Rapid preservation of Jehol Biota in Northeast China from high precision 40Ar/39Ar geochronology
Rapid preservation of Jehol Biota in Northeast China from high precision 40Ar/39Ar geochronology
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DOI：
10.1016/j.epsl.2022.117718
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发表时间：
2022-09
影响因子：
5.3
通讯作者：
Youjuan Li;B. Jicha;Zhi-Feng Yu;Huaichun Wu;Xiaolin Wang;B. Singer;Huaiyu He;Zhonghe Zhou
中科院分区：
文献类型：
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作者：
Youjuan Li;B. Jicha;Zhi-Feng Yu;Huaichun Wu;Xiaolin Wang;B. Singer;Huaiyu He;Zhonghe Zhou
辽宁早白垩世热河生物群记录了该地区动物群的多样性、丰富性和复杂性。义县组下段陆家屯冲积-河流相地层和尖山沟湖相地层分别产出了保存异常完好的三维和有关节的恐龙和哺乳动物化石以及二维原始鸟类/有羽毛恐龙化石。已发表的两个化石层的40 Ar/39 Ar年龄的不确定度为± 0.4 ~ 1.0 Ma（± 2σ分析不确定度），这反映了对大量的、潜在的非均匀的长石晶体群体的测量。更精确的限制生物辐射的时间和持续时间记录的这个序列可以进一步量化的进化模式和重要的早白垩世动物和植物的多样化率。40 Ar/39 Ar单晶熔融实验结果表明，尖山沟和陆家屯化石层的沉积年龄分别为125.374 ± 0.085和125.572 ± 0.120Ma，125.541 ± 0.099和125.793 ± 0.127Ma。这些年龄表明尖山沟化石层下部与陆家屯化石层几乎是同期沉积的。因此，鲁家屯化石层中的恐龙化石和尖山沟化石层中的有羽毛恐龙/原始鸟类化石反映的群体死亡事件几乎是同时代的，而且是短暂的。这些40 Ar/39 Ar年龄与尖山沟化石层中湖相沉积物的天文年代学和古地磁结果相结合，不仅精确了存款中原始鸟类和有羽毛恐龙的持续时间和快速辐射，而且还表明在当前地质时标（GTS 2020）中巴列姆阶内的磁极性时界分布需要修订。
In Liaoning Province, Northeastern China, the Early Cretaceous Jehol Biota records significant evolution and radiation of fauna in terms of diversity, abundance and complexity. The alluvial-to-fluvial Lujiatun and lacustrine Jianshangou beds of the lower Yixian Formation yield exceptionally well-preserved three-dimensional and articulated dinosaur and mammal fossils, and two-dimensional primitive birds/feathered dinosaurs, respectively. Published40Ar/39Ar ages for the two fossil beds have uncertainties of ± 0.4 to 1.0 Ma (± 2σanalytical uncertainty), and these reflect the measurement of large, and potentially heterogeneous, populations of feldspar crystals. More precise constraints on the timing and duration of biological radiation recorded by this sequence can further quantify evolutionary patterns and rates of diversification of important Early Cretaceous animals and plants. Single crystal40Ar/39Ar fusion experiments on sanidine from intercalated ash beds yield dates that constrain the deposition of the Jianshangou and Lujiatun fossil beds to between 125.374 ± 0.085 and 125.572 ± 0.120 Ma, and 125.541 ± 0.099 and 125.793 ± 0.127 Ma, respectively. These ages indicate that the lower part of Jianshangou fossil bed was deposited nearly contemporaneously with the Lujiatun fossil bed. Thus, mass mortality events reflected by dinosaur fossil concentrations in the Lujiatun fossil bed and feathered dinosaur/primitive bird fossils in the Jianshangou fossil bed were nearly coeval and short-lived. These40Ar/39Ar ages, combined with astrochronologic and paleomagnetic results from the lacustrine sediments in the Jianshangou fossil bed, not only refine the duration and rapid radiation of primitive birds and feathered dinosaurs in the deposit, but also suggest that the distribution of magnetic polarity chron boundaries within the Barremian stage in the current geologic time scale (GTS 2020) requires a revision.