华北地区石炭—二叠纪下煤组聚煤期岩相古地理

Lithofacies palaeogeography of lower coal group accumulation period of Carboniferous Permian in North China

  • 摘要: 在系统收集钻孔、测井和地质剖面资料以及前人地层、古生物研究成果基础上,对华北地区下煤组进行了横向对比,研究了下煤组分布特征、岩相古地理,及其与奥陶系顶面的空间距离关系。根据太原组野外露头剖面观测及钻孔资料,在下煤组下部地层识别出5种沉积体系。采用单因素分析综合作图法,以下煤组下部地层(时间范围为巴什基尔期—格舍尔期)为作图单元,厘定恢复了下煤组聚煤期岩相古地理。结果表明:华北北部以河流、三角洲沉积为主,承德—兴隆一带发育冲积扇沉积;向南过渡为障壁砂坝—潟湖—潮坪沉积;宁夏以西、辽东半岛、华北中东部以及豫东、皖南以碳酸盐台地沉积为主。以38°N为界,华北地区南北下煤组最有利聚煤环境具有显著差异,该纬度以北厚煤层主要形成于三角洲平原,其次为潟湖—潮坪过渡地带,该纬度以南煤层主要形成于潟湖—潮坪,厚度相对北部较小。对比不同沉积环境以及厚煤层形成机理,总结提出下煤组沉积环境聚煤作用强弱依次为三角洲平原分流间湾、潮坪、潟湖和碳酸盐台地,煤层厚度逐渐变薄,煤层层数增加。对下煤组与奥陶系顶面的空间距离研究表明,下煤组可采区煤层底板距奥陶系顶面的距离一般为10~80 m,南缘下煤组可采区一般在30 m以内;鄂尔多斯盆地北部、冀北—环京津地区和山西河东、太原西山等地为50~80 m;豫东—淮北—鲁西南一带为30~60 m;山东济南—淄博—莱芜一带为30~50 m。

     

    Abstract: Based on the systematic collection of borehole data,logging data and geological profiles as well as previous stratigraphic and palaeontological research results,the authors made a horizontal comparison of the lower coal group in North China,researched its distribution characteristics,lithofacies palaeogeography and spatial distance relationship between the upper surfaces of Ordovician system. According to the survey of field outcrop profiles and borehole data of Taiyuan Formation,the lower stratum of the lower coal group was divided into five sedimentary systems. A single factor analysis and multifactor comprehensive mapping method was applied to recover the palaeogeographic pattern within the lower stratum of lower coal group as an analyzing unit. The results show that in the north of North China,some fluvial and delta deposits are the main sediments,and alluvial fan deposit is developed in Chengde-Xinglong area. Transition to the south is the barrier-lagoon-tidal flat deposits. The carbonate platform deposit is dominant in the west of Ningxia,Liaodong Peninsula,east-central of North China,east of Henan and south of Anhui. With a boundary of 38°N,the most favorable coal accumulation environment of the lower coal group in the North China Basin has significant differences.The thick coal seams in north of 38°N are mainly formed in delta plain,followed by the lagoon-tidal flat transition zones. The coal seam in south of 38°N is mainly formed in the lagoon-tidal flat,with a relatively small thickness. By comparing different sedimentary environments and the formation mechanism of thick coal seams,it is concluded that the coal accumulation strength of lower coal group is in the order of interdistributary bay of delta plain,tidal flat,lagoon,and carbonate platform,and the thickness of coal seams gradually decreases and the number of coal seams increases. The research on the spatial distance between lower coal group and upper surface of Ordovician System shows that the distance in the mineable area is generally about 10-80 m,and the distance in the mineable area of south margin is generally within 30 m. The distance in the northern part of Ordos Basin,the northern part of Hebei,Beijing-Tianjin region,Hedong and Xishan area of Shanxi are about 50-80 m. The distance in eastern Henan-Huaibei-Southwest Shandong are about 30-60 m. And the distance in Jinan-Zibo-Laiwu of Shandong are about 30-50 m.

     

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