| 摘要: |
| 华南南华系对应于国际上的成冰系，关于其沉积时限长期存在争议。近十余年来，通过高精度锆石U-Pb定年，已经基本敲定南华系的重要时间节点。长安组底界年龄被限定在ca. 717 Ma，莲沱组顶部沉积时间被限定在ca. 714 Ma。长安冰期中期暂时冰退的时间被限定在ca. 690 Ma，冰期终止时间限定在ca. 659 Ma。小行星撞击地球可能导致了长安冰期中期的暂时冰退，这期间形成的风暴沉积构造和丘状交错层理可以提供最直接的沉积学证据。结合世界其它地区报道的年龄，斯图特（长安）冰期的起止时间限定在了717~659 Ma。马力诺（南沱）冰期的启动时间被大致限定为649 Ma，终止时间被限定在ca. 635 Ma。结合世界其它地区年龄数据，马力诺冰期的启动时间可限定在649~639 Ma。随着后续工作的深入，马力诺冰期的启动时间范围应会被进一步缩小。华南南华系沉积时限的准确厘定对于理解全球成冰纪地质－生物－环境事件具有重要意义。马力诺冰期持续时间约14 Myr，远远小于长安冰期的持续时间（约58 Myr）。冰期末期大规模岩浆作用是导致这两次冰期持续时间不同的直接原因。通过模拟计算发现，扬子北缘裂谷岩浆作用可以促使马力诺冰期提前2~5 Myr结束。 |
| 关键词: 南华系 成冰系 沉积时代 长安组 南沱组 |
| DOI：10.19826/j.cnki.1009-3850.2023.01001 |
| 附件 |
| 投稿时间：2022-12-27修订日期：2023-01-04 |
| 基金项目:国家自然科学基金面上项目（42273025），中国科学院地质与地球物理研究所岩石圈演化国家重点实验室开放课题（SKL-Z202001），中国科学院南京地质古生物研究所现代古生物学与地层学国家重点实验室开放课题（223115），中国地质大学（武汉）地质过程与矿产资源国家重点实验室开放课题（GPMR201902） |
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| Research progress on the chronostratigraphic study of Nanhua System in South China. |
| LAN Zhongwu |
(1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beitucheng Xilu, Chaoyang District, Beijing 100029, China;
2. State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 2100083, China;
3. State Key Laboratory of Geological Processes and Mineral Resources, University of Geosciences, Wuhan 430074, China) |
| Abstract: |
| The Nanhuan system in South China correlates with the Cryogenian, depositional age of which remains disputed. In the past decade, key depositional age points of the Nanhuan system have been ascertained by means of high precision zircon U-Pb geochronology. The basal Chang'an Formation is constrained to be ca. 717 Ma, whereas the top Liantuo Formation is constrained to be ca. 714 Ma. Glacial retreat during the middle Chang'an glacial period is constrained to be ca. 690 Ma, and the final glacial retreat for the Chang'an glacial period is constrained to be ca. 659 Ma. In combination with radiometric ages reported from other worldwide regions, the initiation and termination age of the Sturtian glaciation is constrained to be ca. 717-659 Ma. The onset and termination ages of Nantuo glaciation are roughly constrained to be ca. 649 Ma and ca. 635 Ma, respectively. In combination with radiometric ages reported from other worldwide areas, the onset age of the Marinoan glaciation can be constrained to be ca. 649-639 Ma. With ongoing work in future, age span for the initiation of Marinoan glaciation can be further shortened. Precisely dating the depositional age of the Nanhua System in South China will aid us in understanding the global geological and biological events during the glaciation. The duration of Marinoan glaciation is constrained to be ca. 14 Myr, which is much shorter than that of the Sturtian glaciation (ca. 58 Myr). Large-scale magmatism in the end of glaciation is the main reason that induced the difference in the time span of these two glaciations. By means of calculation and climate modelling, we found that magmatism in the northern Yangtze Block can foreshorten the Marinoan glaciation to 2-5 Myr. |
| Key words: Nanhua system Cryogenian depositional age Chang’an Formation Nantuo Formation |
