Geological insights from the newly discovered granite of Sif Island between Thwaites and Pine Island glaciers
Geological insights from the newly discovered granite of Sif Island between Thwaites and Pine Island glaciers
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思韦茨冰川和松岛冰川之间新发现的锡夫岛花岗岩的地质见解
DOI：
10.1017/s0954102023000287
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发表时间：
2024
影响因子：
1.6
通讯作者：
Hammond, Samantha J.
中科院分区：
文献类型：
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作者：
Marschalek, James W.;Thomson, Stuart N.;Hillenbrand, Claus-Dieter;Vermeesch, Pieter;Siddoway, Christine;Carter, Andrew;Nichols, Keir;Rood, Dylan H.;Venturelli, Ryan A.;Hammond, Samantha J.
大规模的地质结构控制了海床的长期发展，从而控制了西南极冰盖的流动。然而，完整的冰层覆盖掩盖了斯威茨冰川和松岛冰川下断层和地质边界的年龄和确切位置，这两个冰川是阿蒙森海地区的两个主要WAIS出口。在这里，我们描述了这两个冰川之间唯一的岩石露头，它是在21世纪10年代初缓慢流动的沿海冰撤退时暴露出来的，形成了新的Sif岛。该岛礁由花岗岩组成，锆石U-Pb年龄为177-174 Ma，初始Nd、87 Sr/86 Sr和Hf同位素组成分别为-2.3，0.7061和-1.3。这些特征类似于瑟斯顿岛/南极半岛地壳块体岩石，强烈表明锡夫岛花岗岩属于该省，并将地壳块体与思韦茨冰川或其东部剪切边缘下的玛丽伯德地省的边界。低温热年代学数据显示，花岗岩在侵位后经历了快速冷却，在~100-90 Ma时再次快速冷却，然后保持在地球表面附近直到现在。这些数据有助于确定松岛冰川下主要构造结构到晚白垩世的垂直位移。
Large-scale geological structures have controlled the long-term development of the bed and thus the flow of the West Antarctic Ice Sheet (WAIS). However, complete ice cover has obscured the age and exact positions of faults and geological boundaries beneath Thwaites Glacier and Pine Island Glacier, two major WAIS outlets in the Amundsen Sea sector. Here, we characterize the only rock outcrop between these two glaciers, which was exposed by the retreat of slow-flowing coastal ice in the early 2010s to form the new Sif Island. The island comprises granite, zircon U-Pb dated to ~177–174 Ma and characterized by initial ɛNd, 87Sr/86Sr and ɛHf isotope compositions of -2.3, 0.7061 and -1.3, respectively. These characteristics resemble Thurston Island/Antarctic Peninsula crustal block rocks, strongly suggesting that the Sif Island granite belongs to this province and placing the crustal block's boundary with the Marie Byrd Land province under Thwaites Glacier or its eastern shear margin. Low-temperature thermochronological data reveal that the granite underwent rapid cooling following emplacement, rapidly cooled again at ~100–90 Ma and then remained close to the Earth's surface until present. These data help date vertical displacement across the major tectonic structure beneath Pine Island Glacier to the Late Cretaceous.