成都理工大学Liang Qi团队在研究四川盆地侏罗纪恐龙骨骼的原位U-Pb测年中取得新进展。相关论文发表在2024年1月16日出版的《地质学》杂志上。

研究人员提出了一种通过激光烧蚀—电感耦合等离子体—质谱测定脊椎动物化石年代的新方法。该方法对华南四川盆地侏罗纪蜥脚类恐龙动物骨腔内沉淀的早期成岩方解石胶结物进行了U-Pb定年。早期成岩方解石的U-Pb年龄为165.3±3.6/5.6 Ma，与周围岩石碎屑锆石年龄的最大沉积年龄165.8±1.0 Ma一致，表明成岩作用发生在蜥脚类恐龙死亡后不久。

这个新年龄表明，华南地区最著名的侏罗纪大型蜥脚类动物群比北美和非洲的恐龙群要古老得多，表明华南地区在地理上是孤立的。来自同一蜥脚类动物的纤维板层骨的自生磷灰石U-Pb测年结果显示更年轻的年龄结果，表明其U-Pb系统行为更为复杂，可能与残留有机质对U的吸收和早期成岩作用后磷灰石的重结晶有关。研究结果表明，骨腔内方解石胶结物的U-Pb定年具有限制脊椎动物化石的埋藏年龄的巨大潜力，这有助于为脊椎动物的辐射和进化构建一个更合理的时间框架。

据了解，脊椎动物化石的直接测年是困难的，因为埋藏后的成岩过程很复杂，而且化石骨材料中放射性同位素(如铀)的浓度通常很低且不均匀。

附：英文原文

Title: In situ U-Pb dating of Jurassic dinosaur bones from Sichuan Basin, South China

Author: Liang Qi, Mingcai Hou, Jacob A. Mulder, Peter A. Cawood, Yao Guo, Shitou Wu, Liangxuan Jiao, Xiaolin Zhang, Hui Ouyang

Issue&Volume: 2024-01-16

Abstract: Direct dating of vertebrate fossils is difficult due to complex postburial diagenetic processes and the often low and heterogeneous concentration of radioisotopes (e.g., U) in fossilized bone material. Here, we demonstrate a novel approach to dating vertebrate fossils via laser ablationinductively coupled plasmamass spectrometry U-Pb dating of early diagenetic calcite cements precipitated within bone cavities of a Jurassic sauropod from the Sichuan Basin, South China. Early diagenetic calcite yielded a U-Pb age of 165.3 ± 3.6/5.6 Ma, in agreement with a maximum depositional age of 165.8 ± 1.0 Ma from detrital zircon ages of the surrounding rocks, suggesting that diagenesis occurred shortly after the death of the sauropod. This new age demonstrates that the best-known Jurassic large sauropod faunas in South China are much older than those in North America and Africa, suggesting the geographical isolation of South China. Authigenic apatite U-Pb dating on the fibrolamellar bones from the same sauropod gave a distinctly younger age, indicating more complex U-Pb system behavior, possibly due to U uptake by residual organic matter and recrystallization of apatite after early diagenesis. Our findings demonstrate that U-Pb dating of calcite cements within bone cavities has significant potential for constraining the burial age of vertebrate fossils, which could aid in constructing a more robust temporal framework for the radiation and evolution of vertebrates.

DOI: 10.1130/G51872.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51872.1/633158/In-situ-U-Pb-dating-of-Jurassic-dinosaur-bonesredirectedFrom=fulltext