Baffin Bay paleoenvironments in the LGM and HS1: Resolving the ice-shelf question
Baffin Bay paleoenvironments in the LGM and HS1: Resolving the ice-shelf question
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DOI：
10.1016/j.margeo.2017.09.002
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发表时间：
2017-09
期刊：
影响因子：
2.9
通讯作者：
Marine Geology Elsevier;A. Jennings;J. Andrews;C. Ó. Cofaigh;G. St‐Onge;S. Belt;Patricia Cabedo-Sanz;C. Pearce;C. Hillaire‐Marcel;D. C. Campbell
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作者：
Marine Geology Elsevier;A. Jennings;J. Andrews;C. Ó. Cofaigh;G. St‐Onge;S. Belt;Patricia Cabedo-Sanz;C. Pearce;C. Hillaire‐Marcel;D. C. Campbell
来自西格陵兰大陆斜坡中部Disko槽口扇的核心HU 2008029 - 12 PC用于测试在末次盛冰期（LGM）和冰消期开始时是否有冰架覆盖巴芬湾。我们使用底栖和浮游有孔虫组合，稳定同位素分析的浮游有孔虫，藻类生物标志物，冰筏碎屑（IRD），从CT扫描定义的岩相特征，和定量矿物学重建古海洋条件，沉积过程和沉积物来源。年表基于南极有孔虫的放射性碳年代，使用140 ± 3014 C年的BRR，辅以Stern和Lisiecki（2013）的不同储层估计，提供了潜在年龄的包络。HU 2008029 - 12 PC在整个过程中进行生物扰动。在11.3米和4.6米（末次冰期至HS 1）的岩芯基底之间的沉积物包括薄浊积岩、羽毛岩和半远洋沉积物，格陵兰的物源与格陵兰冰盖边缘或靠近大陆架边缘的活动过程一致。浮游有孔虫的栖息地尖峰与底栖有孔虫的丰度升高相吻合，表明大西洋冷水、融水和间歇性海洋生产力的组合。IRD和IP 25在这段时间内很少见，但在LGM期间，作为海洋生产力指标的油菜甾醇达到并维持在低水平。这些生物特征与海冰覆盖的海洋经历更多开放水域的时期是一致的，例如海冰覆盖中的铅或冰穴，在深处有冰冷的大西洋水，而不是完全的冰架覆盖。他们不支持存在一个完整的巴芬湾冰架覆盖从戴维斯海峡的地面冰延伸。最初的冰从西格陵兰边缘撤退表现为一个明显的岩相转变为生物扰动，淤泥质泥与罕见的格陵兰起源的IRD在467厘米（16.2 cal ka BP; IRD = 140年）内HS 1。有孔虫丰度和海洋温暖指标底栖有孔虫的峰值出现在冰从大陆架边缘开始退缩之前。在HS 1，IP 25，油菜甾醇和底栖有孔虫表明海冰边缘生产力增加，表明变暖interstadial条件结束。在Bølling/Allerød interstadial内，IP 25含量的强烈上升和富含北方巴芬湾碎屑碳酸盐的IRD尖峰表明，北方巴芬湾冰流正在退缩，并为开放水域增加、西格陵兰海流中大西洋水的平流以及沿西格陵兰沿着IRD带的形成提供了证据。格陵兰边缘。
Core HU2008029-12PC from the Disko trough mouth fan on the central West Greenland continental slope is used to test whether an ice shelf covered Baffin Bay during the Last Glacial Maximum (LGM) and at the onset of the deglaciation. We use benthic and planktic foraminiferal assemblages, stable isotope analysis of planktic forams, algal biomarkers, ice-rafted detritus (IRD), lithofacies characteristics defined from CT scans, and quantitative mineralogy to reconstruct paleoceanographic conditions, sediment processes and sediment provenance. The chronology is based on radiocarbon dates on planktic foraminifers using a ∆ R of 140 ± 3014C years, supplemented by the varying reservoir estimates of Stern and Lisiecki (2013) that provide an envelope of potential ages. HU2008029-12PC is bioturbated throughout. Sediments between the core base at 11.3 m and 4.6 m (LGM through HS1) comprise thin turbidites, plumites and hemipelagic sediments with Greenlandic provenance consistent with processes active at the Greenland Ice Sheet margin grounded at or near the shelf edge. Abundance spikes of planktic forams coincide with elevated abundance of benthic forams in assemblages indicative of chilled Atlantic Water, meltwater and intermittent marine productivity. IRD and IP25are rare in this interval, but brassicasterol, an indicator of marine productivity reaches and sustains low levels during the LGM. These biological characteristics are consistent with a sea-ice covered ocean experiencing periods of more open water such as leads or polynyas in the sea ice cover, with chilled Atlantic Water at depth, rather than full ice-shelf cover. They do not support the existence of a full Baffin Bay ice shelf cover extending from grounded ice on the Davis Strait. Initial ice retreat from the West Greenland margin is manifested by a pronounced lithofacies shift to bioturbated, diatomaceous mud with rare IRD of Greenlandic origin at 467 cm (16.2 cal ka BP; ∆ R = 140 yrs) within HS1. A spike in foraminiferal abundance and ocean warmth indicator benthic forams precedes the initial ice retreat from the shelf edge. At the end of HS1, IP25, brassicasterol and benthic forams indicative of sea-ice edge productivity increase, indicating warming interstadial conditions. Within the Bølling/Allerød interstadial a strong rise in IP25content and IRD spikes rich in detrital carbonate from northern Baffin Bay indicate that northern Baffin Bay ice streams were retreating and provides evidence for increased open water, advection of Atlantic Water in the West Greenland Current, and formation of an IRD belt along the W. Greenland margin.