库车前陆盆地三叠系层序地层研究

Triassic sequence stratigraphy in Kuqa foreland basin

综合分析库车前陆盆地三叠系地震、测井、钻井、露头资料 ,识别出 13个层序边界 ,划分出 12个层序和 33个体系域 ,建立两种层序地层学框架模式 :①早三叠世至晚三叠世黄山街组沉积末期 ,具有典型前陆盆地挤压深陷特征 ,层序地层框架模式与内部构成类似于Vail的被动大陆边缘型盆地 ;②晚三叠世塔里奇克组沉积期至白垩纪末期 ,具有宽缓、伸展的特点 ,层序地层框架模式及内部地层构成样式有其独特性。层序发育主要受构造运动、古气候及沉积物供给的影响。控制湖平面或基准面变化的主要因素是构造活动 ,造山运动强烈期是主要的湖进期 ,构造运动相对静止期是主要的湖退期 ,气候变化主要影响层序地层格架内的沉积相类型。图 4表 1参 8(何宏摘 )

A systematic study on Triassic sequence stratigraphy in Kuqa foreland basin has been carried out by integration of seismic, logging and drilling data and outcrop survey. 13 sequences' boundaries have been identified, and they were divided into 12 sequences and 33 system tracts. Two different models of sequence stratigraphic framework were established through studying the internal composition of sequence strata and boundary of individual sequences. From early Triassic to the end of Huangshanjie stage of late Triassic, this basin appeared as a strong compressive piedmont alluvial-hungry basin, a typical foreland basin. The model of the sequence stratigraphic framework and its internal composition are similar to that of Vail's passive continental marginal basin, respectively. In contrast, from Taliqike stage of late Triassic to the end of Cretaceous, the basin shows smooth and expansive features, and has a unique model of sequence stratigraphy framework and its special internal stratigraphic composition. The evolution of sequences was mainly controlled by regional tectonic activities, paleoclimate and sediment supplies. The main factors controlling the changes of lake or base-level are orogenic episodes of the tectonic activities. The period for the lake to be deepened as a result of strong orogeny is the major period of lake transgression whilst the stage of the relatively weak orogeny is the major period of lake degression. The changes of climate mainly impacted on sedimentary facies within sequence frameworks.