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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Sedimentary processes at ice sheet grounding-zone wedges revealed by outcrops, Washington State (USA)
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Sedimentary processes at ice sheet grounding-zone wedges revealed by outcrops, Washington State (USA)

机译：冰盖接地区楔形裂缝的沉积过程露头，华盛顿州（美国）透露

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摘要

Grounding-zone wedges (GZWs) mark the grounding terminus of flowing marine-based ice streams and, in the presence of an ice shelf, the transition from grounded ice to floating ice. The morphology and stratigraphy of GZWs is predominantly constrained by seafloor bathymetry, seismic data, and sediment cores from deglaciated continental shelves; however, due to minimal constraints on GZW sedimentation processes, there remains a general lack of knowledge concerning the production of these landforms. Herein, outcrop observations are provided of GZWs from Whidbey Island in the Puget Lowlands (Washington State, USA). These features are characterized by prograded diamictons bounded by glacial unconformities, whereby the lower unconformity indicates glacial advance of the southern Cordilleran Ice Sheet and the upper unconformity indicates locally restricted ice advance during GZW growth; the consistent presence of an upper unconformity supports the hypothesis that GZWs facilitate ice advance during landform construction. Based on outcrop stratigraphy, GZW construction is dominated by sediment transport of deformation till and melt-out of entrained basal debris at the grounding line. This material may be subsequently remobilized by debris flows. Additionally, there is evidence for subglacial meltwater discharge at the grounding line, as well as rhythmically bedded silt and sand, indicating possible tidal pumping at the grounding line. A series of GZWs on Whidbey Island provides evidence of punctuated ice sheet movement during retreat, rather than a rapid ice sheet lift-off. The distance between adjacent GZWs of 10(2)-10(3) m and the consistency in their size relative to modern ice stream grounding lines suggests that individual wedges formed over decades to centuries. (c) 2018 John Wiley & Sons, Ltd.
机译：接地区楔（GZW）标志着流动的海洋冰流的接地末端，并且在冰架存在下，从接地冰到浮冰的过渡。 GZWS的形态和地层主要受海底沐浴浴，地震数据和来自未曝光的大陆架子的沉积物核心的限制;然而，由于GZW沉积过程的限制性最小，仍然存在关于这些地形生产的普遍缺乏知识。在此，从Puget Lemlands（华盛顿州，美国华盛顿州）的Whidbey岛提供GZWS的露天观察。这些特征的特征在于由冰川不整合限定的促射线直径，由此较低的无关表示南部Cortillan冰盖的冰川进步，上部无关表示在GZW生长期间局部限制冰进步;上部不整合的一致存在支持GZW在地形结构期间促进冰的假设。基于露头地层，GZW施工是由沉积物传输的沉积物传输，并在接地线上夹带的基础碎屑融化。随后可以通过碎屑流反馈该材料。另外，有证据表明在接地线上的底纤维熔融水排放，以及节奏的嵌入式淤泥和砂，表示在接地线上可能的潮汐泵送。在Whidbey岛上的一系列GZWS提供了在撤退期间的标点冰板运动的证据，而不是快速的冰盖剥离。相对于现代冰流接地线的相邻GZW的距离和其尺寸的一致性表明，几十多年来的各个楔形形成。 （c）2018 John Wiley＆Sons，Ltd。

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