Identifying fast ice flow from landform assemblages in the geological record: a discussion
Identifying fast ice flow from landform assemblages in the geological record: a discussion
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从地质记录中的地貌组合中识别快速冰流：讨论
DOI：
10.3189/172756499781821887
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发表时间：
1999
影响因子：
2.9
通讯作者：
J. Hart
中科院分区：
文献类型：
--
作者：
J. Hart
本文简要讨论了山谷冰川（涌动冰川、间歇冰川和变形床冰川）和冰盖（冰流和变形床冰盖流）中不同类型的快速冰流（包括空间和时间）。虽然不太可能有任何特定的个别地貌与快速冰流，可能有地貌组合。在山谷冰川规模上，认为存在两种地貌组合：（1）冰冲类型，以推平推冰碛和丘状冰碛为主（与冰上沉积物供应量高的冰川、粗粒基质和粗粒冰前沉积物楔有关）;（2）以“挤压”推碛、凹槽和鼓丘为主的床流类型（与冰上沉积物供应量低和细粒基底的冰川有关）。冰逆冲流类型仅与不连续的快速流动（在刚性和变形床上）有关;而床流类型与连续和不连续的快速流动有关。这两种地貌组合也可能是冰盖尺度快速冰流的指示，特别是床流类型。如果是这样的话，那么不连续的快速冰流可能是由冰冲地貌组合和床流的风格，其中鼓的存在。它还建议，冰流的具体证据包括独特的地貌组合内的山谷或扇形的位置，和一个可预测的模式，反映了速度的drumlin伸长率。
Abstract Different types of fast ice flow (both spatial and temporal) in valley glaciers (surging glaciers, tidewater glaciers and deforming-bed glaciers) and ice sheets (ice streams and deforming-bed ice-sheet flow) are discussed briefly. Although there are unlikely to be any specific individual landforms associated with fast ice flow, there may be landform assemblages. At valley glacier scale, it is suggested that there are two landform assemblages: (1) an ice-thrust type, dominated by bulldozed push moraines and hummocky moraines (associated with glaciers with a high supraglacial sediment supply, a coarse-grained substrate and a coarse-grained proglacial sediment wedge); and (2) a bed-flow type dominated by “squeeze” push moraines, flutes and drumlins (associated with glaciers with a low supra- glacial sediment supply and fine-grained substrate). The ice-thrust type alone is only associated with discontinuous fast flow (on both rigid and deforming beds); whilst the bed-flow type is associated with both continuous and discontinuous fast flow. It is suggested that these two landform assemblages may also be indicative of fast ice flow at ice-sheet scale, in particular the bed-flow style. If that is the case, then discontinuous fast ice flow may be indicated by the ice-thrust landform assemblage and the bed-flow style where drumlins are present. It is also suggested that specific evidence for ice streams includes the distinctive land-form assemblages within valley or fan-like locations, and a predictable pattern of velocity reflected by drumlin elongation ratios.