宽浅型湖盆层序地层学研究:以塔里木盆地古近系为例

Study of sequence stratigraphy developed in wide-shallow lake: An example from Tarim basin in Paleogene

基于塔里木盆地古近系虽然沉积厚度较小,但沉积相类型丰富(包括河流相、湖泊相、三角洲相、冲积扇相和碳酸盐岩台地相等),综合野外露头资料、测井资料以及地震资料进行分析。研究结果表明:古近系可识别出5个层序界面,划分出4个三级层序;除第1层序分布较局限外,其他层序在塔里木盆地均有分布;塔里木盆地古近系层序的分布特征受到古地貌的控制,塔里木盆地内部地势相对平坦,沉积期水体浅;宽浅型湖盆层序内部以低位体系域和湖侵体系域为主,局部发育高位体系域;在盆地边缘的坳陷区,各层序体系域发育齐全,沉积厚度较大;与一般陆相三级层序不同的是,宽浅型湖泊层序低位体系域最发育,湖侵体系域沉积厚度小,且沉积物粒度细,高位体系域发育不全,多被剥蚀。

The thickness of Paleogene is small in Tarim basin,but sedimentary types including fluvial,lake,delta and alluvial fan are abundant.Based on outcrops,logging data and seismic data,5 sequence boundaries and 4 third-order sequences were recognized in Paleogene in Tarim basin.The results show that sequences distribute all over the Tarim basin,except the first sequence distributed locally.The distribution feature is controlled by paleogeomorphic and the terrain in Tarim basin is flatter relatively.The body of lake is shallow and clear in Tarim basin.The sequences develop lowstand system tract and trangressive system tract well in Tarim basin,and highstand system tract presents locally in Tarim basin.The sequences developing on margin of Tarim basin develop fully,and deposition thickness is high.The sequences developing in wide-shallow lake have features that are different from other types sequences developing in continental.The low system tract develops best among three system tracts,and thickness of trangressive system tract is smaller and grain is finer.The high stand system tract does not present well because of the erosion.