甘肃北山早白垩世似银杏化石的发现:兼论甘肃侏罗-白垩纪古大气CO_(2)变化  

Discovery of Early Cretaceous Ginkgoites in Beishan, Gansu Province: Also on Changes of Paleoatmospheric CO_(2) in Jurassic to Cretaceous in Gansu Province

作　　者：任文秀 韩磊[1] 吴光涛 唐德亮 孙柏年 吴靖宇 Ren Wenxiu;Han Lei;Wu Guangtao;Tang Deliang;Sun Bainian;Wu Jingyu(School of Earth Sciences,Lanzhou University,Lanzhou 730000,China;Geological Survey of Gansu Province,Lanzhou 730000,China;State Key Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Paleontology and Center for Excellence in Life and Paleoenvironment,Chinese Academy of Sciences,Nanjing 210008,China)

机构地区：[1]兰州大学地质科学与矿产资源学院,甘肃兰州730000 [2]甘肃省地质调查院,甘肃兰州730000 [3]现代古生物学和地层学国家重点实验室(中国科学院南京地质古生物研究所),江苏南京210008

出　　处：《地球科学》2024年第1期209-223,共15页Earth Science

基　　金：第二次青藏高原综合科学考察项目(No.2019QZKK0704);甘肃省自然科学基金项目(No.20JR5RA039);国家自然科学基金项目(Nos.42362003,41972010,32170222,31870200);现代古生物学和地层学国家重点实验室(中国科学院南京地质古生物研究所)项目(Nos.213115,183124)。

摘　　要：银杏类化石的微细构造是定量估算古大气二氧化碳浓度的良好材料.首次报道了甘肃北山中口子盆地早白垩世赤金堡组似银杏属化石,通过宏观和微观特征对比将其鉴定为Ginkgoites sibirica.利用气孔比率法定量重建Hauterivian-Barremian期的古大气CO_(2)浓度为766~1 277 ppmv.结合前人数据,利用光合气体交换模型定量重建了甘肃省早侏罗世-早白垩世古大气CO_(2)浓度及变化趋势,侏罗纪普林斯巴期(Pliensbachian)、阿林期(Aalenian)、巴柔期早期(Early Bajocian)、巴柔期晚期(Late Bajocian)的古大气CO_(2)浓度分别为1 136 ppmv、927 ppmv、643 ppmv和785 ppmv;早白垩世Hauterivian-Barremian期的CO_(2)浓度为548 ppmv.结果显示早、中侏罗世二氧化碳浓度较高,向白垩纪呈下降趋势,早白垩世早中期达到低点后呈现缓慢波动上升;早白垩世晚期达到顶点,然后缓慢下降.研究表明光合气体交换模型可作为恢复古气候变化的有效手段.Epidermal features of fossil ginkgophyta are one of the good materials for estimating the paleoatmospheric CO_(2) concentration.In this study,a fossil Ginkgoites species,Ginkgoites sibirica is firstly described based on leaf morphology and epidermal features from the Lower Cretaceous Chijinbao Formation in the Zhongkouzi Basin,Beishan area,Northwest China.The paleo-CO_(2) was 766-1277 ppmv during the Hauterivian to Barremian based on the stomatal ratio method,which is consistent with the results of other studies.The CO_(2) variation trend during the Early Jurassic to the Early Cretaceous is reconstructed based on the leaf gas-exchange model in combination with previous data.The paleo-CO_(2) was 643-1136 ppmv during the Jurassic and 548 ppmv during the Hauterivian to Barremian.The results show that the CO_(2) concentration was high in the Early and Middle Jurassic,with a decreasing trend toward the Cretaceous,and then showed a significant increase during Early and Middle Cretaceous.The paleo-CO_(2) reached its peak during the late Early Cretaceous,and then decreased significantly afterwards.Studies have shown that the leaf gas-exchange model can be an effective proxy for reconstructing paleoclimate.

关 键 词：似银杏属 古大气CO_(2) 光合气体交换模型 定量重建 中生代 古气候 

分 类 号：P52[天文地球—古生物学与地层学]