论文部分内容阅读
洱海是位于云南省境内较大的但相对较浅的断陷湖泊（水深小于２０ｍ）根据１９９０－１９９３年对该湖现代沉积的研究，结果表明，湖泊沉积物主要来自西部相对高２０００ｍ以上的山地，东部为低矮石灰岩山地，物源较少，南北两条入湖河流亦是重要的物源供应区．湖区沉积物主要是由粉砂质粘土组成，来自山地的粗碎屑物质则大量的堆积于此地，三角洲、扇三角洲及滨湖地带，沉积速率在过去 １３０００年中平均为０．２ｃｍ ａ－１，相当于全湖平均每年堆积约６００ ｔ ａ－１，这个量也相当于 １９９２年 ２月湖中悬浮物总量．这也表明丰富的陆源供给（雨季降雨，植被破坏和地震等），并说明了持续浅水湖泊的存在．湖泊沉积作用也受到内部因素影响而复杂化，如湖流作用使沉积物重新分布并扩展至整个湖底在现代沉积物中，水下滑坡和滑塌尚少见．对沉积物化学分析表明，其反映了周边岩石和土壤组成，包括生物成因的成份（主要是植硅石）．沉积物微量元素相对较丰，可能系土壤渗漏、污染或细粒沉积物携带所致．
Erhai Lake is a large but relatively shallow rift lake (less than 20 m deep) in Yunnan Province. Based on a study of the modern deposition of the lake from 1990 to 1993, it shows that lake sediments are mainly from mountainous areas relatively high in the west of 2000 m , East of low limestone mountains, less provenance, north and south into the lake is also an important source of supply. Sediments in the lake area are mainly composed of silty clay, while coarse detrital materials from the mountains accumulate in this area, delta, fan delta and lakeshore areas. The sedimentation rate has been 0.2cm a-1 on average over the past 13,000 years , Equivalent to an average annual accumulation of about 600 t a-1 in the whole lake. This amount is also equivalent to the total suspended matter in the lake in February 1992. It also shows abundant land-based supplies (rainfall in the rainy season, vegetation damage and earthquakes, etc.) and illustrates the existence of persistent shallow lakes. The sedimentation of lakes is also complicated by internal factors. For example, the lake flow redistributes the sediments and extends to the entire lake bottom in modern sediments. However, underwater landslides and landslides are still rare. Chemical analyzes of sediments show that they reflect the composition of the surrounding rock and soil, including biogenic components (mainly phytoliths). Trace elements in sediments are relatively abundant, probably due to soil seepage, contamination or fine-grained sediments.