金沙江中游云南龙街粉砂层沉积环境演化特征

摘要

沿金沙江攀枝花三堆子至武定县白马口段河谷两岸分布一套以灰黑色、灰黄色、灰白色粉砂、粘土质粉砂和粘土为主的湖相地层，尤以云南省元谋县龙街盆地内最为发育，被称为龙街粉砂层。通过龙街YA钻孔和龙街、白泥湾剖面的磁性地层学和光释光年代学的研究，探讨龙街粉砂层的时代与归属。龙街YA钻孔地层厚度101.18m，其中龙街粉砂层厚92.96m，上覆7.5m的红棕色细砂和砂砾石层，下伏厚度大于0.72m的灰绿色含角砾粗砂。综合分析YA钻孔的磁性地层学和光释光年龄，认为获取龙街粉砂层的沉积时代为150~30ka BP，属于晚更新世。通过地层沉积特征变化，反演晚更新世以来湖泊的形成及沉积环境变化，探讨晚更新世以来区域新构造的活动阶段及其对河流演化过程的控制作用。%The Longjie silt layer consists of a series of silt, silty clay and clay lacustrine sediments which are grayish black, grayish yel⁃low and grayish white in color. This silt layer is distributed along the valley of the Jinsha River from Sanduizi of Panzhihua City to Baimakou of Wuding County, and is well developed in the Longjie basin in Yunnan Province. The Longjie drill hole intersects the stratatigraphic thickness of 101.18m, which includes 92.96m Longjie silt layer. Its sedimentation occurred about 150~30ka BP, as shown by the analysis of magnetostratigraphy and OSL dating. Through the study of sedimentary variation characteristics, this paper deals with the formation process of Longjie silt layer, the relative regional neotectonics movement stage and its influence on the devel⁃opment of the Jinsha River.