Late Quaternary deposition of ice-rafted sand in the subpolar North Atlantic (lat 40° to 65°N)
Late Quaternary deposition of ice-rafted sand in the subpolar North Atlantic (lat 40° to 65°N)
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DOI：
10.1130/0016-7606(1977)88
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发表时间：
1977-12
影响因子：
4.9
通讯作者：
W. Ruddiman
中科院分区：
文献类型：
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作者：
W. Ruddiman
在最后一次间冰期-冰期循环期间，北大西洋冰筏沉积模式的一个重大变化发生在大约75，000 B. P.。在此之前，同位素阶段5期间近50，000年的沉积在格陵兰岛和纽芬兰岛附近的西北部最大。主要的冰川模式是非常不同的;主沉积轴突然转移到纬向轴沿着46°到50°N，反映了冰的通道远离极点之前到达足够温暖的水融化。在主乌尔姆冰期期间，这种模式在65,000年里基本上保持不变。除了沿沿着50°N增加了一个集中的东向分量外，最好用现代洋流的类比来解释间冰期沉积的峰值模式。逆时针流动也能很好地解释冰川模式。从拉布拉多海进入北大西洋西部的劳伦泰德和格陵兰冰向东和东南方向移动，直接进入冰川沉积最大值。斯堪的纳维亚半岛的冰在挪威附近放下了部分底床负荷，在冰岛以南以逆时针方向向西南方向进入北大西洋，最后沿着主要的沉积最大值融化。冰筏沉积物向大西洋和挪威海的总输入速率在115，000 B. P.（冰期开始）时略有增加，在75，000 B. P.（主要冰期过渡）时显著上升，并在乌尔姆晚期继续上升，直至晚冰期最大值。因此，北大西洋冰筏沉积与冰盖大小呈正相关。在第四纪，世界海洋中约70%的大陆碎屑冰筏沉积发生在冰岛以南的北大西洋亚极地。在过去的300万年里，仅通过冰筏漂流，估计就有20万立方公里的湿的松散漂流物从大陆移动到大西洋深处。这相当于在被认为是向北大西洋提供冰筏碎屑的大陆的所有部分上覆盖了一层16米厚的漂流物。
A major change in the North Atlantic pattern of ice-rafting deposition, during the last interglacial-glacial cycle, occurred approximately 75,000 B.P. Prior to this time, deposition for a period of almost 50,000 yr during isotopic stage 5 was greatest in the northwest near Greenland and Newfoundland. The main glacial pattern was very different; the main depositional axis shifted abruptly to a zonal axis along lat 46° to 50°N, reflecting the passage of ice farther from the pole before reaching water warm enough in which to melt. This pattern remained essentially unchanged for 65,000 yr during the main Wurm glaciation. The peak interglacial depositional pattern can best be explained by analogy with the modern oceanic flow, except for the addition of a concentrated eastward component along lat 50°N. The glacial pattern is also best explained by counterclockwise flow. Laurentide and Greenlandic ice entering the western North Atlantic from the Labrador Sea moved to the east and southeast directly into the glacial depositional maximum. Scandinavian ice dropped part of its bed load near Norway, looped to the southwest into the North Atlantic in a counterclockwise passage south of Iceland, and finally melted along the primary depositional maximum. Total input rates of ice-rafted sediment to the Atlantic and Norwegian Sea increased slightly at 115,000 B.P. (the glacial inception), rose markedly at 75,000 B.P. (the major glacial transition), and continued to rise late in the Wurm toward the late-glacial maximum. North Atlantic ice-rafting deposition is thus positively correlated with ice-sheet size. During Quaternary time, roughly 70% of ice-rafted deposition of continental detritus in the world9s oceans has occurred in the subpolar North Atlantic south of Iceland. During the past 3 m.y., a mass of wet unconsolidated drift estimated at 200,000 km 3 has been moved from the continents to the deep Atlantic by ice-rafting alone. This is equivalent to a layer of drift 16 m thick over all parts of the continents thought to have supplied ice-rafted detritus to the North Atlantic.