| 引用本文: | 杨帆,杨国林,高龙,祁桃霞,魏钱伟,邓鹏.2026.甘肃宝积山盆地中侏罗世两种植物化石及其古环境意义[J].地球环境学报,17(3):752-761 |
| YANG Fan,YANG Guolin,GAO Long,QI Taoxia,WEI Qianwei,DENG Peng.2026.Two plant fossils from the Middle Jurassic in Baojishan Basin, Gansu Province and its paleoenvironmental significance[J].Journal of Earth Environment,17(3):752-761 |
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| 摘要: |
| CO2作为一种主要温室气体, 影响着全球气候变化, 了解地质历史时期的CO2浓度变化对于解释当今与预测未来气候发展具有重要意义。植物作为环境变化的指示剂, 其在演化过程中记录了地质历史时期气候变化的重要指示信息。通过宏观和微观特征对比, 将两块采自甘肃宝积山中侏罗世植物化石样品鉴定为狭叶拟刺葵Phoenicopsis (Phoenicopsis) angustifolia Heer和楔拜拉属Sphenobaiera jugata, 并利用气孔比率法定量重建中侏罗世早期的古大气CO2浓度分别为1343.01 μL/L和1353.63 μL/L, 两个数值均处于GEOCARB Ⅲ碳平衡模型的可靠误差范围内, 表明狭叶拟刺葵和楔拜拉是恢复古大气CO2浓度的良好材料。 |
| 关键词: CO2浓度 植物化石 中侏罗世 气孔参数 宝积山盆地 |
| DOI：10.7515/JEE2023115 |
| CSTR：32259.14.JEE2023115 |
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| Two plant fossils from the Middle Jurassic in Baojishan Basin, Gansu Province and its paleoenvironmental significance |
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YANG Fan1，YANG Guolin1，GAO Long1，QI Taoxia1，WEI Qianwei1，DENG Peng2
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1. Bailie School of Petroleum Engineering, Lanzhou City University, Lanzhou 730070 , China ； 2. Gansu Geological Museum, Lanzhou 730030 , China
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| Abstract: |
| Background, aim, and scope Global warming caused by the greenhouse effect has become one of the most concerning environmental problems in recent years. As a major greenhouse gas, CO2 plays an important role in the worldwide climate. Understanding alterations in CO2 concentrations throughout geological history is of great significance for determining the present climate system and predicting future climate development. As indicators of environmental change, plants record important information about climate change during geological periods through their evolution. This study aimed to apply stomatal parameters of fossilized plants to reconstruct paleoatmospheric CO2 concentrations using the stomatal ratio method. It further explored changes in CO2 levels during the Middle Jurassic and their paleoclimatic significance. Materials and methods This study employed two plant fossils collected from the coal-bearing strata of the Middle Jurassic Yaojie Formation (J2y) in the Baojishan Basin (36°40'—36°50'N, 107°47'—105°00'E), Gansu Province, China, as the research material. Their macroscopic morphology was described, and microscopic features were observed. By calculating stomatal parameters and paleoatmospheric CO2 concentrations, the paleoenvironment of the Baojishan Basin was reconstructed. Results This study reports two plant fossils in Middle Jurassic from the Baojishan Basin. By analyzing their macroscopic and microscopic characteristics, the fossils were identified as Phoenicopsis (Phoenicopsis) angustifolia Heer and Sphenobaiera jugata. The stomatal apparatus of Ph. angustifolia was hypostomatic, elongated, and rectangular, measuring approximately 22—48 μm in length and 9—16 μm in width. The stomata were elliptical, the guard cells were kidney-shaped, and the subsidiary cells numbered 4—8. The stomatal density and index were 39—61 per mm2 and 4.86%—6.03%, respectively. The stomatal apparatus of S. jugata was hypostomatic and bore a relatively large number of stomata, arranged in an inconspicuous longitudinal row within the interveinal bands and occasionally on the veins. The stomatal slit was roughly parallel to the veins; the guard cells were sunken, and subsidiary cells numbered 4—6. The stomatal density and index were 23—39 per mm2 and 4.89%—5.68%, respectively. Using two fossil materials, the stomatal ratio method was employed to reconstruct paleoatmospheric CO2 concentrations during the early Middle Jurassic, and they were 1343.01 μL/L and 1353.63 μL/L, respectively. Discussion The two fossil specimens were compared in detail with extant plants and related fossil species belonging to the same genera. One specimen showed 5—8 linear leaves with contracted bases and parallel veins. Based on these morphological characteristics, the fossil was identified as the genus Phoenicopsis. The epidermal cell structure of the fossilized leaves was hypostomatic, suggesting its classification within the subgenus Phoenicopsis. The present specimen closely resembled a narrow-leaved Phoenicopsis type specimen from the Irkutsk Basin of Siberia, which had leaves 4—5 mm wide, with 6—10 veins and lacking fine inter-veins. Therefore, the present specimen was assigned to Ph. angustifolia Heer. The terminal branch system of the second fossil specimen comprised long and short branches; each branch was 6 cm long and about 5 mm wide. Each long branch was 4—5 mm in diameter and had a smooth surface. These branches diverged at an angle of about 50° and bore several short branches arranged in two spiral rows, at a general spacing of 2—3 cm. The present specimen closely related to S. jugata. Previous studies on Middle Jurassic plant fossils from Gansu Province have used the stomatal parameter or stomatal ratio method to reconstruct paleoatmospheric CO2 concentrations for various plant fossils. This present study further explored variations in Middle Jurassic paleoatmospheric CO2 concentrations and their paleoclimatic significance using this method. The CO2 levels of the early Middle Jurassic were 1343.01 μL/L for Phoenicopsis and 1353.63 μL/L for Sphenobaiera, and the two values fall within the reliable error range of the GEOCARB Ⅲ carbon balance model and are consistent with paleoatmospheric CO2 estimates reported from other regions of the same period. Conclusions The average paleoatmospheric CO2 concentrations reconstructed employing the stomatal ratio method were close to the simulation curve of the GEOCARB Ⅲ carbon balance model. The values indicate that Ph. angustifolia and S. jugata are suitable materials for reconstructing the volume fraction of CO2 within the paleoatmosphere. Recommendations and perspectives Further research is needed to verify the accuracy and applicability of the method. Future studies should incorporate wider variety of reconstruction methods and models, covering not only paleoatmospheric CO2 but also other environmental parameters, to provide a more comprehensive understanding of the regional paleoenvironment. |
| Key words: carbon dioxide concentration plant fossil Middle Jurassic stomatal parameters Baojishan Basin |
