甘肃省北山地区早白垩世爬行动物碳氧同位素对古气候的指示
发布时间：2018-11-05 20:48
【摘要】：早白垩世晚期的东亚大陆具有十分独特的拼贴式地理特点,同时遍布丰富的脊椎动物群,是恐龙种群起源和发展的摇篮。纬度温度梯度的变化、天然地理屏障的存在、以及不同的当地环境条件,均可导致生物群的非均匀分布。因此,研究生物的种类及分布特点,可部分恢复其生存环境,为古气候、古地理的重建提供新的视角和有力证据。爬行动物(恐龙、鳄鱼及龟类)磷灰石的稳定同位素已被用来分析及解释古生态及古环境。本文的研究区是甘肃省酒泉市北部的北山地区(马鬃山地区),处于天山兴蒙构造带的西南部,构造变形强烈且复杂,早白垩世时期处于伸展背景下,化石埋藏地以红色陆相碎屑岩为主,为河湖相沉积。采集自研究区下白垩统新民堡群的恐龙、鳄鱼的牙齿及龟甲等化石样品,由于其釉质层及甲壳部分坚硬、致密,抗风化性强和受成岩作用影响小,可利用样品生物磷灰石的磷酸盐氧同位素与大气水的氧同位素分馏关系,及大气水氧同位素与气温的线性方程式,计算得出研究区全年平均气温(MAAT)为19±3℃,同时证明了磷酸盐能够很好地保存原始氧同位素信号不受后期改造;另一方面,利用标本中碳酸盐的碳同位素与植物叶片的碳同位素分馏关系,计算出当地植物类型为C3植物,再根据植物的碳同位素与降水的最小二乘回归方程式,计算得出研究区全年平均降水(MAP)为500±200mm/yr。在气候分带三角图中投图,得到研究区早白垩世的气候类型属于半干旱-干燥森林、草原气候,与前人孢粉学、沉积学研究结果一致。陆生爬行动物氧同位素值高于半水生-水生动物,后者所处水环境的温度波动也比前者要小。植食性恐龙(禽龙、角龙类)有截然不同的碳同位素组成,表明它们的食物来源有区别,可以避免种间竞争从而相互共存。鳄鱼属于冷血动物,生存条件有严格的限定,研究区古纬度(35°N)的温度恰好属于鳄鱼生存温度的临界点。而龟类生存条件较鳄鱼宽泛,再向北仍有存活迹象。
[Abstract]:The East Asian continent in the late early Cretaceous had unique collage geographical characteristics and abundant vertebrate groups, which was the cradle of the origin and development of dinosaur population. The variation of temperature gradient of latitude, the existence of natural geographical barrier and the different local environmental conditions can lead to the inhomogeneous distribution of biota. Therefore, the study of species and distribution characteristics of organisms can partly restore their living environment and provide a new perspective and strong evidence for the reconstruction of paleoclimate and paleogeography. Stable isotopes of apatite from reptiles (dinosaurs, crocodiles and tortoises) have been used to analyze and explain paleoecology and paleoenvironment. The study area of this paper is the Beishan area in the north of Jiuquan City, Gansu Province (Madonshan area), which is located in the southwest of the Xingmeng structural belt of Tianshan Mountain. The tectonic deformation is strong and complex, and the early Cretaceous period is in the extensional setting. The fossils are mainly red continental clastic rocks, which are fluvial and lacustrine deposits. Samples of dinosaurs, crocodiles teeth and tortoise shells from the Lower Cretaceous Xinmin Fort Group in the study area were collected. Due to the hard and dense enamel layers and crustaceans, strong weathering resistance and little diagenesis, The relationship between phosphate oxygen isotope and oxygen isotope fractionation of atmospheric water, and the linear equation of oxygen isotope and temperature of atmospheric water can be used to calculate the annual average air temperature (MAAT) of the study area is 19 卤3 鈩，
本文编号：2313413
[Abstract]:The East Asian continent in the late early Cretaceous had unique collage geographical characteristics and abundant vertebrate groups, which was the cradle of the origin and development of dinosaur population. The variation of temperature gradient of latitude, the existence of natural geographical barrier and the different local environmental conditions can lead to the inhomogeneous distribution of biota. Therefore, the study of species and distribution characteristics of organisms can partly restore their living environment and provide a new perspective and strong evidence for the reconstruction of paleoclimate and paleogeography. Stable isotopes of apatite from reptiles (dinosaurs, crocodiles and tortoises) have been used to analyze and explain paleoecology and paleoenvironment. The study area of this paper is the Beishan area in the north of Jiuquan City, Gansu Province (Madonshan area), which is located in the southwest of the Xingmeng structural belt of Tianshan Mountain. The tectonic deformation is strong and complex, and the early Cretaceous period is in the extensional setting. The fossils are mainly red continental clastic rocks, which are fluvial and lacustrine deposits. Samples of dinosaurs, crocodiles teeth and tortoise shells from the Lower Cretaceous Xinmin Fort Group in the study area were collected. Due to the hard and dense enamel layers and crustaceans, strong weathering resistance and little diagenesis, The relationship between phosphate oxygen isotope and oxygen isotope fractionation of atmospheric water, and the linear equation of oxygen isotope and temperature of atmospheric water can be used to calculate the annual average air temperature (MAAT) of the study area is 19 卤3 鈩，
本文编号：2313413
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