山西沁水盆地东南部上石炭统—下二叠统太原组聚煤环境

Coal-accumulating environments of the Upper Carboniferous-Lower Permian Taiyuan Formation in southeastern Qinshui Basin,Shanxi Province

山西沁水盆地上石炭统—下二叠统太原组含有重要的可采煤层和煤层气资源,并在该盆地东南部陵川县附城镇一带出露良好露头。基于对太原组露头剖面和部分钻孔资料的研究,综合分析了该组的岩性、沉积构造、实体化石、遗迹化石和沉积序列等沉积特征。(1)太原组灰岩形成于正常浅海(开阔台地)和局限海湾(局限台地)2种沉积环境,其中,L1灰岩顶部、L2灰岩中下部、L4灰岩上部、L5灰岩顶部、L7灰岩顶部和L8灰岩形成于局限海湾环境,其他灰岩层均形成于正常浅海环境;(2)根据太原组煤系岩性组合特征,划分出6个岩性段,各段中的碎屑岩及所含煤层形成于障壁岛(砂岛)、潟湖和潮坪环境中;(3)通过对沉积特征和沉积序列的分析,识别出11种沉积序列类型,提出了太原组煤系发育的岛湖潮坪、局限海湾(潟湖)潮坪和滨岸潮坪等3种聚煤环境模式。该成果可为沁水盆地东南部太原组煤及煤层气勘探与开发提供沉积背景方面的重要信息和理论支撑。

The Upper Carboniferous -Lower Permian Taiyuan Formation in Qinshui Basin contains important mineable coal seams and coalbed methane resources,and is well exposed in Fucheng town of Lingchuan County in southeastern Qinshui Basin,Shanxi Province.Based on the outcrop section observa_tion and a part of borehole data of the Taiyuan Formation,the paper synthetically analyzed the lithologicfeatures,sedimentary structures,body fossils,trace fossils,sedimentary sequence and some other depo_sitional characteristics.（1 ） Carbonate rocks of the Taiyuan Formation in this area were formed in two sed_imentary environments, i.e., open shallow sea （open platform） and restricted bay （restricted plat_form）,among which,the top of Limestone 1 （L1 ）,middle_lower part of L2 ,the upper part of L4 ,thetop of L5 ,the top of L7 and the L8 were formed in a restricted bay environment,and other limestone bedswere generated in an open shallow sea environment; （2） Based on the lithologic association characteris_tics of the Taiyuan Formation coal measures in the study area,six lithologic members were classified,andclastic rocks and coal seams in each member mainly were formed in sedimentary environments includingbarrier island （sand island）,lagoon and tidal flat; （3） After analyzing sedimentary characteristics andsedimentary sequence,1 1 types of sedimentary sequences were distinguished and 3 types of coal_accumu_lating environment modes were proposed in the Taiyuan Formation coal measures of this area,includingcoal_accumulating environment of tidal flat associated with barrier island and lagoon depositional system,the coal_accumulating environment of tidal flat alongside restricted bay （lagoon）,and the coal_accumula_ting environment of coastal tidal flat.The results may provide important information and theoretical supportsof sedimentary background for coal and coalbed methane exploration and developing in the Taiyuan Forma_tion of southeastern Qinshui Basin.