Retreat of the Smith Sound Ice Stream in the Early Holocene
Retreat of the Smith Sound Ice Stream in the Early Holocene
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DOI：
10.1111/bor.12391
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发表时间：
2019-10-01
期刊：
影响因子：
2.2
通讯作者：
Mix, Alan
中科院分区：
文献类型：
--
作者：
Jennings, Anne E.;Andrews, John T.;Mix, Alan
纳尔斯海峡是北冰洋和巴芬湾之间的主要连接，在上一次冰川期间被合并的伊努提斯冰盖和格陵兰冰盖堵塞。本文重点研究了导致海峡开放的事件和过程，以及北极-大西洋直通流建立后的环境响应。这项研究是基于对巴芬湾北部2001LSSL-0014PC和TC岩芯的沉积学、矿物学和有孔虫分析。用Delta R=220+/-20年标定了底栖有孔虫的放射性碳测年。基面致密的卵石泥被解释为冰川覆盖松散的海洋沉积物而形成的冰下沉积。它被近冰(红色/灰色层状冰缘单元，无有孔虫，包含2毫米碎屑，解释为冰排碎屑)到远冰(钙质灰色卵石泥和有孔虫指示分层水柱，具有冷却的大西洋水动物和与多年生和季节性海冰覆盖有关的物种)冰海沉积单元覆盖。年龄模型显示，冰川最早在公元11.7年退缩到史密斯湾，最晚在公元11.2年。Ka BP之后，随着冰缘向肯尼迪海峡撤退，冰川条件逐渐变得更加遥远。我们假设在9.3和9.9(9.4-8.9 1西格玛)卡之间沉积了一个明显的IRD层。Ka BP标志着肯尼迪海峡冰的破裂，导致纳尔斯海峡作为北极-大西洋直通流的开放。覆盖的有孔虫组合表明，随着营养丰富的北极表层水的进入，海洋生产力得到了增强。粘性有孔虫和砂粒大小的硅藻的显著增加以及碎屑方解石的丧失是最上层的生物扰动泥浆的特征，它是在4.8(3.67-5.55 1西格玛)卡之后沉积的。Ka BP。这一转变的时机没有得到很好的解决，因为它与冰缘退回陆地后随之而来的缓慢沉积速度不谋而合。
Nares Strait, a major connection between the Arctic Ocean and Baffin Bay, was blocked by coalescent Innuitian and Greenland ice sheets during the last glaciation. This paper focuses on the events and processes leading to the opening of the strait and the environmental response to establishment of the Arctic-Atlantic throughflow. The study is based on sedimentological, mineralogical and foraminiferal analyses of radiocarbon-dated cores 2001LSSL-0014PC and TC from northern Baffin Bay. Radiocarbon dates on benthic foraminifera were calibrated with Delta R = 220 +/- 20 years. Basal compact pebbly mud is interpreted as a subglacial deposit formed by glacial overriding of unconsolidated marine sediments. It is overlain by ice-proximal (red/grey laminated, ice-proximal glaciomarine unit barren of foraminifera and containing >2 mm clasts interpreted as ice-rafted debris) to ice-distal (calcareous, grey pebbly mud with foraminifera indicative of a stratified water column with chilled Atlantic Water fauna and species associated with perennial and then seasonal sea ice cover) glacial marine sediment units. The age model indicates ice retreat into Smith Sound as early as c. 11.7 and as late as c. 11.2 cal. ka BP followed by progressively more distal glaciomarine conditions as the ice margin retreated toward the Kennedy Channel. We hypothesize that a distinct IRD layer deposited between 9.3 and 9 (9.4-8.9 1 sigma) cal. ka BP marks the break-up of ice in Kennedy Channel resulting in the opening of Nares Strait as an Arctic-Atlantic throughflow. Overlying foraminiferal assemblages indicate enhanced marine productivity consistent with entry of nutrient-rich Arctic Surface Water. A pronounced rise in agglutinated foraminifers and sand-sized diatoms, and loss of detrital calcite characterize the uppermost bioturbated mud, which was deposited after 4.8 (3.67-5.55 1 sigma) cal. ka BP. The timing of the transition is poorly resolved as it coincides with the slow sedimentation rates that ensued after the ice margins retreated onto land.