Features of molecular fossils at the Shibei dinosaur fossil site—Early Jurassic red beds—in Gongxian, Sichuan, and their paleoenvironmental significance

Abstract：A series of molecular fossils, including n-alkanes, pristine, phytane, extended tricyclic terpanes, hopanes and regular steranes, have been identified from the Shibei dinosaur fossil site－Early Jurassic red beds－in Gongxian, Sichuan, through GC/MS analysis. These fossils are supposed to be derived from lower thallophytes and aquatic and terrestrial higher plants. The features of these molecular fossils are used to study the paleoenvironment during the dinosaur age. The Pr/Ph suggests that the sedimentary environment at the burial site of the dinofossils should be a limnetic, non-reductive lake. High-molecular-weight (>C21) n-alkanes in the studied samples are dominated by C25 n-alkanes related to aquatic macrophytes,, and in addition, C27－C31 n-alkanes derived from terrestrial higher plants are also present. This suggests that aquatic higher macrophytes flourished in the lake of the study area in the Early Jurassic, while woody plants and herbaceous plants grew in the watershed around the water body. This study shows that molecular fossils have a potential in reconstructing the paleoenvironment.