10:45 AM - 12:15 PM
[BCG07-P10] Aromatic hydrocarbon signatures reveal evidence of paleo-wildfires during the Lower Cretaceous period in the Kitadani Formation, Tetori Group, Japan
Keywords:Tetori Group, Cretaceous , Albian, Wildfire, Paleoenvironment, PAHs
The thermal maturity of organic matter in the Kitadani Formation was estimated to be equivalent to vitrinite reflectance value of ca. 0.8% (oil window) based on methylphenanthrene maturity indices (MPI-1 & MPR). Diversity in the compositions of PAHs was observed among sedimentary rock samples of the Kitadani Formation, which were collected from different depositional environments such as distinctive fossil-bearing horizons (bonebeds and pterosaur track layer), floodplains, and abandoned channels. However, coronene, a product of high-temperature combustion, was consistently detected in sedimentary rock samples, suggesting recurring occurrence of high-temperature biomass burning around the river during Albian. By combining the PAHs compositions obtained in this study with the data from previous study [2], we found the coronene content in the Kitadani Formation was significantly higher than those in lower stratum of the Tetori Group and Kuzuryu Group, potentially indicating an increase in fire frequency from Aptian to Albian age. The record of paleo-wildfire during the deposition of the Kitadani Formation in the Kitadani Dinosaur Quarry was likely a result of multiple factors, including the increase in atmospheric oxygen concentration [1] and the warming and aridification during the late stage of the Tetori Group’s deposition as suggested by plant fossil assemblages and paleosol analysis [3].
[1] Brown et al. (2021). Cretaceous Research, 36, 162-190.
[2] Hasegawa & Hibino. (2011). Island Arc, 20(1), 23-34.
[3] Sakai et al. (2018). Jour. Geol. Soc. Japan, 124, 171-189.