塔里木盆地早古生代晚期构造-沉积响应

伴随相对海平面由上升转为下降的周期变化,塔里木盆地在早古生代经历了一次大规模的扩张→挤压→隆升的开合旋回,早期(震旦纪-中奥陶世)处于拉张的构造背景下,呈现西台(碳酸盐台地)东盆(满加尔-库鲁克塔格深水盆地)的古地理格局。中西部广大地区沉积了巨厚的浅水台地相碳酸盐岩,以中晚寒武世的下丘里塔格群和早中奥陶世的上丘里塔格群为标志;东部的满加尔-库鲁克塔格则以厚度不大的远洋硅-灰泥沉积为主。盆地构造性质的转换及沉积古地理的巨大改变发生于中奥陶世中晚期,以塔中、塔北的隆起和塘古孜巴斯坳陷及阿瓦提-满加尔坳陷的形成为标志,呈近南北向隆-坳相间的盆地格局。沉积记录的响应表现为碳酸盐台地的消失、陆源物质的逐渐注入和向上变粗、火山活动和火山碎屑的出现以及巨厚砂泥质浊积岩在塔东盆地内的充填等。因此,中晚奥陶世-中泥盆世是塔里木盆地海域逐渐萎缩、盆地不断隆升和相对海平面逐渐下降的一个过程。

Tectonic-sedimentary responses of the Tarim Basin, Xinjiang during the late Early Palaeozoic

The Tarim Basin recorded a large-scale spreading- compression-uplifting cycle during the Early Palaeozoic. During the early Early Palaeozoic (Sinian-Middle Ordovician), the basin was in the extensional setting and displayed a palaeogeographic framework composed of a platform (carbonate platform) in the west and a basin (Manjiar-Kuruktag deep-water basin) in the east. There deposited the thick shallow-water platform carbonate rocks represented by the Middle-Upper Cambrian Lower Qiulitag Group and Lower-Middle Ordovician Upper Qiulitag Group in the west-central part, while the pelagic siliceous and limy mudstones in the Manjiar-Kuruktag deep-water basin in the east. The great changes of tectonic background and sedimentary facies and palaeogeography of the basin took place during the middle-late Middle Ordovician. The nearly NS-trending (uplift)-(depression) framework of the basin is well represented by the Central and Northern Tarim uplifts, Tangguzibasi and (Awat)-(Manjiar) depressions. The sedimentary responses are manifested in the disappearance of the carbonate (platforms), influx of the terrigenous clastics and coarsening upwards, appearance of volcanic activity and volcanic clastics, and infilling of thick sandy and muddy turbidites in eastern Tarim Basin. It can be seen that the (Middle)-(Late) Ordovician and Middle Devonian times are believed to be significant for the collapse of the sea area, (uplifting) of the basin, and falling of the relative sea level.