摘要
西昆仑北坡的新生代沉积在很大程度上良好地记录了新生代西昆仑的隆升过程。区域性不整合面和沉积界面记录了隆升的阶段性;沉积环境变化反映了山体和盆地在格局上的变化;沉积物厚度、粒度变化显示了隆升的幅度和速率。就西昆仑的情况看,海相环境(塔里木海湾)由晚白垩世持续到渐新世,尽管此时海湾已退缩到西部。在此期间,形成了石膏层、瓣鳃类介壳灰岩和杂色砂泥质沉积。中新世全面出现了陆相沉积。中新世2000～3000m的沉积厚度表明了相对较高的隆升速率。从中新世后期开始的厚达2000～3000m的磨拉石沉积,其粒度向上加大,显示从中新世后期到早更新世隆升速率高而且是加速的。磨拉石沉积被早更新世的一次强烈的构造脉动所打断,它使磨拉石沉积和较老的沉积在许多地方高角度向盆地方向倾斜甚至直立、倒转。水平盖在磨拉石和更老地层之上的中—晚更新世河流和冲积扇相粗粒沉积是重新隆升的标志,亦可视为磨拉石沉积的继续。由昆仑山流向塔里木盆地的河流将中—上更新统及更老沉积切割50～100m以上,表明全新世以来的隆升速率是相当高的。
The uplifting of the West Kunlun, or more exactly the relative motion between the West Kunlun and the Tarim basin, in the Cenozoic is, to a large extent, well documented by Cenozoic sediments at the northern margin of the West Kunlun. Regional unconformities and sedimentary boundaries record the rhythm of uplifting; sedimentary environment change (coastal marine to lacustrine to fluviatile, alluvial, pluvial fans) notes the variation of the mountain-basin configuration; and thickness and grain size of Cenozoic lithological units may reveal the amplitude and rate of the uplifting.Marine environment (the Tarim Bay) was sustained from the latest Cretaceous to the Oligocene, although it had already retreated to the western part at that time. During this period, gypsum beds, bivalve shell limestone and variegated elastics were formed. 2000 to 3000 m thick Miocene sediments indicate a relatively higher uplifting rate. 2000-3000 m of molasse started in the late Miocene and with a coarsening-up tendency show a rapid and accelerated uplifting from the late Miocene to early Pleistocene. The deposition of molasse was interrupted by a tectonic pulse in the early Pleistocene, which resulted in the high-angle tipping or even being upright and over-turned of the molasse and underlying older sediments. Horizontal middle to late Pleistocene fluvial and pluvial coarse deposits overlying the molasse and older rocks represent the resumption of uplifting, which can also be considered as the continuation of molasse formation. That rivers flowing from the West Kunlun to the Tarim basin cut the middle to late Pleistocene gravel beds and older sediments to a depth of 50 to more than 100 m indicates a high uplifting rate since the Holocene.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2001年第4期459-467,共9页
Acta Geologica Sinica
基金
国土资源部"九五"重点基础项目(编号9501101)资助成果
