Stratigraphy, sedimentology and palaeoenvironment of the dinosaur-bearing Late Cretaceous Zhengyang Formation in the Zhengyang Basin, Chongqing, South China

Abstract Situated within the southwestern segment of Chongqing, the Zhengyang Basin formed one of the intermountain basins among the Yanshanian orogenic belt that developed during the Late Cretaceous. The Zhengyang Basin preserves a > 100 m-thick Late Cretaceous terrestrial successions, named as the Zhengyang Formation characterized by debris-flow deposits and fluvial-lacustrine units. Recently, abundant dinosaur fossils have been collected from this formation, including hadrosaurs, titanosaurs and theropods, providing the first substantial evidence of a Late Cretaceous dinosaur fauna in South China. We herein report detailed stratigraphic architecture, dinosaur fossil assemblage, sedimentary and palaeoenvironmental features of the Zhengyang Formation in the Zhengyang Basin. The information suggests that the dinosaurs lived in a restricted intermountain basin, of which the palaeo-climate was significantly influenced by a transition from overall humid to arid sedimentary condition. Our data lead to new evaluation of early Late Cretaceous dinosaur evolution, and provide new clues for investigation on the contemporary terrestrial palaeoenvironmental and palaeoclimatic features in the mid-low latitude area of East Asia. The stratigraphic features of the Zhengyang Formation also provide new insights into showing lateral correlation of the Late Cretaceous terrestrial successions in East Asia.