Chronology and sedimentology of a new 2.9 ka annually laminated record from South Sawtooth Lake, Ellesmere Island
Chronology and sedimentology of a new 2.9 ka annually laminated record from South Sawtooth Lake, Ellesmere Island
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埃尔斯米尔岛南锯齿湖新的 2.9 ka 年层压记录的年代学和沉积学
DOI：
10.1016/j.quascirev.2019.105875
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发表时间：
2019
影响因子：
4
通讯作者：
St-Onge, Guillaume
中科院分区：
文献类型：
--
作者：
Lapointe, Francois;Francus, Pierre;Stoner, Joseph S.;Abbott, Mark B.;Balascio, Nicholas L.;Cook, Timothty L.;Bradley, Raymond S.;Forman, Steven L.;Besonen, Mark;St-Onge, Guillaume
北极地区存在的年际叠层湖泊记录很少，但需要这些高分辨率的气候档案来更好地了解这个敏感地区的气候突变和气候变率的自然模式。本文介绍了埃尔斯米尔岛福斯海姆半岛2900年的高分辨率湖泊沉积记录。该年代学是基于重叠沉积物薄片的高分辨率扫描电镜图像上的多次年代学，并得到了几种独立测年技术的支持，包括137cs和210pb分析，位于复合层序底部的一个光学刺激发光年龄，以及该记录与最长的高北极年代学记录（下默里湖）的古地磁变化的比较。这证实了锯齿年表的可靠性。在扫描电子显微镜（SEM）下检查的高分辨率后向散射图像对于提供湖泊沉积过程的更详细视图至关重要，因此有助于比传统图像分析更精确地描绘varves。精细尺度地球化学分析表明，湖泊沉积以碎屑沉积为主，元素地球化学受粒度影响。多代主成分分析和South Sawtooth Lake粗粒度分数的波动与附近的Agassiz冰帽∂18O记录相似，包括在小冰期寒冷期的较低值。这些结果表明，新的高分辨率连续记录具有可靠的阀门年表，对温度变化敏感。南锯齿湖的平均沉积速率为1.67 mm a - 1，高于北极地区的任何其他沉积序列，为提取新的、高分辨率的古气候和古环境记录提供了独特的机会，而该地区目前几乎没有其他记录。
Few annually laminated (varved) lacustrine records exist in the Arctic, but these high-resolution climate archives are needed to better understand abrupt climate change and the natural mode of climate variability of this sensitive region. This paper presents a new high-resolution 2900-year long varved lake sediment record from the Fosheim Peninsula, Ellesmere Island. The varve chronology is based on multiple varve counts made on high-resolution scanning electron microscope images of overlapping sediment thin sections, and is supported by several independent dating techniques, including137Cs and210Pb analysis, one optically stimulated luminescence age located close to the bottom of the composite sequence, and comparison between paleomagnetic variations of this record and the longest High-Arctic varve record, Lower Murray Lake, which confirms the reliability of the Sawtooth chronology. High-resolution backscattered images examined under a scanning electron microscope (SEM) were crucial to giving a more detailed view of sedimentation processes in the lake and thus help to delineate varves more precisely than in conventional image analysis. Fine-scale geochemical analysis reveals that lake sedimentation is mainly clastic and that elemental geochemistry is influenced by grain-size. Principal component analysis of multiple proxies and the coarse grain-size fraction of South Sawtooth Lake display similar fluctuations to the nearby Agassiz Ice Cap ∂18O record, including lower values during the Little Ice Age cold period. These results show this new high-resolution and continuous record has a reliable varve chronology and is sensitive to temperature variability. South Sawtooth Lake's mean sedimentation rate of 1.67 mm a−1is higher than any other sedimentary sequence in the High Arctic providing a unique opportunity for extracting new, high-resolution paleoclimatological and paleoenvironmental record in a region where few other records currently exist.