Extreme Climate And Sedimentary Response During The Late Triassic Xujiahe Period In The Northern Margin Of The Sichuan Basin

Since the Cambrian bio-radiation,earth has witnessed several biological extinctions.What happened in the history may be the result of our future.Late Triassic is an important turning point during the historical time,which undergoes the third biological extinction.Sichuan basin,located in upper Yangtze platform,record integrated Stratigraphic information.Meanwhile,during that period Sichuan basin also faced active climate fluctuation for the environmental change from marine to continental environment.Therefore,with the help of pervious research,this thesis will take four field sections of late Triassic Xujiahe formation of northern Sichuan basin as research project.With the research of sedimentary facies,Sporopollen data,geochemical characters and charcoal inertinite data,we aim to analyze the extreme climate activities and its sedimentary responses.Results show that,during the late Triassic time,the most common sedimentary environment of research area is braided river delta and alluvial fan.Besides,fern and gymnosperm are the most dominate plants,which made up to the most of its botany characters.Climate research also shows that Xujiahe 5th,7th are the most relatively warm and humid time which are perfect for the coal-forming process.We also identified four times wild fire activities,the three of which are the relatively large-scale wild fire happened at Xujiahe 1st and 5th.Charcoal inertinite data indicates that all the wild fire all ground fire and surface fire,not crown fire found.It is easy to conclude that frequent climate change and extreme climate activities has destroyable impact on coal-forming process.