梅河盆地古近系梅河组沉积层序演化特征

Sedimentary and sequence evolution of Paleogene Meihe Formation in Meihe Basin

梅河盆地为典型的断陷型含煤、油页岩盆地。通过岩芯、测井和地震的层序标志识别,在梅河盆地梅河组识别出1个巨层序、2个超层序和4个三级层序。其中,砂砾岩段、下部含煤段、中部泥岩段、上部含煤段分别对应着三级层序I、II、III和IV。通过对层序地层格架的认识,结合构造、沉积分析,揭示了研究区梅河组沉积层序演化规律,三级层序地层格架内沉积演化分别为:层序I发育了盆地初始裂陷阶段的冲积型和扇三角洲沉积;层序II发育了盆地裂陷扩张阶段扇三角洲、沼泽和浅水湖泊沉积;层序III发育了盆地最大扩张阶段深水湖泊沉积;层序IV发育了盆地萎缩阶段扇三角洲和湖泊沉积。因此,梅河盆地梅河组的层序I到层序IV的演化揭示了中国东部伸展环境下断陷盆地从初始裂陷阶段到盆地萎缩阶段完整的不同沉积层序演化特征。

Meihe basin is a typical fault depression basin with coal and oil shale. The Meihe Formation is divided into 1 megasequence,2 supersequences and 4 three-order sequences by utilizing core,well logging and seismic data. Among those three-order sequences,sequence I is conglomerate member,sequence II is lower coal member,sequence III is mudstone member and sequence IV is upper coal member. The sequence stratigraphic framework and sedimentary-tectonic analysis reveal the sedimentary sequence evolution regularity of Meihe Formation in the studied area. Sedimentary and sequence evolution in Meihe Basin show that sequence I was the initial faulting stage of the basin,dominated by coarse clastic sediments of alluvial fan and fan delta. Sequence II was the faultingexpansion stage of the basin,with more developed sediments of fan delta swamp and lacustrine. Sequence III was the largest expansion stage of the basin,dominated by mudstone of deep lacustrine facies deposits. Sequence IV was the shrinking stage of the basin,dominated by sediments of fan delta and lacustrine. So the sequence evolution from sequence I to sequence IV disclosed the typical and complete sedimentary-tectonic evolution of the eastern extension conditions from the initial faulting stage to shrinking stage.