Sediment Thicknesses and Holocene Glacial Marine Sedimentation Rates in Three East Greenland Fjords (ca. 68°N)
Sediment Thicknesses and Holocene Glacial Marine Sedimentation Rates in Three East Greenland Fjords (ca. 68°N)
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三个东格陵兰峡湾（约北纬 68°）的沉积物厚度和全新世冰川海洋沉积率
DOI：
10.1086/629711
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
J. Dwyer
中科院分区：
文献类型：
--
作者：
J. Andrews;J. Milliman;A. Jennings;N. Rynes;J. Dwyer
我们比较了测量和估计的沉积物预算在东格陵兰岛严重冰川峡湾。质量平衡计算和区域冰川气候条件表明，在Kangerdlugssuaq和Nansen峡湾，流向海底的沉积物通量主要是冰山漂流，而不是融水中悬浮颗粒的降雨，因为冰川崩解通量估计为15和2美元/年，而融水体积分别为4.4和1.7美元/年。三个峡湾的重力岩心表明，最上层1-2.5米的沉积物由杂岩或细粒层压泥组成。对钙质有孔虫或贝壳（共16个）的AMS放射性碳测年表明，过去1 ka内峡湾内的沉积速率为110 - 340 cm/ka，而在内陆架和中陆架的Holecene期间为10-20 cm/ka。在Kangerdlugssuaq峡湾和海槽系统内，年沉积物排放量约为0.67美元乘以10^{6}$吨/年，这意味着全流域平均剥蚀率为0.01 mm/年（0.01 m/ka）。在东格陵兰的Kangerdlugssuaq和Nansen峡湾进行了气枪和深拖（Huntec）地震剖面测量，结果表明沉积物填充平均分别为500米和350米;它们主要由声学分层沉积物组成。如果沉积物充填物的年龄完全是全新世的，那么所需的平均沉积物累积速率为35-50 m/ka，比最近1-2 ka的C控制速率大一个数量级。这增加了峡湾沉积物可能被绕过的可能性，并不总是在冰川前进过程中回收;这将影响连续冰川作用期间邻近大陆架和深海地区的沉积速率。
We compared measured and estimated sediment budgets in heavily glaciated fjords in East Greenland. Mass balance calculations and regional glacio-climatic conditions suggest that the sediment flux to the seafloor in Kangerdlugssuaq and Nansen fjords should be dominated by iceberg rafting and not by the rain-out of suspended particulates in meltwater, as the glacier calving flux is estimated at 15 and $$2 km^{3}/yr$$, compared to meltwater volumes of 4.4 and $$1.7 km^{3}/yr$$, respectively. Gravity cores in the three fjords indicate that the uppermost 1-2.5 m of sediment consists of diamictons or fine-grained laminated muds. AMS radiocarbon dates on calcareous foramininfera or shells (16 total) indicate sedimentation rates of 110 to 340 cm/ka within the fjords over the last 1 ka, and 10-20 cm/ka during the Holecene on the inner and middle shelf. Annual sediment discharge is around $$0.67 \times 10^{6}$$ tonnes/yr within the Kangerdlugssuaq Fjord and Trough system, which translates into an average basin-wide rate of denudation of 0.01 mm/yr (0.01 m/ka). Air gun and deep-towed (Huntec) seismic profiling was carried out in Kangerdlugssuaq and Nansen fjords, East Greenland, and showed that sediment fills averaged 500 and 350 m respectively; they consist primarily of acoustically stratified sediments. If the sediment fills are entirely Holocene in age then the required average sediment accumulation rates of 35-50 m/ka are an order of magnitude larger than the $$^{14}C $$controlled rates of the last 1-2 ka. This raises the possibility that fjord sediments may be by-passed and not always recycled during glacial advances; this will affect sedimentation rates on adjacent shelves and deep-sea areas during successive glaciations.