Temperate Glacimarine Varves: An Example from Disenchantment Bay, Southern Alaska
Temperate Glacimarine Varves: An Example from Disenchantment Bay, Southern Alaska
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温带冰川藻：阿拉斯加南部幻灭湾的一个例子
DOI：
10.1306/d42685c7-2b26-11d7-8648000102c1865d
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发表时间：
1997
影响因子：
2
通讯作者：
Jeffrey N. Pitcher
中科院分区：
文献类型：
--
作者：
E. Cowan;Jinkui Cai;R. Powell;Jenifer Clark;Jeffrey N. Pitcher
阿拉斯加南部的祛魅湾（Disenchantment Bay）是一个大型的海洋冰解湾，其沉积记录中包含着独特的年沉积。每年，冰川形成一对由碎屑丰富的层状到大量的杂岩在冬季由激烈的冰山漂流沉积而成，在夏季由薄层泥和浊积砂床的融水存款沉积而成。虽然全年都有冰山漂流活动，但由于融水排放的细沉积物很少，加上冬季峡湾环流和气象因素导致冰山在海湾停留的时间较长，因此粗碎屑沉积的浓度很高，仅在冬季形成二聚体。当融水在夏季开始排放时，沉积了带有坠石的层状泥。春季和秋季的条件记录了冬季和夏季之间的过渡阶段的碎屑贫diamictons。从纹层厚度计算的平均沉积物积累速率范围从48厘米/年，3.4公里，从哈伯德冰川在海湾的头部，到14厘米/年，15公里远。沉积物积累速率估计从210铅定年的核心沉积物是在同一范围内。沉积物从1986年罗素峡湾爆发洪水确定从异常高的210铅活动的沉积物表明替代沉积物来源的祛魅湾。冰海纹是一种测年工具，用于测定通常沉积在崩解冰川末端附近的贫瘠近端沉积物。它们产生古气候信息，因为它们是海洋中冰川冰和层状沉积物的产物，这些沉积物是在温带至亚极地气候中发现的大量融水排放而沉积的。
ABSTRACT The sediment record of Disenchantment Bay, Southern Alaska, a large marine calving embayment, contains distinctive annual deposits. Each year a glacimarine couplet forms with a clast-rich stratified to massive diamicton deposited in winter by intense iceberg rafting and a summer, meltwater deposit of thinly laminated mud and turbidite sand beds. Although iceberg rafting occurs throughout the year, coarse debris is deposited in high concentrations and forms diamicton only during the winter because of minimal fine sediment from meltwater discharges and a longer residence time of icebergs in the Bay due to winter fjord circulation and meteorological factors. When meltwater discharge commences in summer, laminated mud with dropstones is deposited. Spring and fall conditions are recorded a transitional phases between winter and summer by clast-poor diamictons. Average sediment accumulation rates calculated from varve thicknesses range from 48 cm/yr, 3.4 km from Hubbard Glacier at the head of the Bay, to 14 cm/yr, 15 km away. Sediment accumulation rates estimated from 210Pb dating of core sediments are in the same range. Deposits from the 1986 Russell Fiord outburst flood are identified from anomalously high 210Pb activities in sediments indicating an alternative sediment source to Disenchantment Bay. Glacimarine varves are a dating tool for the barren proximal sediments commonly deposited near calving glacier termini. They yield paleoclimatic information because they are a product of both glacial ice in the sea and laminated sediments deposited from significant melt-water discharge found in a temperate to subpolar climate.