济阳坳陷古近系孔店组高频韵律旋回沉积记录及成因

摘要

济阳坳陷古近系孔店组发育一套紫红色泥岩、灰色粉砂岩以及膏质泥岩等岩相组合的高频韵律旋回沉积。利用测井资料、录井剖面、岩心观察以及为地球化学元素等手段，对济阳坳陷古近系孔店组高频韵律旋回沉积机制进行了深入研究。结果表明，济阳坳陷孔店组旋回沉积记录包括颜色米级旋回、粒序米级旋回和非粒序米级旋回；发育6种岩相组合类型及23种岩相组合，共划分出276个米级旋回，旋回最大厚度为29.6 m，最小厚度为1.48 m，平均厚度为6.28 m；利用Fisher图解和测井曲线频谱分析，得出岁差周期为19.2～23.4 ka，斜率周期为39.1～51.4 ka，偏心率主要周期95.3～403.1 ka。该差值与古近纪超短期旋回、短期旋回和中期旋回的时间差基本一致，证实了孔店组湖泊相旋回沉积受控于米兰科维奇旋回。除此之外，旋回发育时期的古气候、沉积水介质的共轭震荡、物质供应等沉积动力因素也影响了旋回的发育过程。最后，建立了济阳坳陷古近系孔店组低水位干旱时期和高水位潮湿时期的旋回沉积动力模型，探讨了米兰科维奇旋回控制下旋回沉积的原始沉积动力和古环境面貌。%There is a set of high frequency cycles with lithological combination of purple red mudstone ,grey siltstone and gypsiferous mudstone developing in the Kongdian Formation of Jiyang Depression .By using logging data ,well logging ,core observation and elemental geochemistry methods ,this paper researched the deposition mechanism of high frequency cycles of the Kongdian Formation in Jiyang Depression .The research results show that the cyclic sedimentation record of Kongdian Formation in Jiyang Depression consist of color meter scale cycle ,graded meter scale cycle ,non-graded meter scale cycle and consist of 6 types of lithofacies assemblages which include 23 kinds of lithology combinations .The cyclic sedimentation record can be divided into 276 cycles,with the maximum thickness being 29.6m,the minimum thickness being 1.48m,and average thickness being 6.28m.Fisher diagrams and the spectrum analysis of logging curves reveal that the precession cycle is 19.2-23.4 ka,slope cycle is 39.1-51.4 ka,and eccentricity cycles is 95.3-403.1 ka.They are consistent with the period of ultra short term cycles ,short-term cycle and medium-term cycles,respectively.So it is confirmed that the cyclic sedimentation record was controlled by the Milankovich cycle .In addition,it was also influenced by paleo-climate,sedimen-tary medium conjugate concussion and material supply .Finally,the cyclic-sedimentation dynamic model during low /high-stand period of Kongdian Formation in Jiyang Depression is established ,and the original sedimentary dynamics and ancient environment of the cyclic sedimentation record under the control of Milankovich cycle are discussed .