论沉积层序级别的划分

沉积层序的级别有２种划分系统，分别以基准面变化的相对频率和相对振幅为基础。介绍与评述了这２种划分系统，并提出了针对塔里木盆地沉积层序级别划分的建议。在塔里木盆地已识别出来的２４个３级层序的基础上，按不整合面积占层序边界面积的不同比例，将震旦系到第四系地层划分为６个１级层序和１４个２级层序。古生界地层的１级层序与构造层不一致，反映了塔里木克拉通盆地阶段除构造活动外，还存在海平面变化的强烈影响；中、新生界地层的１级层序与构造层相符，反映了塔里木前陆盆地阶段构造活动对层序形成起着决定性作用。由于构造活动是形成１级至３级层序的主控因素之一，而不同盆地的构造背景和构造运动发生的时间、活动强度大都不同，因此，各盆地都有其独特层序级别系统。图５表１参１１（邹冬平摘）

Classification of depositional sequence hierarchies.

Two classification systems of depositional sequence hierarchies are respectively presented, which are based on the relative frequency and relative magnitude of base level changes. The classification of sequence hierarchy of the Tarim basin is discussed. On the basis of 24 recognized third order sequences, the strata of the Tarim basin from the Sinian to Quaternary systems are divided into 6 first order sequences that consist of 14 second order sequences according to the different ratios of unconformity surface over sequence boundary extent. The Paleozoic first order sequences in the Tarim basin are not consistent with the Paleozoic synthems, which reflects strong effects of sea level changes besides tectonic activities during the cratonic stage of the Tarim basin; whereas the Meso Cenozoic first order sequences are consistent with the Meso Cenozoic synthems, which reflects the most important role of tectonic activities in formation of first order sequence during the foreland stage of the Tarim basin. Every basin should have its own unique hierarchy of sequence orders because tectonic activities are one of main control factors for formation of first through third order sequences and tectonic background, time and intensity of tectonic activities are very different from one basin to another.