挪威科技大学 L.C. Haaland课题组的最新研究揭示，U-Pb方解石年龄确定了北极—北大西洋门户的斜向断裂。2024年5月21日出版的《地质学》发表了这项成果。

据介绍，中新世斯瓦尔巴群岛从格陵兰岛分离出来，形成了一个深海门户，使北极和大西洋之间的环流得以实现，极大地改变了全球气候。然而，事件发生的时间仍不清楚。

研究人员在斯瓦尔巴群岛西部海岸发现了限制这一时间的绝佳机会，即，那里的Sarsbukta断层形成了始新世-渐新世Forlandsundet盆地的东部边缘。该研究对断层相关脉体中沉淀方解石进行U-Pb定年，以约束Sarsbukta断层变形和盆地演化的时间。结果显示，最古老的方解石年龄是二叠纪—三叠纪，表明断层沿线的变形长期存在。

介于41-33Ma的一组年龄与Forlandsundet盆地部分地区的化石沉积年龄重叠。这些数据表明，陆上转换张力在一定程度上早于已建立的Chron13(磁极性时间尺度；35.5-33.7Ma)北大西洋扩张脊的重组。最年轻的方解石年龄为13Ma，表明断裂作用在保存完好的盆地填充物沉积后很久还在持续。如果海底扩张标志着大陆地壳扩张的结束，那么Chron5(19.6-9.8Ma)期间的Molloy脊扩张可能是在13Ma之后开始的。

附：英文原文

Title: U-Pb calcite ages date oblique rifting of the Arctic-North Atlantic gateway

Author: L.C. Haaland, T. Slagstad, P.T. Osmundsen, T. Redfield

Issue&Volume: 2024-05-21

Abstract: Miocene breakup of Svalbard from Greenland formed a deep oceanic gateway that enabled circulation between the Arctic and Atlantic Oceans, significantly changing the global climate. However, the timing of events remains unclear. An excellent opportunity to constrain this timing is found onshore western Svalbard, where the Sarsbukta fault forms the eastern margin of the Eocene-Oligocene Forlandsundet basin. Here, we present new results from U-Pb dating of calcite precipitated in fault-related veins to constrain the timing of Sarsbukta fault deformation and the evolution of the basin. Our oldest calcite age is Permo-Triassic, suggesting long-lived deformation along the fault. A cluster of ages between 41 and 33 Ma overlaps with fossil-based depositional ages from parts of the Forlandsundet basin. These data indicate that onshore transtension partly pre-dated the well-established Chron 13 (magnetic polarity time scale; 35.5-33.7 Ma) reorganization of spreading ridges in the North Atlantic. Our youngest age of 13 Ma indicates that faulting persisted long after the preserved basin fill was deposited. If seafloor spreading marked the end of extension of continental crust, Molloy Ridge spreading during Chron 5 (19.6-9.8 Ma) may have initiated after 13 Ma.

DOI: 10.1130/G52140.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G52140.1/644242/U-Pb-calcite-ages-date-oblique-rifting-of-the