兰坪盆地古近系宝相寺组层序地层分析

Sequence stratigraphy analysis of Paleogene Baoxiangsi formation in Lanping basin

文章运用层序地层学原理,对兰坪盆地中部古近系宝相寺组进行深入研究,划分出1个Ⅰ型层序及3个Ⅱ型层序界面。阐述了兰坪盆地中部古近系宝相寺组层序格架及砂体结构特征,建立层序地层格架演化模式图,反映了湖平面变化对砂体沉积结构的重要影响。低位体系域早期河流侵蚀强烈,多以中粒为主,晚期发育复合状砂体;湖侵体系域砂体多为细粒砂泥岩,呈孤立状形态;高位体系域砂体以席状砂体为主,主要由滨浅湖、半深湖和湖泊三角洲沉积体系构成。

According to the theory and approach of the sequence Stratigraphy,we have investigated the Paleogene Baoxiangsi formation outcrops in Lanping Basin,and identified four sequence boundaries（one type Ⅰand three typeⅡ）.Sequence stratigraphy framework model and sand body architecture have been illustrated,furthermore,evolutionary model of sequence stratigraphy have been established.Lacustrine level change infuenced heavily on sand body sedimentary structure in Lanping Basin;in early LST river erosion was strong with medium grain texture,and composite sand body developed in late LST.In TST Sand body is generally composed of fine grained mudstone standing in isolation.In HST sand bodies are dominated by those in sheet developed in littoral and shallow lake,bathyal lake and lake delta depositional system.