晚新生代元谋盆地演化与河谷发育研究

Studies on Development of Yuanmou Basin and Valleys during Late Cenozoic

元谋盆地是在晚新生代青藏高原与云南高原隆起过程中形成的众多断陷盆地之一，流经元谋盆地的龙川江和金沙江，其河谷发育与盆地演化具有密切关系．通过对元谋盆地及其邻区的层状地貌与相关沉积的分析研究，认为，始新世晚期～中新世晚期是夷平面形成时期，中新世晚期～３．４０ＭａＢＰ前后是第一级剥蚀面形成时期；元谋盆地形成于３．４０ＭａＢＰ前后第一级剥蚀面解体过程中，其后盆地经历了３．４０～１．７８ＭａＢＰ的古湖形成与１．７８ＭａＢＰ构造活动事件之后的沟谷发展两个阶段；古湖时期的古水系是以古湖为归宿的内流水系，现代的龙川江和金沙江是在盆地抬升、古湖消亡的过程中形成的，时代为（１．７８～１．５４）±０．１７８ＭａＢＰ．

The Yuanmou Basin is one of the basins which formed during the uplift process of the Qinghai Xizang and the Yunnan Plateaus. Longchuanjiang River and Jinshajiang River pass through the Yuanmou Basin. The development of the valleys is related to the development of the Yuanmou Basin. By analyzing the stratified geomorphological surfaces and their relative sediments, the planation surface was considered to be formed from Late Eocene to Late Miocene, the first denudation surface from Late Miocene to 3.40 Ma BP, and the Yuanmou Basin at about 3.40 Ma BP. when intense tectonic movement disintegrated the first denudation surface. Thereafter, the development of the basin experienced two stages, i.e. paleolake formation stage from 3.40 to 1.87 Ma BP and valley development stage after the tectonic event at 1.87 Ma BP. The drainage pattern in the palaeolake stage was an interior one which flowed into the palaeolake. Modern rivers, including the Jinshajiang River and the Longchuanjiang River, were formed due to the uplift of the basin and the withering of the palaeolake. The formation time of modern rivers was no earlier than 1.78 Ma BP.