华北地台西缘晚石炭世一早二叠世早期海水进退及其与聚煤作用的关系

THE RELATIONSHIP BETWEEN THE COAL ACCUMULATING PROCESS AND THE LATE CARBONIFEROUS - EARLY EARLY PERMIAN MARINE TRANSGRESSION - REGRESSION ON THE WESTERN MARGIN OF THE NORTH CHINA PLATFORM

从古元古代至晚古生代,华北地台西缘经历了坳拉槽、槽后坳和坳陷发育阶段.笔者在大区域地层对比及详细的沉积环境分析基础上,对晚古生代海水进退与聚煤作用关系作了较深入研究.结果表明:晚石炭世晚期至早二叠世早期华北地台西缘主要为潮坪和三角洲沉积发育区,在空间上沉积环境具有东西有别南北分带的特点;西部由潟湖潮坪沉积环境逐渐过渡为河控潟湖三角洲和受潮汐影响的河控滨海三角洲沉积环境;东部为潮坪沉积环境,东侧边缘还出现近山滨海平原沉积环境.研究区在晚石炭世早期一早二叠世早期发生过4次2级海水进退,其中第三、第四次海侵全区发育.早二叠世早期初的第三次2级海侵是最大的一次.最大海侵前夕——晚石炭世晚期末是大区域发育厚—巨厚煤层的最好时期.潟湖三角洲平原和陆源碎屑潮上泥炭坪及泥炭沼泽是最佳的聚煤场所.

The aulacogen, post-aulacogen depression and depression took place successively during the Early Proterozoic-Late Palaeozoic in the western margin of the North China Platform.The present paper deals with in detail the relationship between the coal-accumulating process and the Late Palaeozoic marine transgression-regression on the basis of the super-regional stratigraphic correlation and detailed analysis of sedimentary environments. The results of the study show that there were major areas of tidal flat deposition and delta deposition during the late Late Carboniferous-early Early Permian on the western margin of the North China Platform.The sedimentary environments are characterized by difference between the east and west, and by zonation from the north to south in spatial distribution. They changed gradually from lagoonal tidal flat to river controlled lagoonal delta and again to river controlled littoral delta affected by tidal action in the west.The sedimentary environment of tidal flat occurred in the east. The sedimentary environment of near mountain littoral plain also occurred in the eastern margin. Four times of second-order marine transgression-regression occurred during the early Late Carboniferous-early Early Permian in the study area, of which the third and fourth second-order marine transgressions developed all over this area.The third second-order marine transgression occurring at the beginning of early Early Permian marks the maxi-mun transgression period and before its arrival, i. e. at the end of the late Late Carboniferous there was the best developed period of the coal seams in the super-region.The depositional areas of lagoonal delta plain peat swamp, terrigenous supratidal peat flat and terrigenous supratidal peat swamp were the best place of the coal-accumulating process.