Geochemistry of the Shaximiao Formation in a dinosaur fossil site, Guangyuan, Sichuan, and its implications for the source area and paleoweathering

Abstract：The site of the Guangyuan dinosaur fossil is an important fossil site of Middle Jurassic dinosaurs in the Sichuan basin. Dinosaur fossils are buried in argillaceous rocks of the Middle Jurassic Shaximiao Formation. The major element, trace element and REE compositions of argillaceous rocks of the Shaximiao Formation in the dinosaur fossil site in Guangyuan, Sichuan, are studied and the provenance, tectonic setting and weathering of the provenance are discussed according to the geochemical characteristics of the argillaceous rocks. The major and trace elements indicate that felsic rocks predominate in the provenance and that the tectonic setting is the passive continental margin. The chemical index of alteration (CIA) and index of chemical variation (ICV) indicate that their provenance underwent moderate chemical weathering processes, which suggests that the dinosaurs lived in a semiarid climatic environment in the Middle Jurassic.