Permafrost history in Arctic Siberia - insights from the cryogenic weathering record at Elgygytgyn crater, NE Siberia

这项建议侧重于确定北极西伯利亚永久冻土条件变化所表现出的气候变化。特别令人感兴趣的是建立了一种沉积学方法，可以通过地质时间估计低温风化程度和古土壤温度。这项研究探索了东北西伯利亚Elgytgyn火山口湖的湖泊沉积物记录，跨越了过去30万年，目前代表着北极最长的陆地古气候和环境档案。从集水区提取的跨越过去14,000年的短永久冻土岩心的样本，以及一套代表现代条件的地表样本将被用作参考。将研究下列被认为反映东北西伯利亚冰缘长期动力学的沉积物矿物学性质：(1)选定粒度组分中的石英与长石的比率提供了反映霜冻风化程度的指标；(2)将对颗粒的扫描电子显微镜进行图像分析，以量化冰冻风化所产生的石英颗粒形态和表面特征；(3)重矿物将被用作物源指标，以确定源岩成分和低温碎屑的变化。这些结果为通过北西伯利亚北极第四纪冰川旋回确定永久冻土条件的强度提供了一个基本工具。这是ICDP资助的深井钻探未来核心研究的概念性成果。

This proposal focusses on determining climate variations as expressed in variations of permafrost conditions in Arctic Siberia. Of particular interest is the establishment of a sedimentological method that allows estimating the degree of cryogenic weathering and palaeo soil temperatures through geologic time. The study explores a lake sediment record from Elgygytgyn crater lake, NE Siberia, spanning the last 300,000 years and currently representing the longest terrestrial palaeoclimate and -environment archive for the Arctic. Samples from short permafrost cores extracted in the catchment and spanning the last 14,000 years and a set of surface samples that represent modern conditions will be used as a reference. The following sediment-mineralogical properties, which are considered to mirror long term periglacial dynamics in NE Siberia, will be studied: (1) the ratio of quartz to feldspar in selected grain size fractions provides an indicator reflecting the degree of frost weathering; (2) image analysis of scanning electron micrographs of particles will be performed to yield a quantification of quartz grain morphology and surface features stemming from frost weathering; (3) heavy minerals will be used as provenance indicators to define changes in source rock composition and cryogenic detritus. The results prepare a fundamental tool that allows determining the intensity of permafrost conditions through Quaternary glacial cycles in the North Siberian Arctic. This is a conceptual outcome of future core studies from ICDP funded deep drillings.