黄土高原全新世土壤碳酸盐团簇同位素的温度重建  

TEMPERATURE RECONSTRUCTION USING THE CLUMPED ISOTOPE FOR THE HOLOCENE SOIL CARBONATES ON THE CHINESE LOESS PLATEAU

作　　者：董吉宝[1] John EILER DONG Jibao;John EILER(State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi'an 710061,Shaanxi;California Institute of Technology,Pasadena,CA 91125,USA)

机构地区：[1]中国科学院地球环境研究所,黄土与第四纪地质国家重点实验室,陕西西安710061 [2]California Institute of Technology,Pasadena,CA 91125,USA

出　　处：《第四纪研究》2024年第5期1411-1420,共10页Quaternary Sciences

基　　金：中国科学院青年创新促进会项目(批准号:2021412)资助。

摘　　要：黄土高原黄土-古土壤序列中保存有丰富的土壤碳酸盐,是利用碳酸盐团簇同位素(Δ_(47))定量重建古温度的重要地质载体之一。然而,黄土高原全新世土壤碳酸盐Δ_(47)及其气候指示意义的系统研究仍然缺乏。本研究分析了黄土高原南缘渭南剖面和中部洛川剖面上部3 m沉积中保存的全新世土壤碳酸盐(钙结核)的团簇同位素组成,监测了现在地形条件下距地表4 m以内不同深度的土壤温度。结果显示,Δ_(47)定量重建的全新世土壤碳酸盐团簇同位素温度(T_(47))与现代暖季节温度相近,渭南剖面T_(47)平均值约为25℃,洛川剖面约为18℃,较区域年均温高8~10℃。根据T_(47)和土壤碳酸盐氧同位素组成(δ18O)重建的土壤水δ18O也与暖季节降水的δ18O基本一致,这些数据表明黄土高原土壤碳酸盐记录了暖季节的环境信息。值得注意的是,渭南和洛川剖面钙结核T_(47)值与其形成深度的土壤温度基本吻合,结合前人研究结果,这暗示了土壤碳酸盐形成深度对其T_(47)具有显著影响。因此,在将来土壤碳酸盐Δ_(47)的研究中,评估土壤碳酸盐形成深度至关重要。Abundant soil carbonates are preserved in the loess-paleosol sequences,which are invaluable archive for the carbonate clumped isotope(Δ_(47))analysis to quantitatively reconstruct paleotemperature and environmental changes.However,no systematic studies were conducted to investigate theΔ_(47)compositions of the Holocene soil carbonates and their climatic implications on the Chinese Loess Plateau(CLP).Thus,this study analyzed the stable and clumped isotopes of the Holocene soil carbonates obtained from the upper 3 meters in Weinan(34.5°N,109.6°E)and Luochuan(35.7°N,109.4°E)sections,which are located on the southern and middle part of the CLP,respectively.Meanwhile,the soil temperature was monitored at different depths(0.5 m,1 m,2 m and 4 m)for the upper 4 meters.The results show that the soil carbonate formation temperature(T_(47))reconstructed fromΔ_(47)values is approaching warm season temperature,and the mean T_(47)is 25℃for Weinan and 18℃for Luochuan,which are 8~10℃higher than mean annual temperature in the studied region.Furthermore,the soil water oxygen isotope compositions(δ18O)were reconstructed from T_(47)and soil carbonateδ18O,which are consistent with the monitored warm season precipitationδ18O.Altogether,these data suggest that the soil carbonates were precipitated during the warm-wet season on the CLP.Notably,the T_(47)in the two sections are similar with the measured soil temperatures at the soil carbonates formation depths.This indicates the important role of the carbonate's formation depth,because the T_(47)of soil carbonates reflected the soil temperature which is further strongly related to the soil depth.In other word,the deeper formation depth of soil carbonates will correspond to lower/mean annual temperature.This inference is supported by the recent study on the Lingtai section in central part of CLP,which show that the mean T_(47)of the soil carbonates formed in the last interglacial is 5℃lower than those for the Holocene.Besides,the published results also imply the influenc

关 键 词：土壤碳酸盐 团簇同位素(Δ_(47)) 全新世 黄土高原 季节性 

分 类 号：P534.632[天文地球—第四纪地质学] P597.2[天文地球—古生物学与地层学]