CAJ | 학술논문

晚三叠世为中国南方重要的聚煤期，盐源地区晚三叠世含煤地层主要为博大组和冬瓜岭组。根据野外露头、探槽及岩心资料的沉积学研究，博大组沉积期由于北部长枪-琪木林岛链的障壁作用，主要发育滨岸潮坪沉积，以陆源碎屑岩夹泥质、砂质碳酸盐岩为主，物源区为东南部的康滇古陆，成煤环境为潮坪沼泽；冬瓜岭组沉积期由于大规模海退并伴随周围古陆快速抬升，盆地沉积以河流-三角洲相的碎屑岩为主，成煤环境以分流间湾沼泽为主。构造不整合面在盐源地区广泛存在，表现为博大组与舍木笼组之间、冬瓜岭组与博大组之间的平行不整合面；下切谷砂体底部河流侵蚀不整合面在冬瓜岭组广泛发育，三段、六段底部均见河床底部滞留沉积的粗砂、砾岩。本次研究主要根据区域性构造不整合面、河流侵蚀不整合面及河道砂体的发育特征等，建立了盐源地区晚三叠世层序地层格架，在盐源地区晚三叠世煤系中识别出5个层序界面，共划分为4个三级层序(层序 I-IV)。其中层序 I对应博大组；层序 II对应冬瓜岭组一段和二段；层序 III对应冬瓜岭组三段、四段和五段；层序IV对应冬瓜岭组六段、七段和八段。这些层序中，聚煤作用以层序II最强，其次为层序III；在层序内部，又以湖(海)侵体系域聚煤最好，高位体系域次之。
만삼첩세위중국남방중요적취매기，염원지구만삼첩세함매지층주요위박대조화동과령조。근거야외로두、탐조급암심자료적침적학연구，박대조침적기유우북부장창-기목림도련적장벽작용，주요발육빈안조평침적，이륙원쇄설암협니질、사질탄산염암위주，물원구위동남부적강전고륙，성매배경위조평소택；동과령조침적기유우대규모해퇴병반수주위고륙쾌속태승，분지침적이하류-삼각주상적쇄설암위주，성매배경이분류간만소택위주。구조불정합면재염원지구엄범존재，표현위박대조여사목롱조지간、동과령조여박대조지간적평행불정합면；하절곡사체저부하류침식불정합면재동과령조엄범발육，삼단、륙단저부균견하상저부체류침적적조사、력암。본차연구주요근거구역성구조불정합면、하류침식불정합면급하도사체적발육특정등，건립료염원지구만삼첩세층서지층격가，재염원지구만삼첩세매계중식별출5개층서계면，공화분위4개삼급층서(층서 I-IV)。기중층서 I대응박대조；층서 II대응동과령조일단화이단；층서 III대응동과령조삼단、사단화오단；층서IV대응동과령조륙단、칠단화팔단。저사층서중，취매작용이층서II최강，기차위층서III；재층서내부，우이호(해)침체계역취매최호，고위체계역차지。
Late Triassic is one of the most important coal-accumulating periods in South China, and Boda and Dong-gualing Formations of Late Triassic are coal-bearing strata in Yanyuan area. Boda Formation was developed in the tidal flat environment associated with the barrier of Changqiang-Qimulin Islands, and the Formation mainly consists of clastic rocks interbedded with muddy and sandy limestone, with a provenance from Kangdian Mountains to the southeast. The coal-forming swamp was developed from the coastal tidal flat environments. Donggualing Formation was formed in the fluvial plain to lacustrine delta environments developed as a result of regression and rapid uplift of the surrounding mountains. The coal-forming swamp at this stage was developed from the delta plain inter-distributary bay and fluvial flood basin environments. Tectonic unconformities were widely distributed in Yanyuan area, including the parallel unconformities between Boda and underlying Shemulong Formations, and between Boda and Donggualing Formations. Erosional surfaces at the base of incised valley channel sand bodies were developed in Donggualing Forma-tion, especially in Members 3 and 6. According to these key surfaces, totally 5 sequence boundaries were identified and 4 third-order sequences were subdivided in the Late Triassic coal-bearing strata. Sequence 1 corresponds to Boda Forma-tion, Sequence 2 corresponds to Members 1 and 2 of Donggualing Formation, Sequence 3 corresponds to Members 3, 4 and 5 of Donggualing Formation, and Sequence 4 corresponds to Members 6, 7 and 8 of Donggualing Formation. Coal accumulation was favored in sequence II, followed by sequence III, while within these sequences, coals were preferen-tially accumulated in the transgressive systems tract, and then the highstand system tract.