滇中楚雄盆地上侏罗统妥甸组生物化石的发现及古环境意义OA

Objectives:During the Late Jurassic,the Chuxiong Basin in central Yunnan served as a typical inland lake,where a thick succession of red clastic sedimentary rocks—commonly known as"red beds"—was deposited.Based on a 1:50000-scale regional geological survey,a unique fossil assemblage comprising dinosaurs,turtles,fish,bivalves,and plants was discovered for the first time within the Upper Jurassic Tuodian Formation in the Shuangbai area of the Chuxiong Basin. Results:The fossils are well-preserved and occur in situ.The host lithology consists of purplish-red fine-grained lithic sandstone and silty mudstone.Research has identified the dinosaur remains as theropods,the turtle fossils as Xinjiangaspideretes oshansis,the fish as Lepidotes,the bivalves as Plicatounio,and the plant fossils as Amentotaxus.Additionally,fossil fragments of other unidentified vertebrates were also recovered.This significant discovery not only enhances our understanding of Late Jurassic biodiversity in the Chuxiong Basin but also fills a critical gap in the vertebrate fossil record of the basin's Late Jurassic strata.Considering the composition of the fossil assemblage and associated sedimentary structures such as ripple marks,the depositional environment is interpreted as a relatively stable low energy lacustrine water setting. Conclusions:The synchronous preservation of diverse organisms suggests that during the Late Jurassic,the lake underwent severe contraction,a dramatic reduction in water extent,a hot and arid climate,and a general deterioration of the ecological conditions.