Visean(carboniferous) Foraminifer Fauna From Guizhou And Guangxi,South China

The Carboniferous Period is one of the most critical transitions in earth history,including the Gondwana superglaciation and the consequent drastic climatic changes,sea-level fluctuations,the rise of new groups and significant biogeographic differentiation.If we want to talk those important geological events,we need an accurate time scale,which make us tale story in the same time.Foraminifers were very abundant,widely distributed,and had high diversities and evolutionary rates in Carboniferous.It has special significance for division of shallow-water facies strata,and the Tournaisian–Visean boundary is defined by the FAD of the benthic foraminifer Eoparastaffella simplex,within the Eoparastaffella ovalis–E.simplex evolutionary lineage.In this thesis,four typical section in Visean Stage of Carboniferous,which are Beian section from Pengchong,Liuzhou,Guangxi Province,Shangsi section from Dushan,Guizhou Province,Yashui A and B sections from Huishui,Guizhou Province,have been studied.Systematic Paleontology and biostratigraphy of foraminifers from these sections have been done.There are lots of foraminifer fossils in the Visean Stage in the Guizhou and Guangxi provinces in South China and the foraminiferal biostratigraphic succession is clear.The Pengchong section in Guangxi has been defined as the Global Boundary Stratotype Section and Point(GSSP)for the base of the Visean Stage.In the Beian section,which is the upper part of Pengchong section,Beian Formation contains abundant and diverse foraminifers,at least 36 genera and 68 species,and they can be divided into five foraminiferal zones,including the Pojarkovella nibelis Zone,Koskinotextularia Zone,Bradyina Zone and Janischewskina Zone in the Visean Stage,and ?Millerella‘ tortula Zone in the Serpukhovian Stage.On the basis of the foraminifers,the Visean–Serpukhovian boundary is placed at the base of the foraminifer ?Millerella‘ tortula Zone in Bei‘an section.Therefore,the Bei‘an section is a reference section for searching GSSP on the base of Serpukhovian boundary.The Yashui section located in Huishui,Guizhou Province is composed by the Yashui A section and Yashui B section and it is a classical section for the Carboniferous stratigraphic study in China.Due to the research on the foraminifer fossils in the Jiusi and Shangsi formations in this section,there are lots of foraminifers,at least include42 genera and 90 species.These foraminiferal can be divided into six foraminiferal zones,including the Paraarchaediscus Zone,Pojarkovella nibelis Zone,Koskinotextularia Zone,Bradyina Zone and Janischewskina Zone in the Visean Stage,and ?Millerella‘ tortula Zone in the Serpukhovian Stage.The Shangsi section,located in Dushan,Guizhou Province,is a typical area for the Carboniferous stratigraphic study in China.In this work,the author first studied the foraminifers in the Jiusi Formation and the lower part of the Shangsi Formation in this section.It is discovered that there are lots of foraminiferal fossils in this section and that they can be divided into four foraminiferal zones,which are,in ascending order,the Paraarchaediscus Zone,Pojarkovella nibelis-Koskinotextularia Zone,Bradyina Zone and Janischewskina Zone in the Visean Stage.By summarizing the work from this study and others,seven foraminiferal zones in the Visean Stage of the Carboniferous in South China have been recognized,which are,from the bottom to the top,the Eoparastaffella simplex Zone,Viseidiscus/Planoarchaediscus Zone,Paraarchaediscus Zone,Pojarkovella nibelis Zone,Koskinotextularia Zone,Bradyina Zone and Janischewskina Zone.This work has established and perfected the foraminiferal biostratigraphic succession in Visean Stage of Carboniferous in South China and provided a reasonable biostratigraphic framework for the stratigraphic division and correlation.The Shansian Stage,which is a regional chronostratigraphic unit in Carboniferous of China,is originated from the Shangsi Formation.The research on foraminifer fossils from the Shangsi Formation in the Yashui and Shangsi sections indicates that the base boundary of Shangsian is roughly equivalent to the base boundary of Bradyina Zone,which is roughly equivalent to the base boundary of MFZ 14–Howchinia bradyana Zone in Western Europe and Eostaffella proikensis Subzone in Russia.Therefore,the Shansian is roughly equivalent to the middle and upper part of Warnantian Stage in Western Europe,the Aleksinian,Mikhailovian and Venevian substages in Russia,and the upper part of Global Visean Stage.This work provides a reasonable foraminiferal evidence for the international correlation of Shansian Stage.The author described a large number of foraminiferal fossils from Guizhou and Guangxi provinces in South China.A new species has been discovered and named as Howchinia beianensis sp.nov.This study has shown that the stratigraphic range of the genus Howchinia is from the late Visean to early Bashkirian in South China.Howchinia species occupied both shallow-water and relatively deep-water environments.They make an effective link for biostratigraphic correlations between in shallow-water and deep-water sections.The research on foraminiferal fossils from South China in this work can better reflect the real foraminiferal world in South China and even in the world during the period of Visean in Carboniferous.