Bulk sedimentology of the Batagay thaw slump, Northeastern Siberia

We described the Batagay permafrost sequence during the June 2014 field campaign. The 60m high outcrop was sampled from top to bottom along its height, ideally in 1m steps, but depending on its accessibility. The sampling procedure was carried out as follows: (1) the cryolithological characteristics at each sampling point were described and photographed, (2) the sampling zone was cleaned, and (3) frozen deposits were taken using a hammer and a chisel and placed into plastic bags. The wet sediments were air-dried in the field and split into subsamples for sedimentological and biogeochemical analysis in the laboratories of the Alfred Wegener Institute in Potsdam.Total carbon (TC) and total nitrogen (TN) were measured with a vario EL III element analyser and the total organic carbon (TOC) content was measured with a vario MAX analyser. Using the TOC and TN values, the TOC = TN (C = N) ratio was calculated to deduce the degree of organic matter decomposition. The lower the C/N ratio is, the higher the decomposition degree and vice versa. For TOC and stable carbon isotope (d13C) analyses, samples were decalcified for 3 h at 95 °C by adding a surplus of 1.3 N HCl. Total inorganic carbon (TIC) content was calculated by subtracting TOC from TC. Using TIC values, the carbonate content as CaCO3 was estimated via the ratios of molecular weight. The d13C of TOC values was measured with a Finnigan Delta S mass spectrometer and expressed in delta per mil notation (d, per mil) relative to the Vienna Pee Dee Belemnite (VPDB) standard with an uncertainty of 0.15 per mil. Variations in d13C values indicate changes in the local plant association and in the degree of organic matter decomposition. Lower d13C values correspond to less-decomposed organic matter, while higher d13C values reflect stronger decomposition. Mass-specific magnetic susceptibility (MS) indicative of magnetic and magnetizable minerals was measured using Bartington MS2 instruments equipped with the MS2B sensor type. The data are expressed in 10-8 m3 kg-1 (SI).

本研究针对2014年6月野外考察期间获取的巴塔盖（Batagay）多年冻土序列开展了系统描述。该露头高60米，沿其垂直高度自上而下进行采样，理想采样间距为1米，实际采样间距则视露头可及性灵活调整。采样流程具体如下：(1) 对每个采样点的冻土岩石学（cryolithological）特征进行描述并拍照记录；(2) 清理采样区域的表面杂物；(3) 使用铁锤与凿子采集冻土沉积物，并将其装入聚乙烯密封袋中。湿态沉积物先在野外自然风干，随后分装为子样本，送往位于波茨坦的阿尔弗雷德·魏格纳研究所（Alfred Wegener Institute）实验室，开展沉积学与生物地球化学相关分析。总碳（Total Carbon, TC）与总氮（Total Nitrogen, TN）含量采用vario EL III型元素分析仪测定，总有机碳（Total Organic Carbon, TOC）含量则采用vario MAX型分析仪测定。基于TOC与TN的测定值，计算得到C/N比值，以此推演有机质的分解程度：C/N比值越低，有机质分解程度越高，反之亦然。针对TOC与稳定碳同位素（stable carbon isotope, δ¹³C）的分析，需将样本置于95℃环境下，加入过量1.3当量浓度盐酸（HCl）脱钙3小时。总无机碳（Total Inorganic Carbon, TIC）含量通过总碳（TC）减去总有机碳（TOC）计算得到；基于TIC的测定值，通过分子量比值估算以碳酸钙（CaCO₃）计的碳酸盐含量。总有机碳的δ¹³C值采用Finnigan Delta S型质谱仪测定，以相对于维也纳佩德迪箭石（Vienna Pee Dee Belemnite, VPDB）标准的δ千分比（‰）形式表示，测定不确定度为0.15‰。δ¹³C值的变化可反映当地植物群落组成与有机质分解程度的改变：δ¹³C值越低，对应有机质分解程度越弱；反之，δ¹³C值越高则代表有机质分解程度越强。表征磁性与可磁化矿物的质量磁化率（Mass-specific magnetic susceptibility, MS）采用搭载MS2B型传感器的Bartington MS2型仪器测定，数据以国际单位制（SI）下的10⁻⁸ m³·kg⁻¹形式表示。