Jurassic Global Climatic Paleogeographic Evolution And Its Implications For Dinosaur Fossil Distribution

The Jurassic was a typical period of greenhouse climate,with higher CO₂ content,higher temperature,and less precipitation,which differed greatly from modern climate.In recent years,the global climate has continued to rise,and we believe that the Earth is likely to enter the greenhouse period in the near future.In order to enhance the understanding of the Jurassic climate,the relationship between major terrestrial vertebrates and the environment,scientists have sought out typical examples of deep time periods.The Jurassic is one of these alternatives.The Jurassic was the time when dinosaurs began to dominate the land,and it is traditionally believed that the warm and ?? Jurassic climate was beneficial to the rapid ecological occupation of dinosaur niches.However,there is growing evidence that the Jurassic climate was unstable,with many major geological events associated with climate and environmental change occurring during this time,such as the Toarcian Oceanic Anoxic Event(T-OAE)of the Early Jurassic,Central Atlantic igneous province activity(CAMP),continued global sea level rise,and some regional storm events.Various geological events have global or local impacts on the global Jurassic climate,and systematic and quantitative studies of the Jurassic climate are lacking.In addition,the relationship between dinosaur fossil preservation and climate is mostly described by local qualitative indicators,mostly in terms of arid or semi-arid climatic features,and quantitative and systematic regularity studies of both are lacking.In this paper,based on quantitative paleoclimatic parameters obtained from geological indicators and paleoclimate simulations,two-time sections of the late Early to Middle Jurassic(?180 Ma)and early Late Jurassic(?160 Ma)climatic zones were delineated and validated using climate-sensitive sediments.The results show a good correspondence between the two,and the accuracy of the climatic zones delineated by the large number of paleoclimates indicative of these geological indicators is high.Further quantitative climate pointer(paleoclimate simulation)analysis results show that the Jurassic mean annual temperature was approximately 19?,approximately 4? higher than the modern global mean annual temperature(14.9?),with a warm climate signature.Integrating climate-sensitive sediment data and using Arc GIS spatial analysis,the spatial distribution of global dinosaur fossils was compared with that of climate-sensitive sediments in the Jurassic period.The quantitative results showed that there were strong differences in the distribution patterns of global Jurassic dinosaur fossil sites,with about 80% of dinosaur fossils distributed in the arid zone in both the Early-Middle and Late Jurassic,and mainly in Tropical Desert climate zone;under the Jurassic climatic zone of the paleoclimate simulation,the same pattern of favourable preservation of dinosaur fossils in the arid zone is confirmed,with the preservation proportion remaining at nearly 80%.To further validate this understanding,the Lufeng Basin,which is rich in dinosaur fossils from the Early Jurassic,was selected for oxygen and carbon isotope studies of apatites.The results showed that the mean annual temperature(MAT)of the Early Jurassic was 21±3?and the mean annual precipitation(MAP)was 965±460mm,which concluded that the area had a Savanna climate.The savanna climate indicates that Lufeng County had distinct wet and dry seasons in the Early Jurassic.This conclusion is consistent with the inference that dinosaur fossils have a strong preference for arid regions.The distinct wet and dry savanna climate is not only conducive to the living and reproduction of dinosaurs,but also to the preservation of dinosaur fossils,which is the reason for the homeland of Lufeng dinosaurs.