Solifluction Lobes as Potential Sediment Contributors to Linnévatnet Spitsbergen Svalbard, 2013

As global changes become more pronounced, arctic regions are increasingly significant in climate studies due to their sensitivity and rapid response to the environment. Svalbard, an arctic archipelago located at 78°N, provides ideal subjects for studying climate history and the impacts of climate change given the abundance of glaciers and continuous permafrost. This study was conducted in western Spitsbergen, Svalbard, as part of a larger project examining climate and sedimentation in the Linnédalen glacio-fluvial-lacustrine system. Sedimentation records in such environments can serve as important proxies of past climate as well as indicators of current climate change, particularly in the preservation of varves. However, in order to interpret such sedimentation patterns, both primary and secondary sources of sediment must be characterized. Soliflucting lobes of relict marine terraces around Linnévatnet were examined and compared to lake cores to identify their potential sediment contribution. This potential input was investigated by mapping the shoreline, deploying short-term sediment traps for the summer 2012 field season, collecting 13 source grab samples, and extracting 5 lake cores. Sieve and laser grain-size analyses were performed on the source samples to further characterize the potential sources. The mineralogical compositions of the lake cores and source samples were analyzed using X-ray diffraction. The grain-size results point to the common original glacio-marine-fjord deposition in this dynamic setting with many sediment inputs. The similar grain-size distributions seen in solifluction samples not only reveal the valley-wide feature of the absence of medium sand(1 to 2φor 0.5 to 0.25 mm), but also help explain the lack of mineralogical variation among the clay fractions of source samples. Variations among the clay fraction of source samples (the fraction potentially reaching lake cores) are observed in the relative abundances of chlorite and illite and appear to reflect proximal bedrock sources. However, these differences do not visibly translate to the 5 lake cores, and all cores maintain similar chlorite:illite ratios, preventing a quantitative assessment of how much each potential source is contributing to the lake cores or whether the solifluction sources are significantly impacting varve analyses.随着全球变化日益显著，北极地区因其对环境的敏感性和快速响应性，在气候研究中的重要性与日俱增。位于北纬78°的北极群岛斯瓦尔巴群岛（Svalbard）拥有大量冰川与连续多年冻土，是研究气候历史及气候变化影响的理想研究区域。本研究于斯瓦尔巴群岛的斯匹次卑尔根岛西部开展，属于Linnédalen冰缘-河流-湖相系统（glacio-fluvial-lacustrine system）气候与沉积作用大型研究项目的一部分。此类环境中的沉积记录可作为过去气候的重要代用指标，同时也是当前气候变化的指示物，在纹泥（varves）的保存方面尤为如此。然而，要解释此类沉积模式，必须对沉积物的原生与次生来源进行表征。研究人员对Linnévatnet周边残余海阶的泥流舌（soliflucting lobes）进行了考察，并与湖芯样本对比，以明确其潜在的沉积物贡献。为调查这一潜在输入，研究团队完成了以下工作：绘制海岸线分布图、在2012年夏季野外季部署短期沉积物捕集器（sediment traps）、采集13份源区抓取沉积物样本（grab samples），以及获取5根湖芯。对源区样本开展筛分与激光粒度分析，以进一步表征潜在沉积物来源。利用X射线衍射（X-ray diffraction）分析了湖芯与源区样本的矿物组成。粒度分析结果显示，在这一存在多种沉积物输入的动态环境中，普遍存在原生冰缘-海相-峡湾沉积（glacio-marine-fjord deposition）。泥流样本中相似的粒度分布特征，不仅揭示了整个流域缺乏中砂（1~2φ或0.5~0.25mm）的现象，还有助于解释源区样本黏土级组分间矿物学差异缺失的原因。源区样本的黏土级组分（该组分可能进入湖芯）的相对丰度存在变化，表现为绿泥石（chlorite）与伊利石（illite）的占比差异，这似乎反映了近端基岩来源的影响。然而，这些差异并未在5根湖芯中体现，所有湖芯均保持相近的绿泥石:伊利石比值，因此无法定量评估各潜在来源对湖芯的贡献比例，也无法判断泥流来源是否对纹泥分析产生了显著影响。