Middle Jurassic Ginkgo leaves from the Daohugou area, Inner Mongolia, China and their implication for palaeo-CO2 reconstruction

Well-preserved Ginkgo leaves with cuticle were collected from the Middle Jurassic Jiulongshan Formation in the Daohugou area, Inner Mongolia, China, which form the common elements in the Daohugou flora. Three new species of Ginkgo are recognized and their leaf morphology and cuticular structure are described for the first time. Two different pCO2 proxy models were applied to reconstruct palaeo-atmospheric CO2 concentration by using these new Ginkgo material. NLE (nearest living equivalent) suggests a semi-quantitative pCO2 estimate as 839±99ppmv with Carboniferous standardization and 419±49ppmv with Recent standardization. While Barclay’s revised SI-pCO2 regression suggests the estimates as 405±71ppmv. The results show that the pCO2 estimate is higher than today’s atmospheric CO2 concentration but lower than most of the other results on the Jurassic Period. Combined with the floristic composition, the climate at 165Ma in the Daohugou area is inferred to be warm temperate.