塔里木西南早第三纪古地磁和地壳缩短  

EARLY TERTIARY PALAEOMAGNETISIM AND CRUSTAL SHORTENING IN SOUTHWEST TARIM

作　　者：薛耀松[1] 虞子冶[1] 

机构地区：[1]中国科学院南京地质古生物研究所

出　　处：《新疆地质》1996年第2期143-150,共8页Xinjiang Geology

摘　　要：属于帕米尔弧山前带的乌帕尔剖面和属于南天山山前带的巴对布拉克剖面，现今的纬度差为０．５６°，但是下第三系古地磁测定结果表明其古纬度差很大．乌帕尔剖面齐姆根组上部的古纬度为８°Ｎ，而巴什布拉克剖面巴什布拉克组第５段的古纬度为３６．１°Ｎ。若考虑到当时板块的相对运移速度，估计始新世早期巴什布拉克地区的古纬度大致为３１°Ｎ，与当时乌帕尔所处位置的纬差达２３°。又根据Ｋｌｏｏｔｗｉｊｋ测得的帕米尔西北缘利什坦层的古纬度值，在始新世末期．包括乌帕尔在内的帕米尔前缘与以巴什布拉区为代表的南天山山前带之间还有至少１０°的纬度差。古地磁资料表明，始新世早期，塔里木海宽达２０００ｋｍ，此时印度板块西北端已与欧亚板块局部碰撞，至始新世末，印度板块向北推进２０°，帕米尔弧前缘与南天山山前的距离缩短到约１０００ｋｍ，原塔里木海的两侧上升为山前平原。The present latitudinal difference is only 0. 56°between Upar section and the piedmont of Parmir arc,and Bashbulak section at the piedment of South Tianshan. But palaeomagnetic dating results of Lower Tertiary show great difference. The palaeolatitude at the upper Qimugen Formation of Upar section is 8°N,while that of the 5th bed of Bashbulak Formation of Bashbulak is 36. 1°N. It's estimated,from the relative migrating velocity of plates at that time,that the palaeolatitude of Bashbulak area at the early Eoccene is 31°N,a difference of 23°from Upar area. And according to the palaeolatitude mesured by Klootwijk from Lishtan bed at northwestern margin of Pamir,the palaeolatitudinal difference is 10°at least at the end of Eocene between the frontal margin of Pamir including Upar,and piedmont of south Tianshan represented by Bashbulak. The palaeomagnetic data show that the Tarim Sea was as wide as 2 000 km at the early Eocene,and at the same time the northwestern end of India plate collided locally with Eurasia plate. Up to the end of Eocene,the India plate progressed northward 20°,and the distance between frontal margin of Pamir and piedmont area of South Tianshan was shortened about 1 000 km,and both sides of Tarim sea were uplifted to form piedmont plateau.

关 键 词：塔里木 古地磁 古纬度 板块碰撞 地壳缩短 

分 类 号：P318[天文地球—固体地球物理学]