【摘要】 <正> 一、区域自然地理背景 洞庭盆地位于荆江南岸,跨湘鄂两省,总面积18,780km~2,周围群山环抱,中央为辽阔的冲积平原。自湖盆周围向中心地带,低山、丘陵、阶地、平原呈层状分布,逐级降低,明显地可分为三至四级。盆地中心则为多级阶地和50m以下的冲积平原。这里河湖密布、堤垸交错、地势低平,主要是长江及其支流湘、资、沅、澧诸水形成的泛滥平原。整个盆地的更多还原

【Abstract】 Based on the formation of sedimentary facies and the sporopollen assemblages derived from drilling cores of Huatian and Anyou in the Dongting basin and comparison with other boring profiles of the region, the natural environmental changes of the basin during the Quaternary period can be summarized as follows:There are eighteen rhythmic successions of grain size in the Huatian boring profile (Drill Hole Tian 11) and seven rhythmic successions in the Anyou boring profile (Drill Hole CK. 10). They represent four different sedimentary periods (Q1; Q2, Q3, Q4). The series of sediments belongs to cyclothem of fluvial facies and reflects that brooklets and lakes interwove here and tliere on the basin and these water bodies were often wandering in nature. This denotes that the supposed existence of a great lake embracing the entire Dongting basin during the Quaternary period is inconceivable.The Huatian boring profile can be subdivided into six vegetational zones in the following ascending order: evergreen broad and deciduous broad-leaved forest, herb-shrubby fern and aquatic plants, needle-leaved and deciduous broad-leaved mixed forest, deciduous broad-leaved forest, deciduous broad and evergreen broad-leaved mixed forest, and herb-shrubby fern (with deciduous broad-leaved trees) and aquatic plants (Tab. 1), corresponding climatic changes of wet-hot, temperate, cold-temperate, warm, temperate-hot and wet-hot respectively.From the above-mentioned conditions, it is clear that the world-wide alternate cold and hot climate in the Quaternary period did not affect the climate of this region as much as of the northern part of China. We hold that this has been due mainly to the continuous uplift of the Qinling Mountains since the Quaternary, preventing the arid-cold flows of Siberian anticyclone from passing southward. In the meantime, owing to the effects of southeastern monsoon, the climate of southern China (taking Qinling Mountains as the dividing line), remained humid. In other words, during the glacial and interglacial periods, the climate was less influenced in southern China than in northern. Therefore the opinion about the presence of ancient glacier in the east part of China during the Quaternary is worth reconsidering.更多还原