Signature of ice streaming in Bjornoyrenna, Polar North Atlantic, through the Pleistocene and implications for ice-stream dynamics

被引:53
作者
Andreassen, Karin [1 ]
Winsborrow, Monica [1 ]
机构
[1] Univ Tromso, Dept Geol, NO-9037 Tromso, Norway
关键词
WESTERN BARENTS SEA; TROUGH-MOUTH FANS; CENOZOIC EVOLUTION; SVALBARD MARGIN; SHEET; SEDIMENTS; GEOMORPHOLOGY; ANTARCTICA; STABILITY;
D O I
10.3189/172756409789624238
中图分类号
P9 [自然地理学];
学科分类号
0705 ; 070501 ;
摘要
The geomorphology of palaeo-ice-stream beds and the internal structure of underlying tills can provide important information about the subglacial conditions during periods of fast flow and quiescence. This paper presents observations from three-dimensional seismic data, revealing the geomorphology of buried beds of the Bjornoyrenna (Bear Island Trough) ice stream, the main drainage outlet of the former Barents Sea ice sheet. Repeated changes in ice dynamics are inferred from the observed successions of geomorphic features. Megablocks, aligned in long chains parallel to inferred ice-stream flowlines, and forming dipping plates that are thrust one on top of another, are taken as evidence for conditions of compressive ice flow. Mega-scale glacial lineations (MSGL) and pull-apart of underlying sediment blocks suggest extensional flow. The observed pattern of megablocks and rafts overprinted by MSGL indicates a change in ice dynamics from a compressional to an extensional flow regime. Till stiffening, due to subglacial freezing, is the favoured mechanism for creating switches in sub-ice-stream conditions. The observed pattern of geomorphic features indicates that periods of slowdown or quiescence were commonly followed by reactivation and fast flow during several glaciations, suggesting that this may be a common behaviour of marine ice streams.
引用
收藏
页码:17 / 26
页数:10
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