青藏高原东南部地貌边界与金沙江水系发育

4000米山顶面高程等值线,可定为高原东南部与外围地区间的地貌界线。低于山顶面的高原面的形成与上新世一早更新世古谷地、盆地的加积相关。元谋运动以来,地貌边界带的发展与高原整体的隆升同步,1500米大河河床高程等值线环绕高原分布,现代水系相继发育。金沙江与长江贯通后东流入海,这是中国大陆地势最终转变为西高东低的标志。

ON MORPHOLOGIC BOUNDARY OF THE SOUTHEASTERN QINGHAI-XIZANG PIATEAU AND DEVELOPMENT OF JINSHA RIVER SYSTEM

Based on the isolines of both the altitudes of summit planes and the altitudes of the major river beds,the morphologic boundary of the southeastern Qinghai-Xizang Plateau and some problems concerned have been studied and discussed in this paper, and then a few important knowledges have been acquired as follows. -1 . The isoline 4000m of the altitudes of the summit planes may be determined the morphologic boundary, thus the upper and' lower boundary belts may be indicated with 4000-4500m . and 4000-3500m respectively. The isoline 3500m of the altitudes of the major river beds all pass through the apexes of the three great meanders of the Yarlung Zongbo, Jinsha and Yaiong Rivers,and they have been mostly located in the upper morphologic bountary belt.2.The summit planes have formed from the last Late Miocene to the initial Pliocene and the plateau planes have been developed beginning with the Late Pliocene and ending off the Early Pleisticene.3.The present continuuos morphologic boundary round the southeastern Plateau has been taken place and made futher advances mainly in the processes that the Plateau has been wholly uplifted since the Middle Pleistocene,with :a total uplift height of about 2000m within the morphologic boundary of the Plateau.4 . There have existed the old valleys of the Jinsha River system to the east of the boundary sector from the Gongga Mountain to Mt. Yulong. However, when the plateau planes, have been cut since the last Early.. Pleislo-cene,those major rivers except the Dadu River, in the southeastern Plateau have been arranged and incised over again by the neotectenic movements and the fault actiotas.5, Linking up of the Changjiang River and its flowing east into the sea has been a major Quaternary geologic event related to a great number of amplitude of the Plateau upheavel,and it has also been a main mark that the Chnia centitient relief of the lo'wer west and the higher east parts before - the Late; Miocene has been turned into ones of the higher Vest and the lower east parts after the. Early Pleistocene.