Glacial history of sub-Antarctic South Georgia based on the submarine geomorphology of its fjords
Glacial history of sub-Antarctic South Georgia based on the submarine geomorphology of its fjords
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DOI：
10.1016/j.quascirev.2013.12.005
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发表时间：
2014-04-01
影响因子：
4
通讯作者：
Evans, David J. A.
中科院分区：
文献类型：
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作者：
Hodgson, Dominic A.;Graham, Alastair G. C.;Evans, David J. A.
我们提出了多波束条带测深调查的主要峡湾周围的亚南极岛屿的南格鲁吉亚，以确定冰川地貌，并确定相对的时间和过去的冰川进退的程度。水深测量数据揭示了一系列冰川特征，包括终端，后退和截断冰碛，深（远）外和浅（近）内盆地和跨陆架槽。这些提供了通过几个冰川循环的冰川前进和后退的证据。在不同的峡湾中观察到一个几乎一致的模式，大规模的海底地貌特征，表明类似的响应边缘的岛屿冰帽过去的气候强迫。基于海底特征与其放射性碳和宇宙成因同位素测年的陆地对应物之间的关系的相对年代学表明，广泛观察到的内盆地冰碛可追溯到最后一次主要冰川推进或末次盛冰期，而深盆地冰碛可能可追溯到更早的时期（前LGM）更广泛的冰川作用，我们推测这对应于MIS 6。在深盆地的两侧，一系列截断的冰碛显示了前冰期的冰前进位置。交叉陆架槽和中槽冰碛被解释为更广泛的冰川作用的产物，早于这里绘制的峡湾地貌，因此可能比MIS6更古老。这一假说表明南格鲁吉亚的冰川历史与巴塔哥尼亚中部（南纬46度）相似，那里的一系列更新世冰川（MIS 20和更年轻）延伸到LGM界限之外，最广泛的冰川前进发生在c。1.1 MA. (C)2014作者由爱思唯尔有限公司出版。保留所有权利。
We present multibeam swath bathymetric surveys of the major fjords surrounding the sub-Antarctic island of South Georgia to characterise the glacial geomorphology and to identify the relative timings and extent of past glacial advance and retreat. Bathymetry data revealed a range of glacial features including terminal, retreat and truncated moraines, deep (distal) outer and shallow (proximal) inner basins and cross shelf troughs. These provide evidence of glacial advance and retreat through several glacial cycles. A near consistent pattern of large scale submarine geomorphological features was observed in the different fjords suggesting a similar response of margins of the island ice cap to past climate forcing. A relative chronology based on the relationships between the submarine features with their radiocarbon and cosmogenic isotope dated terrestrial counterparts suggests that widely observed inner basin moraines date from the last major glacial advance or Last Glacial Maximum, while deep basin moraines may date from an earlier (pre-LGM) more extensive glaciation, which we speculate corresponds to MIS6. On the sides of the deep basins a series of truncated moraines show ice advance positions from preceding glacial periods. The cross shelf troughs, and mid-trough moraines are interpreted as the product of much more extensive glaciations that predate the fjord geomorphology mapped here, thus possibly older than MIS6. This hypothesis would suggest that South Georgia followed a glacial history similar to that of central Patagonia (46 degrees S) where a series of Pleistocene glaciations (of MIS 20 and younger) extended beyond LGM limits, with the most extensive glacial advance occurring at c. 1.1 Ma. (C) 2014 The Authors. Published by Elsevier Ltd. All rights reserved.