川东南地区茅口组层序地层及沉积相浅析

Analysis of sequence stratigraphy and sedimentary facies of Maokou Formation in southeastern Sichuan

在对川东南地区茅口组沉积背景认识的基础上,利用野外剖面及录井、测井资料,将茅口组划分为3个三级层序,通过研究岩性、相序及岩性剖面结构,阐明了层序关键界面识别与划分的标志,分析了各体系域特征。认为研究区茅口期具有快速海侵、缓慢海退的特点,层序对比良好,且具陆表海台地性质。按陆表海沉积模式将研究区划分为潮下低能带、潮下高能带及潮坪、泻湖等沉积相带,以体系域为单元从纵向上和平面上对沉积相进行了精细刻画。最终,结合层序及沉积相演化,提出了茅口组层序格架内的沉积模式。

On the basis of the knowledge of the depositional setting of Maokou Formation in southeastern Sichuan,Combined with outcrop,well log and well logging data,the Maokou Formation is divided into three third-order sequences.Accordingtothe research on the lithology,phase sequence and lithologic profile,the sign for identifying and classifying the key sequence surface is expounded,and the characteristics of the every system tracts are summarized.It is believed that the strata at Maokou stage in the study area have the characteristics of rapid transgression and slow regression,well sequence comparison and epicontinental platform nature.Therefore,according to the depositional model of epicontinental platform,the sedimentary facies in the study area can be divided into subtidal lowenergy zone,subtidal high energy zone,tide flat and lagoon.The sedimentary facies on the vertical and plane profile is described makingthe systemtract as unit.Combined with the sequence and the evolution of the sedimentary facies,the depositional model of Maokou Formation is proposed.The beach facies being favorable for reservoir development mainly develops in the high-stand systemtract.