金沙江川滇交界段构造-地貌特征

STRUCTURAL-GEOMORPHIC FEATURES OF THE JINSHA RIVER SECTOR IN THE SICHUAN-YUNNAN BOUNDARY REGION

金沙江川滇交界段的构造-地貌在长江流域中颇具特色。这里有高逾5500米的终年雪山,有相对高差达3700米的大峡谷,有多种类型的冰川-冰蚀地貌和冰蚀湖、高原夷平面等。在奇特而多样的地貌类型中,最具特色的是金沙江的5处大改流,其中前3处改流所形成的主江道巨大拐弯,在长江流域是很引人注目的。如果说帕米尔、青藏高原是亚洲大陆的两处神秘地区,那么,川滇交界地区的金沙江段也颇具神秘色彩。 (一)对金沙江几处大改流的见解(图1)

In the Yangtze River drainage area, the structure-geomorphy of the Jinsha River sector in the Sichuan-Yunnan boundary region is very characteristic. In this region, the flow direction, of the Jinsha River changes abruptly at five spots, which are Shigu of Lijiang, Sanjiangkou of Yongning, north of Binchuan, Dukou-Sanduizi and Lazha-Yuzha successively from the upper to the lower. The causes of the abrupt changes are erosion of the river water in the fault zone of neotectonics, barricade of mountains risen in the earlier Neozoic or pre-Neozoic, and river abstraction, etc. There are many kinds of geomorphy formed by ice erosion in this region, and glacial-erosion lake, terrace, horn, U-valley, glacial tongue, cirque, and bladed ridge are dispersed widely. In this region, active structures are widely developed, the activity is intensive and earthquakes occur frequently, which can be divided into Baiyu-Batang, Jianchuan-Dali, Jinhe River-Erhai Lake, Xianshui River-Zemu River, Anning River five active structure divisions. In Tertiary-early Quaternary, the subduction and intensive press of the Indian plate towards the Eurasian plate was the basic factor of the formation of the stress pattern and the control of the structure-geomorphy evolution in this region.