豫西登封煤田马岭山一带山西组沉积环境及二_1煤层厚度变化因素分析

登封煤田马岭山一带,山西组地层是发育在总体海退阶段,以过渡相为主的含煤沉积。据岩性、岩相和旋回结构的研究,首次将山西组地层划分出四个段,并对“老君堂砂岩”和“冯家沟砂岩”提出了命名。据古生物学、矿物学、地球化学、岩石学、古水流、砂岩体及煤层相的研究,用环境参数及相模式法,首次对山西组含煤岩系沉积环境进行系统研究,划分出33个微相,归属为四个垂直相序及泻湖—潮坪—障壁岛和滨海三角洲两大沉积体系。首次在灰岩燧石层、硅质泥层中发现了海绵岩。据沉积环境和聚煤期古构造的研究,初步得出二_1煤厚变化地质因素主要是沉积环境及聚煤期基底差异沉降,其次为河流冲蚀作用及后期构造影响的结论。通过岩相一厚度法或相一厚度分析,初步认为研究区中部隆起区主要为3.5米以下的薄煤带,而大于8米的巨厚煤带则集中分布于研究区东西两侧坳陷区。

An Analysis of the Sedimentary Environment of Shanxi Formation at Deng-feng Coal Field,West Henan and the Factors Influenced the Thickness of Coal Seam Ⅱ1

The Shanxi formation in the Maling-shan of Dengfeng coal field, Henan shows its development as a deposite of coal bearing sedimentation dominated by transitional phase during the period of marine regression. According to the lithofacies,the lithological characters and the cy- cles of sedimentation,Shanxi formation is separated into four groups and the corresponding strata,Laojuintang sandstone and Fongjiagou sandstone ard now nominated. By means of mineralogy,lithology,palaeontology,geochemistry and palaeocurrent analysis,facies of sandstone and the coal measures of Shan- xi formation,we come to the conclusion that they are divided into 33 microfacies,four vertical facies sequence and finally into two big depositional systems,i.e.the coastal delta system and the lagoon-wadd barrier-island system.Besides,we found spongilite associated with bra- chiopods in chert limestone or silicious mudstone of coal measure stra- ta.They are much helpful in identifying the sedimentary environment, and as far as we can see they had not been found before in this district. By the research of the regional sedimentary environment and palaeo- structure of coal forming period,we are persuaded that the thickness variationof coal seam Ⅱ_1 was cheafly due to the local sedimentary environ- ment,the differential subsidence of basement and the river erosion,while the tectonic influence in succession played only a minor part. By the analysis of lithofacies-thickness or facies-thickness we con- fessed initially that in the uplift area of this region,coal less than 3.5 meters thick can only be expected,but we can get thick coal of above 8 meters in the depression area in the east and west part of the coal field.