以角质层保存完好的4种银杏类化石为研究对象,通过对叶片角质层气孔参数的详细统计分析,利用气孔指数法和气孔比率法,定量重建了该区中侏罗世阿林期-巴柔期古大气(φ)(CO2).结果显示:通过气孔指数法获得的狭叶拟刺葵、西伯利亚似银杏、敏斯特里拜拉(相似种)、东北拜拉大气(φ)(CO2)均落在GEOCARBⅢ可信误差范围之外,而气孔比率法获得的狭叶拟刺葵、西伯利亚似银杏、敏斯特里拜拉(相似种)、东北拜拉大气(φ)(CO2)均落在GEOCARBⅢ可信误差范围之内.说明对于恢复侏罗纪的大气(φ)(CO2)气孔比率法更加可靠.由气孔比率法所得的古大气(φ)(CO2)中,西伯利亚似银杏所得结果最接近最佳拟合线,其次是狭叶拟刺葵,拜拉属植物所得结果较低.表明似银杏属植物化石获得的古大气(φ)(CO2)更加准确.最后确定出内蒙古准格尔旗西南部中侏罗世阿林期-巴柔期的(φ)(CO2)为1.413×10-3.%Using the method of stomatal index and stomatal radio,the stomatal parameters on the epidermis were studied,based on the materials of four species of ginkgo fossils from the study area,and the paleo-(φ)(CO2)concentrations from Aalenian to Bajocian in the middle Jurassic were reconstructed for Phoenicopsis angustifolia,Ginkgoites sibirica,Baiera cf.miiensteriana and Baiera manchurica respectively by the stomatal index method,which was out of the error range of (φ)(CO2) confidence from GEOCARB Ⅲ.However,the values of paleo-(φ)(CO2) were obtained by using the method of stomatal ratio,which was plotted within the error range of (φ)(CO2) confidence.The two results indicated that the stomatal ratio method is more reliable than the stomatal index method in reconstructing Jurassic (φ)(CO2) concentration.For the paleo-(φ)(CO2)values obtained from the stomatal ratio method,Ginkgoites sibirica was more adjacent to the optimum line of GEOCARB]Ⅲ.The second was Phoenicopsis angustifolia.The results of Baiera were lower,which were reconstructed respectively by Baiera manchurica and Baiera cf miiensteriana,suggesting that the paleo-(φ)(CO2)concentration reconstructed from ginkgoales fossils was more precise.As a result,the paleo-(φ)(CO2) concentration of the southwestern margin of Junger Banner,Inner Mongolia from Aalenian to Bajocian in the middle Jurassic is ascertained to be 1.413 × 10-3.
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