滇西南耿马弄巴地区南皮河组层型剖面地层层序、时代的重新认识

对前人建立的上二叠统南皮河组的层型剖面——弄巴剖面进行了详细研究 ,发现该地层属于一套被动大陆边缘浊积岩为主的沉积岩系 ,可概括为四种层序类型特征 :一为代表浊流沉积的鲍马序列 ;二为由泥质岩与岩屑石英 (杂 )砂岩透镜体 (层 )构成的水道沉积序列 ;三为由薄层状砂岩与泥岩呈韵律状互层构成的浊流远端低密度流序列 ;四为薄层状硅质岩与硅质泥岩呈韵律状组成的基本层序。该组中采获了低等蕨类植物、牙形石和笔石等化石 ,证实其时代属于早泥盆世—晚泥盆世。根据该地层的岩性组合、沉积环境等特征及区域对比 ,应归于泥盆系温泉组。

NEW KNOWLEDGE ABOUT STRATIGRAPHIC SEQUENCE AND AGE OF THE STRATOTYPE SECTION OF THE NANPIHE FORMATION IN THE LONGBA AREA,GENGMA, SOUTHWEST YUNNAN

The Nanpihe Formation was formerly considered as Late Permian in age. Recently, the named section of this formation has been carefully researched in regional geological surveying and four types of sedimentary sequences were found: first is the Bouma sequence representing turbidity current deposit; second is channel depositional sequence consisting of mudstone and lens-shaped lithic quatz sandstone or gray wake; third is low-density turbidity sequence composed of flaggy sandstone and mudstone;and fourth sequence is a rhythemic intedbed composed of thin-bedded siliceous rock and siliceous mudstone. We suggest that the strata are turbidite sequences that are deposisted on the passive continental margin. The strata containing plant, conodont and graptolite belongs to Early—Late Devonian. According to the lithological association, sedimentary environment and regional stratigraphic correlation, it should be the Devonian Wenquan Formation.