摘要
在长江中游的洪湖、东湖、网湖和大九湖等四个地点取得湖沼沉积物的钻孔样品 ,用偏光显微镜下和电子显微镜观察微结构特征并以此解释三种湖相粘土的成因和沉积环境的变化。在长江沿岸湖泊中 ,0 .4～ 0 .5kaBP以来形成的浅色粘土的微结构类型主要有 :显微层理构造、颗粒的定向性、较大的微孔隙和颗粒粒径 ,面与面或边与边接触方式。物源主要来自河流带来的泥沙 .当时河湖相通 ,河流入湖水沙量大。 1～ 2 .5kaBP期间形成的青色粘土的典型微结构是 :凝胶结构、絮凝结构、细颗粒粒径和小孔隙、低球度和淡水中心冈硅藻。主要是有机质胶体与粘土胶体相互作用形成的。此期间 ,河流带入湖泊的泥沙少 ,江汉平原拥有一个开阔、稳定、浮游生物较多的淡水湖泊环境。 0 .4～ 1kaBP期间形成的黑色粘土的主要微结构类型是 :凝胶结构、大的圆孔隙和植物纤维的生物框架结构、呈双峰分布的孔隙。它主要是由于维管束植物残体大量积累形成的。当时江汉平原湖泊湖水变浅 ,大量挺水植物生长 ,有些湖泊沼已经沼泽化了。鱼骨框架结构证明 ,在 2 .9～ 4kaBP的全新世温暖期山间盆地大九湖出现大量鱼类 ,但并没有导致喜温鱼类向上游明显迁徙。
Mircrofabrics from core sediments were observed in polarizing microscope and scanning microscope and used in interpreting the origin of three types of clay as well as the changes of sedimentary environments in four sites-the Honghu Lake,the Donghu Lake,the Wanghu Lake and the Dajiuhu Lake along the middle reach of the Yangtze River.Micro-beddings,orientation of particles and large sizes of micro-voids and particles with contacting patterns of face to face or edge to edge occurred in the light-colored clay formed since 0.4～0.5ka BP in the lakes.Their origin was ascirbed to clastic sediments from rivers surrounding the lakes.It was suggested that the lakes were connected with rivers and large amount of sedimens came from rivers into the lakes during that period.The typical microfabrics in the blue clay formed in 1～2.5ka BP were gelatinous texture,agglutinational texture,small sizes of particles and voids,low sphericity and diatoms of freshwater Class Centrium .Their origin was ascribed to the result of the interaction between organic colloids and clay colloids.It was suggested that the lakes in the Jianghan plain were of open and stable fresh water lake environments rich in planktons and with small amount of clay carried by rivers during this period.The main microfabrics in the black clay formed during 0.4～1ka Bp were gelatinous texture,large circular voids and plant fiber.The voids had a bimodal distribution.The sediment was formed mainly due to the accumulation of large amount of aquatic vascular bundle plants.It was suggested that the lakes were shallow and rich in aquatic vascular bundle plants,and some of them were swamping.The framework of fish bone in the sediments indicated that there was large number of fish in the Dajiuhu area during the Holocene warm period of 2.9～4ka BP,but the thermophilous fish did not migrate upwards apparently.
出处
《沉积学报》
CAS
CSCD
北大核心
2002年第2期293-302,共10页
Acta Sedimentologica Sinica
基金
国家自然科学基金 (批准号 :4950 1 0 0 3和 49971 0 81 )
中国科学院水生生物研究所东湖生态实验站 (2 0 0 1 0 5)
中国科学院‘九五’重大项目ZK951 A1 2 0 2 0 1 0 3资助
关键词
沉积环境
微结构
湖相粘土
成因
环境变化
长江中游
东湖
洪湖
网湖
microfabric, origin of lacustrine clay, environmental changes, the middle reach of the Yangtze River, Donghu Lake, Honghu Lake, Wanghu Lake, Dajiuhu Lake
