Mesozoic rocks across East Asia contain spectacular plant and animal fossils that are key to understanding the evolution of early mammals, primitive birds, and several groups of feathered dinosaurs. A multi-chronometer (40Ar/39Ar and U-Pb) approach to dating abundant volcanic tuffs and volcaniclastic sedimentary rocks from these classic and newly discovered fossil localities will provide a robust geochronological calibration for some of the earliest mammals, birds and feathered dinosaurs.
The recent addition of Su-chin Chang, who did her Ph.D. thesis research on high-precision 40Ar/39Ar dating with Paul Renne at the Berkeley Geochronology Center, has expanded our commitment to both the inter-lab and interdisciplinary elements of the EARTHTIME mission. Chang’s research focuses on providing high precision age constraints for Mesozoic biological evolution in Asia. The Cretaceous Jehol Biota, defined as the characteristic Eosestheria-Ephemeropsis-Lycoptera assemblage, is widely distributed in eastern and central Asia (Grabau, 1928; Gu, 1962; Chen, 1988; Chen and Jin, 1999). Since the 1990s, abundant and varied fossils, including plants, insects, frogs and salamanders, dinosaurs, pterosaurs, choristoderes, birds, mammals and freshwater invertebrates, have been discovered from the Dabeigou Formation, the Yixian Formation and the Jiufotang Formation in Liaoning Province, Hebei Province and Inner Mongolia, NE China (Chen and Jin, 1999; Zhou et al., 2003; Zhang et al., 2003; Zhou, 2004; Zhang et al., 2008). Well-preserved Jurassic terrestrial fossils (including plants, insects, salamanders, pterosaurs, and mammals) were discovered in the Haifanggou Formation and the overlying Lanqi Formation (or their correlative strata) in NE China. The less-studied Haifanggou-Lanqi Fossils (HLF) and the well-known Jehol Biota are known in the same geographic area, but the fossils were discovered from distinct geologic formations now believed to be of different ages (Yang and Li, 2008). The lateral extension of the HLF and its correlation with the Daohugou Biota of Inner Mongolia is unclear. However, HLF have greatly increased our knowledge of Mesozoic terrestrial ecosystems.
S. Chang, H. Zhang, P.R. Renne, and Y. Fang, 2009. High-precision 40Ar/39Ar age for the Jehol Biota. Palaeogeography, Palaeoclimatology, Palaeoecology 280, 94-104.
S. Chang, H. Zhang, P.R. Renne, and Y. Fang, 2009. High-precision 40Ar/39Ar age constraints on the basal Lanqi Formation and its implications for the origin of angiosperm plants. Earth and Planetary Science Letters279, 212-221.
S. Chang, H. Zhang, S. Hemming, Y. Fang and G. Mesko, High-precision 40Ar/39Ar ages for the Jehol fossil-bearing formations in SE China. AGU Fall Meeting (2009).
S. Chang, H. Zhang, S. Hemming, P. Renne and Y. Fang, High-precision 40Ar/39Ar geochronological constraints on the evolution of Mesozoic ecosystems in East Asia: Rates and Dates. GSA Annual Meeting (2009).
S. Chang, H. Zhang, P. R. Renne and Y. Fang, High-precision 40Ar/39Ar age for the Jehol Biota. AGU Fall Meeting (2008).
S. Chang, H. Zhang, P. R. Renne and Y. Fang, High-precision 40Ar/39Ar age constraints on the basal Lanqi Formation and its implications for floral evolution and paleoenvironment. GSA Annual Meeting (2008).