Taphonomic Analysis Of Dinosaur Footprints And Fossils Of Lower Jurassic Lufeng Formation In Lufeng,Yunnan

Lufeng Dinosaur National Geopark,Yunnan is located in Lufeng county in Chuxiong Yi Autonomous Prefecture in Yunnan province,which is one of China's famous localities of Jurassic dinosaur fossils.Based on the summary of previous studies and the field geological survey,this paper carries out particle size distribution analysis,with the lithological,mineralogical,sedimentary,and paleontological features,the sedimentary environments of the strata in Early Jurassic are determined.Moreover,taphonomic analysis is made for dinosaur footprints and skeletons in terms of sedimentary facies,fossil distribution,transformation and accumulation characters,and fossil microstructures,and the taphonomic features of dinosaur footprints and skeletons are described.The dinosaur living and buried environments and buried-fossilized mode of dinosaur fossils are proposed.The major results of this paper are as follows: the dinosaur footprint-bearing strata in Dalishu indicate an arid lake in Early Jurassic.Affected by periodic precipitation,the environment alternated between the shore and shallow lake,resulting multiple sedimentary cycles.Dinosaur skeleton-bearing horizons show the characteristics of lecee and flooding plain of meandering river.Dinosaur skeletons are lower in diversity,locally enriched and mixed accumulation,dominated by vertebrae,cervical rib,ribs and phalanges,the fossil bones are generally less than 1m long,the most of which less than 0.4m.There are some cracks on the bone surface,wore on epiphyseal and partial dislocation,without biological damage,which reflect social habits of dinosaurs,and bodies are transported by river and buried in other place shortly after their death(with a short-term exposure).The bone fossils are mainly composed of biogenic apatite,non-biogenic calcite and iron oxides.Calcite and iron oxide crystallized,filled and replaced apatite in the limited space,forming two different patterns in the cancellous bone of epiphyseal and the canal of Havers tube.Large-scale micro-cracks in the cortical bone near the Havers canal inner wall show that the climate was extreme arid before bones were buried.The burial-fossilized model of dinosaur bones from Lufeng formation of Lower Jurassic can be summarized as extremely arid habitat-massive dinosaurs death-body decay-transported by river in heavy rains season and finally deposited-fast burial-Fossilization(Diagenesis)-exposure and excavation.Lufeng area in the Chuxiong basin was greatly affected by Ailaoshan orogeny and associated volcanic activity in the Early Jurassic,the extremely arid climate was closely related to the regional geological setting.