Dynamics of the Late Weichselian ice sheet on Svalbard inferred from high‐resolution sea‐floor morphology
Dynamics of the Late Weichselian ice sheet on Svalbard inferred from high‐resolution sea‐floor morphology
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DOI：
10.1111/j.1502-3885.2007.tb01251.x
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发表时间：
2007-08
期刊：
影响因子：
2.2
通讯作者：
D. Ottesen;J. Dowdeswell;J. Landvik;J. Mienert
中科院分区：
文献类型：
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作者：
D. Ottesen;J. Dowdeswell;J. Landvik;J. Mienert
对斯瓦尔巴群岛周围的峡湾和大陆架进行的高分辨率水深测绘显示，由于冰流状况的不同，形成了大中型海底地貌的广泛格局。边缘大型峡湾、陆架和跨陆架海槽地貌上叠加了超大规模冰川线理、侧冰隆、横脊和冰川构造特征。从这些地貌中，我们已经推断出斯瓦尔巴群岛上最后一块冰盖的流动和动力学。主要峡湾及其邻近的跨陆架槽已被确定为冰流排干冰盖的主要路线。在斯瓦尔巴特群岛的西海岸，贝尔松德、伊斯夫约登和孔夫约登都有主要的道路。沿斯瓦尔巴群岛北部边缘，大部分冰流经伍德夫约登跨陆架海槽和维杰德约登-欣洛海峡。跨陆架海槽中具有平行于海槽的冰川线条的大片地区表明，古冰流的冰流速度很快。沿着一些跨陆架海槽的边缘绘制了长达数十公里的横向冰河冰雹图，确定了快速冰流与中间河岸停滞或缓慢流动的冰之间的边界地带。从对斯瓦尔巴群岛周围冰川衍生的海底地貌的解释中，可以得出几个一般性的含义。首先，魏氏晚期冰盖被分割成快速流动的冰流，中间隔着移动较慢的冰。其次，我们的海底形态证据支持了早期的沉积学、地层学和年代学研究，即在魏氏晚期，几乎所有西部和北部斯瓦尔巴特群岛周围都有一个大冰盖到达陆架边缘。因此，认为斯瓦尔巴群岛上的冰盖相对有限，西海岸一些地区处于最后一次冰川高峰时不结冰的想法不太可能是正确的。第三，冰盖似乎从跨陆架槽和外峡湾撤退得更快，尽管有时这种情况是以接地带楔形指示的断断续续的模式发生的，而从中间的浅滩撤退的速度则更慢。此外，在距离斯瓦尔巴特群岛西北海岸10-20公里的陆架边缘绘制了冰盖的搁浅区域，这表明在魏克斯利晚期，冰没有到达邻近的耶尔马克高原。
High‐resolution bathymetric mapping of the fjords and continental shelf around the Svalbard archipelago shows an extensive pattern of large‐ and medium‐scale submarine landforms formed by differences in ice‐flow regimes. Mega‐scale glacial lineations, lateral moraines, transverse ridges and glaciotectonic features are superimposed on the large‐scale fjord, shelf and cross‐shelf trough morphology of the margin. From these landforms we have inferred the flow and dynamics of the last ice sheet on Svalbard. Major fjords and their adjacent cross‐shelf troughs have been identified as the main routes for ice streams draining the ice sheet. On the west coast of Svalbard major pathways existed along Bellsund, Isfjorden and Kongsfjorden. Along the northern Svalbard margin most of the ice drained through the Woodfjorden cross‐shelf trough and Wijdefjorden‐Hinlopen strait. Extensive areas with trough‐parallel glacial lineations in the cross‐shelf troughs suggest fast ice flow by palaeo‐ice streams. Lateral ice‐stream moraines, several tens of kilometres in length, have been mapped along the margins of some of the cross‐shelf troughs, identifying the border zone between fast ice flow and stagnant or slow‐flowing ice on intervening banks. Several general implications can be drawn from the interpretation of the glacier‐derived submarine landforms around Svalbard. Firstly, the Late Weichselian ice sheet was partitioned into fast‐flowing ice streams separated by slower moving ice. Secondly, our submarine morphological evidence supports earlier sedimentological, stratigraphical and chronological studies in implying that a large ice sheet reached the shelf edge around almost all of western and northern Svalbard in the Late Weichselian. The idea of a relatively restricted ice sheet over Svalbard, with ice‐free conditions in some areas of the west coast at the Last Glacial Maximum, is therefore unlikely to be correct. Thirdly, the ice sheet appears to have retreated more rapidly from the cross‐shelf troughs and outer fjords, although sometimes this occurred in a punctuated pattern indicated by grounding‐zone wedges, and more slowly from the intervening shallower banks. In addition, a grounding zone for the ice sheet has been mapped at the shelf edge 10–20 km off the northwest coast of Svalbard, suggesting that ice did not reach the adjacent Yermak Plateau during the Late Weichselian.