塔里木盆地北部地区奥陶系层序地层格架与沉积演化*

应用层序地层学和沉积岩石学的原理与方法,深入分析塔里木盆地北部地区(塔北地区)轮南、哈拉哈塘和英买力3个构造单元逾百口钻井的岩心、薄片、测井等资料,结合主要构造运动及海平面变化的研究,建立塔北地区奥陶系层序地层格架,阐述格架内沉积特征及演化。根据区域性不整合界面划分2个二级层序(SSQ1,SSQ2),SSQ1包括下奥陶统—中奥陶统,SSQ2包括中奥陶统—上奥陶统;再根据岩性岩相转换面划分11个三级层序(OSQ1—OSQ11);进一步根据主要海泛面,划分海侵体系域(TST)和高位体系域(HST)。塔北地区奥陶纪沉积环境主要为浅海台地,经历了局限台地—开阔台地—淹没台地—台地边缘的演化过程,最终因陆源碎屑的注入破坏了台地的沉积环境,晚奥陶世塔北地区转为混积台地环境。

Sequence stratigraphic framework and sedimentary evolution of the Ordovician in northern Tarim Basin

According to the theory and approach of sequence stratigraphy and sedimentary petrology,based on thorough analysis of the data of cores,thin sections,well logging in the three tectonic units of Lunnan,Halahatang,Yingmaili in northern Tarim Basin,combining with the previous study on main tectonic events and sea level changes,the sequence stratigraphic framework was estabished and the sedimentary characteristics and evolution were described. According to the regional unconformity surface,two 2nd-order sequences,SSQ1 and SSQ2,were identified. SSQ1 included the Lower and Middle Ordovician,SSQ2 included the Middle and Upper Ordovician. And then,on the basis of lithologic characteristics and lithofacies converting surfaces,eleven 3rd-order sequences(OSQ1-OSQ11)were identified. Further,according to the main marine flooding surfaces,the sequences were divided into transgressive system tract(TST)and highstand system tract(HST). The shallow-sea platform is the main sedimentary environment of the Ordovician in northern Tarim Basin and it experienced the evolutionary process of restricted platform,open platform and platform edge from the Early Ordovician to the Late Ordovician successively. Eventually,as detrital material of terrigenous origin filled in,the platform sedimentary environment in northern Tarim Basin was destroyed and developed into mixed platform.