The Paleohabitat Significance Of Enamel Isotope Composition From Quaternary Mammals In Bubing Basin, Guangxi Province

The reconstruction of the paleoenvironment plays an important role in understanding the origin,extinction and behavior of life.In the Quaternary period,paleoclimate has changed frequently,which consequently caused substantial influence on the paleoenvironment and on the survival of paleontology.Therefore,the reconstruction of palaeoclimate and paleoenvironment is significant for our understanding of the evolution of paleontology.In the Quaternary period,the emergence,widespread distribution and extinction of mammals in southern China,such as Gigantopitheaus,orangutan,small species of giant panda,Homo erectus and Homo sapiens,were closely related to the change of paleoenvironment which they lived in.There are extensive anatomical research of these species,however,limited studies focused on their paleoenvironmental habitat,and their origin and extinction that drived by the environmental changes.In previous studies,researchers used various indicators to reconstruct the paleoenvironment of palaeontology,such as cave sediments,clay minerals,palynology and molecular compounds,which have achieved satisfied results and provided invaluable data for our understanding of the paleoenvironmental context of paleontology and paleoanthropology.However,indicators mentioned in above are indirectly connected with the fossilized bones and are in wide time scale,our analysis using the mammalian enamel isotope collects samples directly from the fossilized teeth,and therefore can reflect the paleoenvironment more intuitively and accurately.The Bubing Basin is located in Tiandong county,Bose city,Guangxi Zhuang Autonomous Region.After years of archaeological investigation and scientific research,abundant fossils from different Quaternary periods have been discovered.Due to the complete chronological sequence,fossils found at the Bubing Basin provide an important reference to establish the evolution and migration of paleontology in South China,and in southeastern Asia as well.Early scientific research at Bubing Basin was based on the morphology of paleontology and chronology of the archaeological sites,and has made significant research achievements in the evolution of ancient humans and mammals.However,limited research on the paleoenvironmental background has impeded our understanding of the origin,evolution and extinction of paleontology in East Asia.Based on the enamel isotope analysis of mammals,and combined with the information from paleontology,chronology and archaeology,this thesis is aiming to reconstruct the paleoenvironment of paleontological localities at the Bubing Basin in different periods,and to discuss the relationship between paleoenvironmental changes and biological evolution.In particular,we focus on the intense changes of habitat(such as extreme weather)and its influence on the paleontological evolution in the key periods.The main conclusions are shown below:Firstly,the reconstruction of Quaternary paleoenvironment through the mammalian teeth enamel isotope indicates that the vegetation at Guangxi was obviously affected by climatic fluctuations,leading to the changes of environment among grassland,forest and the dense forest.Secondly,the reconstructive results of the paleoenvironment by fauna are consistent with the dental enamel isotopes,which show the scientific significance of mammalian tooth enamel isotope for paleoenvironmental reconstruction.Thirdly,the dental enamel isotope analysis shows that the Early Pleistocene Gigantopitheaus fauna experienced two different paleoenvironments during their survival in the Bubing Basin.This has enriched our understanding of the living environment of Gigantopitheaus.Fourthly,the isotopic results of tooth enamel suggest that in the early Late Pleistocene,Homo sapiens in East Asia lived in a relatively warm environment,which is suitable for their survival and development.This strongly refutes the hypothesis that the early Homo sapiens did not exist in East Asia due to the cold climate between 50,000 and 100,000 years ago.Fivethly,multidisciplinary(tooth enamel isotope,mammalian fauna,chronology,etc.)studies on Zhongshan site have shown that although Guangxi is located in the low latitude,paleoenvironment in this region was still affected by extreme climate events(YD events).Meanwhile,humans had the ability to ajust their living stratigies for responding the quick climatic changes.Sixthly,based on the paleoenrivonmental reconstruction of the archaeological sites at the Bubing Basin in different periods,we conclude that the change of paleohabitat environment in the Pleistocene is an important driving force for the evolution of paleobiology in the Bubing Basin.