Taphonomy And Geo-protection Of Dinosaur Fossils In Yunyang,Chongqing

A new Dinosaur fauna is discovered in Puan,Yunyang,Chongqing,China.It is a remarkable discovery after Dashanpu Shunosaurus fauna in Zigong,Sichuan.The fossils are exposed from the Middle Jurassic Xintiangou Formation and Lower Shaximiao Formation respectively,which are characterized by the amount of quantity and species.After years of excavation,nearly ten thousand pieces of various fossil specimens have been collected,and a single dinosaur fossil excavation site of Jurassic original site with the length of about 150 m and the height of 6 ～ 10 m has been preserved in the Lower Shaximiao Formation.The discovery of the dinosaur fauna provides a large number of new fossil materials for the study of the evolution of dinosaurs in the Middle Jurassic period,and also enriches the types of geological relics in Chongqing,and provides realistic materials for paleontological popular science education activities.Although many new genera and species of dinosaurs have been named in the study area in terms of dinosaur morphology,the research results on taphonomy are still scattered and lack of systematic discussion.At the same time,the area has not been explored from the perspective of geological relics protection.Consequently,the dinosaurs’ fossil burial sites were selected as the target of investigation.Based on the field investigation and the pre-existing data and previous research results,the study of sedimentary environment,paleoclimatic characteristics and burial time of dinosaur fauna were carried out by the theories of sedimentology,paleontology,geochemistry and taphonomy.Based on the above research,the burial mechanism of fauna is discussed.Meanwhile,combined with the characteristics of the environment and the present situation of fossils protection,the protection of geoheritage is discussed.The main results and conclusion of this thesis are as follows:(1)By analyzing the lithofacies,sedimentary structure,paleontology,and fine-grained clastic rock geochemical characteristics of the Middle Jurassic Xintiangou Formation and Shaximiao Formation in the study area,it is considered that the Xintiangou Formation in the area was deposited in the delta environment,and the burial environment of those fossils in Xintiangou Formation is the delta front.The sedimentary stage of the Shaximiao Formation is dominated by the river environment and has experienced a short lacustrine sedimentary environment.The burial environment of the fossils from Lower Shaximiao Formation is a floodplain.The period of Xintiangou Formation in the study area is dominated by a warm and humid climate,with fluctuations of drought and humidity,while the sedimentary period of the Shaximiao Formation is dominated by an arid climate.(2)The comprehensive analysis of zircon U-Pb geochronology data in the area shows that the Xintiangou Formation was deposited in the Early Aalenian and the fossil burial time is about 174 Ma.The Shaximiao Formation was deposited in the Bajocian-Bathonian and the fossil burial time is between 169 and 166 Ma.According to the zircon U-Pb geochronology data,the burial time of the dinosaur fauna in the study area is earlier than that of the Shunosaurus-Omeisaurus Fauna.(3)The dinosaur fossils in the Xintiangou Formation have poor correlation as a whole,most of them are scattered,and their burial environment is different from the commonly recognized dinosaur habitat.Therefore,the remains of dinosaurs may have undergone a certain distance of transportation after death.It is speculated that the centralized burial of fossils in the Xintiangou Formation may be related to the rapid bury by sand and mud in the delta front after their death.A large number of soft-sediment deformation structures and metha-derived tubular calcareous nodules developed in the Lower Shaximiao Formation may be the geological records of mud volcano in the area during this period.We speculated that the centralized burial of fossils in the Lower Shaximiao Formation may be related to this geological process.(4)The paleontological heritage in the study area is represented by dinosaur fossils,with rich types,wide distribution,and a large number.According to the comparative analysis,the abundant paleontological heritage in the area can provide materials for dinosaur evolution and dinosaur fossils taphonomy research,which is of great scientific research value.At the same time,from the perspective of resource endowments,the rich paleontological heritage resources in the area are very shocking and attractive and have high science popularization value and development value.(5)Yunyang County is located in the hinterland of the Three Gorges Reservoir Region and natural disaster occurs frequently.Geological disaster investigation and GIS spatial analysis show that there are a large number of potential landslide disasters in and around the proposed Dinosaur National Geopark,and the paleontological heritage in the study area suffers a great risk of natural damage.Based on the analysis of the practice of paleontological heritage protection,the improvement approach is needed in the study area can be raised from the weak links of the existing paleontological heritage protection measures,involving improving the prevention of natural disasters,the construction and management of rules and regulations,and the protection fund-raising channels,etc.