Late Quaternary ice flow in a West Greenland fjord and cross-shelf trough system: submarine landforms from Rink Isbrae to Uummannaq shelf and slope
Late Quaternary ice flow in a West Greenland fjord and cross-shelf trough system: submarine landforms from Rink Isbrae to Uummannaq shelf and slope
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DOI：
10.1016/j.quascirev.2013.09.007
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发表时间：
2014-05-15
影响因子：
4
通讯作者：
Noormets, R.
中科院分区：
文献类型：
--
作者：
Dowdeswell, J. A.;Hogan, K. A.;Noormets, R.
海底地貌和声学地层记录允许解释格陵兰冰盖（Rink Isbrae）向西排放的冰流的过去形式和流动。上新世晚期-更新世冰川包有几百米厚，向下覆盖在中新世上部的地平线上。根据400公里长的Uummannaq峡湾-陆棚-斜坡系统的海底剖面仪记录绘制了几个声相。声学分层相覆盖了峡湾和槽底的大部分，解释为冰川沉积物从浑浊的融水中的细粒碎屑的雨出。在这一渐变之下是一个半透明的变形-耕作单元，其中包括被掩埋的流线型地貌。Uummannaq系统的地貌分布被用来重建过去的冰的范围和流动方向。流线型地貌（大规模冰川线理，鼓，峭壁和尾巴）的存在表明，冰流先进通过峡湾系统，以填补Uummannaq槽，达到在末次冰期最大的陆架边缘。在海槽之外，有一个主要由冰川碎屑流形成的大扇。在Uummannaq Fan上没有观察到浊流通道，而在以南300公里处的Disko Fan上则有发达的通道。冰的退却在距今14.8万年前就开始了。Uummannaq海槽的接地带楔（GZW）意味着撤退是偶发性的，被几个静止的站立打断。GZW之间的冰退缩可能相对较快。除了一个标志着小冰期最大位置的主要冰碛脊外，几乎没有沉积物证据表明峡湾内部仍然存在。在乌曼纳格海槽两侧的浅滩上，冰山的犁削已经重塑了早期冰盖活动的任何形态学证据。(C)2013作者由爱思唯尔有限公司出版。保留所有权利。
Sea-floor landforms and acoustic-stratigraphic records allow interpretation of the past form and flow of a westward-draining ice stream of the Greenland Ice Sheet, Rink Isbrae. The Late Pliocene-Pleistocene glacial package is several hundred metres thick and down-laps onto an upper Miocene horizon. Several acoustic fades are mapped from sub-bottom profiler records of the 400 km-long Uummannaq fjord-shelf-slope system. An acoustically stratified facies covers much of the fjord and trough floor, interpreted as glacimarine sediment from rain-out of fine-grained debris in turbid meltwater. Beneath this fades is a semi-transparent deformation-till unit, which includes buried streamlined landforms. Land-form distribution in the Uummannaq system is used to reconstruct past ice extent and flow directions. The presence of streamlined landforms (mega-scale glacial lineations, drumlins, crag-and-tails) shows that an ice stream advanced through the fjord system to fill Uummannaq Trough, reaching the shelf edge at the Last Glacial Maximum. Beyond the trough there is a major fan built mainly of glacigenic debris flows. Turbidity-current channels were not observed on Uummannaq Fan, contrasting with well-developed channels on Disko Fan, 300 km to the south. Ice retreat had begun by 14.8 cal. ka ago. Grounding-zone wedges (GZW) in Uummannaq Trough imply that retreat was episodic, punctuated by several still-stands. Ice retreat between GZWs may have been relatively rapid. There is little sedimentary evidence for still-stands in the inner fjords, except for a major moraine ridge marking a Little Ice Age maximum position. On the shallow banks either side of Uummannaq Trough, iceberg ploughing has reworked any morphological evidence of earlier ice-sheet activity. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.