四川盆地东南部上二叠统龙潭组沉积相新认识  

New Understanding of Sedimentary facies of The Upper Permian Longtan Formation in Southeastern Sichuan Basin,China

作　　者：李昌昊 时志强[1,2] 闫长辉[1,3] 邓虎成[1,3] 田园媛[3] 李瑞雪 LI Changhao;SHI Zhiqiang;YAN Changhui;DENG Hucheng;TIAN Yuanyuan;LI Ruixue(Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China;College of Energy,Chengdu University of Technology,Chengdu,Sichuan 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Erploitation,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [2]成都理工大学沉积地质研究院,四川成都610059 [3]成都理工大学能源学院,四川成都610059

出　　处：《矿物岩石》2024年第4期125-137,共13页Mineralogy and Petrology

摘　　要：近年来在四川盆地关于龙潭组煤层气、页岩气等方面取得较多勘探进展,但关于龙潭组沉积学研究仍较为薄弱。通过对川东南地区两口取心井及9条野外剖面龙潭组沉积岩的野外观察及显微薄片鉴定、扫描电镜观察及微量元素测试等分析,对川东南地区龙潭组沉积相类型、平面分布及演化进行了探讨。综合研究表明,龙潭组煤层主要发育在龙潭组一段和二段时期,煤层多与灰岩呈互层状产出,在灰岩中多见放射虫,海绵骨针等浅海生物。在龙潭组沉积时期,研究区受到海平面频繁变化的显著影响,微量元素测试结果显示龙潭组Sr/Ba值为0.90~3.54,Sr/Cu值为1.34~441.30,V/(V+Ni)值为0.43~0.99,Th/U值为0.09~6.90,以海相沉积为主,整体以缺氧环境为主,潮湿、干热环境交替存在,其中灰岩主要为干热条件下形成。龙潭组底部发育残积相,沉积有喀斯特黏土及角砾;龙潭组一段从东南至北部由泥砂质滨岸逐渐过渡为碳酸盐浅海相;龙潭组二段与一段沉积环境相似,北部为碳酸盐相区,中部、东南部为泥质浅海-滨岸沼泽相区,南、西南部滨岸亚相砂、泥质较为发育;龙潭组三段沉积时期由于海侵加剧,海相范围变大,仅在南部发育有滨岸相区。基于上述因而本次研究认为龙潭组沉积时期研究区主要为海相,而非海陆过渡相,同时基于上述研究以及对海相煤层,推测龙潭组煤层主要沉积于红树林沼泽环境。In recent years,significant progress has been made in the exploration of coalbed methane and shale gas of Longtan Formation in Sichuan Basin.However,the sedimentological research on Longtan Formation remains limited.This paper examines the sedimentary facies types,spatial distribution,and e-volution of the Longtan Formation in southeastern Sichuan through field observations,microscopic thin-section identification,scanning electron microscopy,and trace element analyses on sedimentary rocks from two cored wells and nine cross-sections.The research shows that the coal seams of the Longtan Formation are mainly developed in the first and second members of the formation,often interbedded with limestone rich in shallow marine organisms such as radiolarians and sponge spicules.During the sedimentary period of the Longtan Formation,the study area was significantly affected by frequent changes of sea levels.Trace element analyses show that Sr/Ba values are ranging from 0.90 to 3.54,Sr/Cu values from 1.34 to 441.30,V/(V+Ni)values from 0.43 to 0.99,and Th/U values from 0.09 to 6.90.These values collec-tively indicate a predominantly marine sedimentary environment,characterized by anoxic conditions and al-ternating humid and arid-hot climate phases.The limestone of the Longtan Formation is mainly formed under arid-hot conditions.Residual facies sediments of karst clay and breccia are developed at the bottom of the Longtan Formation.In the study area,from southeast to north,the first member of the Longtan Formation gradually transitions from muddy-sandy shore to carbonate shallow-sea facies.The second member of the Longtan Formation is similar to the sedimentary environment of the first member that a predominance of carbonate facies in the northern region,with muddy,shallow-sea shore-swamp facies in the central and southeastern parts,while in the southern and southwestern parts,the sand and mud of shore subfacies occur.During the sedimentary period of the third member of the Longtan Formation,in-tensified transgression expande

关 键 词：上二叠统 龙潭组 沉积相 微量元素 川东南地区 

分 类 号：P586[天文地球—岩石学] P595[天文地球—地质学]