NEW KNOWLEDGE ABOUT STRATIGRAPHIC SEQUENCE AND AGE OF THE STRATOTYPE SECTION OF THE NANPIHE FORMATION IN THE LONGBA AREA,GENGMA, SOUTHWEST YUNNAN
DUAN Xiang-dong 1), ZHANG Zhi-bing 1), FENG Qing-lai, 2), WANG Wei 1) LI Zhong-liang 1), YANG Shi-pan 1), and ZHANG Fan 2) ( 1)Regional Geological Institute, Yunnan Bureau of Geology and Mineral Resources, Yuxi,653100; 2)China University of Geosciences, Wuhan, 430074)
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.