汉代至元代北京什刹海成湖的地层证据 —— 以小石碑胡同工地西壁南剖面为例

对北京什刹海北岸小石碑胡同工地西壁剖面沉积物粒度、化学成分及孢粉等相关数据进行综合分析, 结果表明, 从汉代至元代, 什刹海有4 个环境演变阶段的沉积物: 1930~1820 aBP 为河流相的分支河道、河漫滩沉积; 1820~1295 aBP 为湖泊沉积, 其中三国时期(1730~1690 aBP)水域较大, 水体较深, 可能与车箱渠的修筑有关, 此后逐渐退为湖滩; 1295~970 aBP 为河流相沉积; 970~580 aBP 为湖滩沉积, 是当时什刹海北岸的边缘地带。孢粉组合反映低湿地植被的环境特点, 符合该地区沉积物的环境背景特征。元代湖岸距当时的斜街约100 m, 距今什刹海北岸约80 m。研究结果揭示了什刹海湖泊演变的历史, 为什刹海环境演变研究乃至北京城区的历史地理研究提供基础性资料。

Evidence in Stratum for Shichahai Becaming Lake from Han-Dynasty to Yuan-Dynasty: A Case of the Southern Section at the Western Side of Building Site in Xiaoshibei Hutong

Based on the synthetically analysis to the data of the granularity, the chemical index and the sporopollen of the sectional sediments which belong to the building site located in Xiaoshibeihutong at the north bank of Shichahai, it shows the geomorphic changes of Shichahai from Han-Dynasty to Yuan-Dynasty. The changes can be divided into four parts according to the different periods. From 1930 to 1820 aBP, as the sediment of river form, it owns the branchchannel and sediment of fluvial facies. From 1820 to 1295 aBP, as the sediment of lake form lacustrine facies, especially from the end of Eastern-Han-Dynasty to Three-State-Period, it owns larger aquatorium and deeper water. During this time, the Chexiangqu was being built, thus it may have the man-made impoundment, but then it became lakeshore. From 1295 to 970 aBP, it is the sediment of fluvial facies. From 970 to 580 aBP, as the sediment of lakeshore, it would be the brim of north bank of Shichahai at that time. The series of sporopollen indicate not only the climate changes of this section, but also the characteristics of the vegetation in the carse relating to the local landform. It is found that the distance between the lakeshore in Yuan-Dynasty and Xie- Street in Yuan-Dynasty is about 100 meters, while the distance between the lakeshore in Yuan-Dynasty and the north bank of Shichahai is 80 meters. By analyzing the palaeoenvironment index of this section and the historical documents, the environmental envolution at Shichahai could be revealed, especially at this site, which provides the basic information for researching the environment changes of Shichahai.