Rock eval analysis of sediment core PS115/2_2@en

Sediment Core PS115/2-2 was recovered from the Amundsen Basin in 3600 m water depth at the eastern flank of the Gakkel Ridge during Polarstern Expedition PS115/2 in 2018 (Stein, 2019). The well-dated core is used to reconstruct in detail the interrelationship between ice-sheet dynamics and organic carbon burial in the central Eurasian Basin during the last 430 kyr, and to correlate marine and terrestrial records of the Eurasian Ice Sheet (EIS) history. Using organic-geochemical bulk parameters (i.e., TOC, C/N ratios, Rock Eval) and biomarkers, we have identified prominent well-defined sections with strongly elevated concentration of ancient (petrogenic) predominantly terrestrial OC, coinciding with glacial time intervals of extended ice sheets and the subsequent terminations/deglacials. Rock-Eval pyrolysis was performed on bulk ground sediment samples using a Rock-Eval 6 analyzer (cf., Lafarque et al., 1998) to determine (1) the amount of hydrocarbons (HC) present (S1 peak) and generated by pyrolytic degradation of the OC during heating up to 650°C (S2 peak), (2) the amount of carbon dioxide (CO2) generated from the decomposing OC during heating up to 390 °C (S3 peak), and (3) the temperature of maximum pyrolysis yield (Tmax value in °C). The HC and CO2 yields were normalized to OC and expressed as hydrogen index (HI) in mgHC/gOC and oxygen index (OI) in mgCO2/gOC, respectively, and may give information about the composition of the organic matter. Tmax values may give further information about the composition as well as the maturity of the organic matter. For details and methods, we refer to Stein et al. (this paper).沉积物岩芯PS115/2-2于2018年随‘极星号’（Polarstern）PS115/2航次采自加克尔脊（Gakkel Ridge）东侧翼的阿蒙森海盆（Amundsen Basin），水深3600米（Stein, 2019）。该定年精确的岩芯被用于精细重建过去43万年以来欧亚海盆中部冰盖动力学与有机碳埋藏之间的相互关系，并可对比欧亚冰盖（EIS）演化的海洋与陆地记录。本研究通过有机地球化学全样参数（即总有机碳（TOC）、碳氮比（C/N）、Rock Eval热解分析）及生物标志物（biomarkers），识别出多段特征清晰且显著富集古老（岩源）陆源有机碳（OC）的层位，这些层位对应冰盖大范围发育的冰期时段及随后的冰消期/气候终止期。本研究采用Rock-Eval 6型热解仪（参照Lafarque等，1998）对研磨后的全样沉积物样品开展Rock-Eval热解分析，以测定：(1) 原位烃类（HC）含量（S1峰）以及加热至650℃过程中有机碳（OC）热解降解生成的烃类含量（S2峰）；(2) 加热至390℃过程中分解态有机碳生成的二氧化碳（CO₂）含量（S3峰）；(3) 最大热解产率对应的温度（以℃计的Tmax值）。研究将烃类与二氧化碳产率归一化至有机碳含量，分别以氢指数（HI，单位为mgHC/gOC）与氧指数（OI，单位为mgCO₂/gOC）表示，二者可反映有机质的组成特征；Tmax值则可进一步揭示有机质的组成与成熟度。相关实验细节与方法可参见Stein等（本论文）。