Asymmetric ice-sheet retreat pattern around northern Scotland revealed by marine geophysical surveys
Asymmetric ice-sheet retreat pattern around northern Scotland revealed by marine geophysical surveys
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DOI：
10.1017/s1755691015000109
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发表时间：
2014-12
影响因子：
1.2
通讯作者：
T. Bradwell;M. Stoker
中科院分区：
文献类型：
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作者：
T. Bradwell;M. Stoker
摘要本研究利用海洋地球物理数据，主要是单波束和高分辨率多波束回声测深仪测深，结合地震海底剖面和现有的第四纪地质信息，绘制了苏格兰北方大陆架周围从刘易斯以西到奥克尼群岛以北的大面积海底（150，000平方公里）的冰川地貌图。我们的新地图揭示了海底冰川地貌的详细模式，主要是冰碛，与覆盖苏格兰和大部分大陆架的冰盖有关，这些冰盖是在晚Weichselian冰期和早在中更新世至晚更新世期间。重建撤退模式的基础上的地貌证据突出了大量不同的撤退阶段和不对称，不均匀的演变，这冰盖部门在晚Weichselian冰消期。时间等效的冰锋重建表明，海洋部门的冰盖，如明奇，改变了他们的几何形状显着，也许很快，而其他部门保持相对不变和稳定。我们认为，这种行为，主要由床地形/测深和冰动力学，导致重组的后期Weichselian冰盖，因为它撤退到两个主要的冰中心：一个在苏格兰西部和其他奥克尼群岛和设得兰群岛。这种退缩模式表明西北刘易斯冰川消退相对较早（约。25 ka BP）和苏格兰西北部的山脉-后者可能形成了一个巨大的无冰陆地走廊。我们的重建与大多数之前的合成不同，但得到了独立绘制的海上第四纪序列和关键陆上测年限制的强烈支持。
ABSTRACT This study uses marine geophysical data, principally single-beam and high-resolution multibeam echo sounder bathymetry, combined with seismic sub-bottom profiles, and existing Quaternary geological information, to map the glacial geomorphology of a large area of seafloor (∼50,000 km2) on the continental shelf around northern Scotland, from west of Lewis to north of the Orkney Islands. Our new mapping reveals the detailed pattern of submarine glacial landforms, predominantly moraines, relating to ice sheets that covered Scotland and much of the continental shelf during the Late Weichselian glaciation and earlier in the Mid to Late Pleistocene. The reconstructed retreat pattern based on geomorphological evidence highlights the large number of different retreat stages and the asymmetric, non-uniform evolution of this ice sheet sector during Late Weichselian deglaciation. Time-equivalent ice-front reconstructions show that marine sectors of the ice sheet, such as the Minch, changed their geometry significantly, perhaps rapidly; whilst other sectors remained relatively unchanged and stable. We suggest that this behaviour, governed principally by bed topography/bathymetry and ice dynamics, led to reorganisation of the Late Weichselian ice sheet as it retreated back to two main ice centres: one in Western Scotland and the other over Orkney and Shetland. This retreat pattern suggests relatively early deglaciation of NW Lewis (ca. 25 ka BP) and the mountains of far NW Scotland – the latter possibly forming a substantial ice-free land corridor. Our reconstructions differ from most previous syntheses, but are strongly supported by the independently-mapped offshore Quaternary succession and key onshore dating constraints.