After detailed studies of leaf area, leaf shape index, petiole length, stomatal density, stomatal index, and carbon isotope discrimination of Ginkgo biloba L., growing in Northwest China, the change trends of these parameters with an altitude gradient and their differences between sun and shade leaves were assessed. The results show that leaf area, petiole length, and stomatal parameters have no obvious linear relationship with altitude, but the carbon isotope discrimination shows a negative correlation with altitude, which has a potential to be an applicable paleo-altimeter. The results also suggest that the differences in stomatal density and stomatal index between sun and shade leaves had more influence on paleoelevation reconstruction than that in other parameters. Based on the linear and nonlinear correlations between carbon isotope discrimination and altitude, the paleoelevation evolution during the Middle Jurassic of the Yaojie Basin, Lanzhou in Gansu Province was estimated. The results show that the paleoelevation of the Yaojie Basin increased at first, and then decreased from the Aalenian to the early Bajocian and then to the late Bajocian in the Middle Jurassic.
Solenites vimineus (Phillips) Harris (Ginkgophyta) specimens with well-preserved cuticles were collected from five different beds in the oil shale member of the Middle Jurassic Yaojie Formation in the Yaojie Basin, Gansu Province, northwestern China. Gross morphology and fine structures of the fossil leaves were studied, and stomatal parameters were analyzed, according to which, the paleoatmospheric CO2 concentration can be deduced as 1512-1896 ppm that would have caused an increase in mean temperature of about 6.5-7.4℃. Carbon isotopes from the fossils indicate that the carbon isotopic discrimination and water use efficiency (WUE) of S. vimineus were raised nearly obtaining the ideal physiologic state in increased CO2 concentrations and temperature conditions, suggesting that S. vimineus records the paleoenvironmental information of the Middle Jurassic Yaojie Basin and can be used for environmental reconstruction.
YAN DeFeiSUN BaiNianXIE SanPingLI XiangChuanWEN WenWen
