摘要
沉积环境分析是古地理重建的核心内容,黔北地区寒武系明心寺组沉积环境研究存在较大争议,以致对中上扬子地区明心寺组沉积期古地理格局的认识不能统一。选取寒武系明心寺组发育齐全、出露良好的黔北镇远地区三丘田剖面为研究对象,通过野外剖面观察、室内薄片鉴定及碎屑岩粒度分析等方法对三丘田剖面明心寺组岩石学特征、沉积构造、沉积演化序列、沉积相类型进行了详细分析。结果表明:黔北镇远地区三丘田剖面寒武系明心寺组上段发育大套的石英粉-细砂岩,沉积构造以低角度冲洗交错层理为主,碎屑颗粒的成分和结构成熟度均较高;三丘田剖面明心寺组上段砂岩以双次跳跃组分为主,悬浮组分含量较少,纵向剖面自下而上显示为浅水陆棚→临滨→前滨→后滨演化序列,呈典型的陆棚相向滨岸相变化。综上所述,黔北镇远地区三丘田剖面寒武系明心寺组上段的沉积相为滨岸相。黔北镇远地区明心寺组滨岸相沉积的出现,指示了黔北地区区域上重新认识明心寺组沉积相的必要性,将直接影响对黔北地区乃至中上扬子地区寒武纪古地理格局及其大地构造背景的认识。
The analysis of depositional environment is the core content of paleogeographic reconstruction.There is greet disputes on the study of the sedimentary environment of Cambrian Mingxinsi Formation in the northern Guizhou,which leads to the different opinions on understanding of paleogeographic pattern of the middle-upper Yangtze region during Mingxinsi Formation sedimentary period.The succession of Cambrian Mingxinsi Formation from the well-developed Sanqiutian Profile in Zhenyuan area,the northern Guizhou was measured,and the lithological characteristics,sedimentary structure,sedimentary evolution sequence and sedimentary facies types of Mingxinsi Formation in Sanqiutian profile were analyzed in detail by outcrop observation,thin section identification and particle size analysis of clastic rocks.The results show that Cambrian upper Mingxinsi Formation in Sanqiutian profile of Zhenyuan area,the northern Guizhou develops a large set of quartz silty-fine sandstone,the sedimentary structure is dominated by low-angle washing cross-bedding,and the clastic particle is well sorted and rounded;the sandstones of upper Mingxinsi Formation in Sanqiutian profile are mainly composed of double jump components with a small amount of suspended components,and the vertical profile sequence shows a typical variation of shelf facies to shore facies,and the evolution sequence from bottom to up is shallow shelf→shoreface→foreshore→backshore.In conclusion,the sedimentary facies of Cambrian upper Mingxinsi Formation in Sanqiutian profile of Zhenyuan area,the northern Guizhou belongs to shore facies.The appearance of shore facies deposit in Zhenyuan area indicates the necessity of re-understanding the sedimentary facies of Mingxinsi Formation in the northern Guizhou,which will directly affect the understanding of Cambrian paleogeographic pattern and geotectonic background in the northern Guizhou and even the middle-upper Yangtze region.
作者
王萌
牟传龙
梁薇
郑斌嵩
侯乾
WANG Meng;MOU Chuan-long;LIANG Wei;ZHENG Bin-song;HOU Qian(College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,Shandong,China;Chengdu Center,China Geological Survey,Chengdu 610081,Sichuan,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,Hubei,China)
出处
《地球科学与环境学报》
CAS
北大核心
2020年第1期120-131,共12页
Journal of Earth Sciences and Environment
基金
中国地质调查局地质调查项目(12120115004301)
关键词
岩相古地理
明心寺组
粒度分析
沉积构造
冲洗交错层理
滨岸相
陆棚相
贵州
lithofacies paleogeography
Mingxinsi Formation
particle size analysis
sedimentary structure
washing cross-bedding
shore facies
shelf facies
Guizhou
