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

这项建议的重点是确定北极西伯利亚永久冻土条件变化所表达的气候变化。特别令人感兴趣的是建立一种沉积学方法，可以估计地质时期的低温风化程度和古土壤温度。该研究探索了西伯利亚东北部Elgygytgyn火山口湖的湖泊沉积物记录，该记录跨越了过去30万年，是目前北极最长的陆地古气候和环境档案。从汇水区提取的近14000年的短期永久冻土岩心样本和一系列代表现代条件的地表样本将作为参考。本文将研究以下沉积物矿物学特征，这些特征被认为反映了东北西伯利亚地区的长期冰周动力学：(1)选定粒度组分中石英与长石的比例是反映霜风化程度的指标；(2)对颗粒扫描电子显微图进行图像分析，定量分析霜冻风化形成的石英颗粒形态和表面特征；(3)重矿物将作为物源指标，界定烃源岩组成和低温碎屑的变化。这些结果准备了一个基本的工具，可以通过北西伯利亚北极地区第四纪冰川循环来确定永久冻土条件的强度。这是ICDP资助的深层钻探项目未来核心研究的概念结果。

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.