；湖滨周围耐旱麻黄灌丛发育，气候干旱、偏热；山区有针叶、阔叶疏林分布，气候偏湿。

A Study of Middle and Late Eocene Palynological Assemblages in Jianghan Basin and Their Environmental Significance

On the basis of pollen analyses of samples from the Mingjia No. 1 borehole, the Middle and Late Eocene pollen assemblage sequences in Jianghan basin were studied. Six zones and fourteen subzones were distinguished. It is thought that the evolution of vegetation can be divided into four periods, during which conifer and broad-leaf mixed forest changed gradually into broad-leaf forest. Six climate periods can be recognized. At the beginning, there was a kind of arid or semiarid climate of mid-subtropics, which then gradually converted into most or sub-moist climate of North subtropics. In the course of transformation, totally five times of climate abrupt change, i.e., palynoflora climate events, appeared. The first three events belonged to quick and intense oscillation events from drought to most and from warm to hot, whereas the last two belonged to the climate transformation evnets, in which the warm and wet or hot and dry climate became hot and wet or warm and dry. In the saltstone? glauberite mudstone? purple mudstone? marl mudstone? siltstone rock sequence, the palynological assemblages changed in accordance with some regularities. These changes indicate that the fluctuation of clamate could govern the changes of vegetation and sediment environment.