内蒙古海拉尔盆地早白垩世含煤岩系层序地层与聚煤规律

摘要

Sequence stratigraphy and coal accumulation pattern of the Early Cretaceous coal measures in Hailar Basin have been studied using outcrop and borehole data in this paper.Based on the regional un-conformity surface,the erosional base of incise valley filled by sandstone and conglomerates,the vertical facies reversal surface and paleontological discontinuous surface,6 third-order sequences were divided in Hailar Basin.Tongbomiao Formation was developed at the initial subsiding stage.Nantun Formation was developed during the rapid subsiding stage.Damoguaihe Formation was formed in the strong extension stage and Yimin Formation was developed during the basin shrinkage stage.The distribution of the Early Creta-ceous coal measures showed best in the eastern and northern,middle part come secondly,and southwest worst.Coal accumulated in the Yimin Formation and the second member of Nantun Formation,where the tectonic subsidence was showing the characters of intermittence,concussion and multi-cyclicity,providing the balance between the increasing rate of accommodation space and the peat accumulating rate favored the accumulation of the regional thick coal seams.%利用煤田钻孔资料，对内蒙古海拉尔盆地下白垩统含煤岩系层序地层格架及聚煤规律进行研究。根据区域不整合面、下切谷砂砾岩体底面、古生物组合突变面及沉积相转换面等层序界面，将海拉尔盆地下白垩统含煤岩系划分为6个三级层序。铜钵庙组是盆地初始断陷阶段的产物；南屯组一段、二段是盆地快速沉降阶段，大磨拐河组一段、二段是盆地稳定拉张阶段，伊敏组是断陷萎缩阶段。盆地早白垩世含煤地层的煤层发育表现为东、北部好，中部次之，西南部差的特点；聚煤作用主要发生在伊敏组及南屯组二段，这2个时期构造沉降表现出间歇性、震荡性及多旋回性，保证了可容空间增加速率与泥炭堆积速率之间的平衡关系，从而形成了区域性的厚煤层。