Chronology and annual proxy data of Lago Grande di Monticchio sediments

We present new annual sedimentological proxies and sub-annual element scanner data from the Lago Grande di Monticchio (MON) sediment record for the sequence 76-112 thousand years before present (ka). They are combined with the previously published decadal to centennial resolved pollen assemblage in order to provide a comprehensive reconstruction of six major abrupt stadial spells (MON 1-6) in the central Mediterranean during early phase of the last glaciation. These climatic oscillations are defined by intervals of thicker varves and high Ti-counts and coincide with episodes of forest depletion interpreted as Mediterranean stadial conditions (cold winter/dry summer). Our chronology, labelled as MON-2014, has been updated for the study interval by tephrochronology and repeated and more precise varve counts and is independent from ice-core and speleothem chronologies. The high-resolution Monticchio data then have been compared in detail with the Greenland ice-core d18O record (NorthGRIP) and the northern Alps speleothem d18Ocalcite data (NALPS). Based on visual inspection of major changes in the proxy data, MON 2-6 are suggested to correlate with Greenland stadials (GS) 25-20. MON 1 (Woillard event), the first and shortest cooling spell in the Mediterranean after a long phase of stable interglacial conditions, has no counterpart in the Greenland ice core, but coincides with the lowest isotope values at the end of the gradual decrease in d18Oice in NorthGRIP during the second half of the Greenland interstadial (GI) 25. MON 3 is the least pronounced cold spell and shows gradual transitions, whereas its NorthGRIP counterpart GS 24 is characterized by sharp changes in the isotope records. MON 2 and MON 4 are the longest most and pronounced oscillations in the MON sediments in good agreement with their counterparts identified in the ice and spelethem records. The length of MON 4 (correlating with GS 22) supports the duration of stadial proposed by the NALPS timescales and suggests ca 500 yr longer duration than calculated by the ice-core chronologies GICC05modelext and AICC2012. Absolute dating of the cold spells provided by the MON-2014 chronology shows good agreement among the MON-2014, the GICC05modelext and the NALPS timescales for the period between 112 and 100 ka. In contrast, the MON-2014 varve chronology dates the oscillations MON 4 to MON 6 (92-76 ka) ca. 3,500 years older than the most likely corresponding stadials GS 22 to GS 20 by the other chronologies.

本研究针对蒙蒂乔尼奥大湖（Lago Grande di Monticchio, MON）76~112千年之前（ka）的沉积序列，发布全新的年度尺度沉积学代用指标数据集与亚年度元素扫描数据。本研究将上述数据与已发表的十年至百年分辨率孢粉组合数据相结合，全面重建了末次冰期早期地中海中部地区的6次重大突发性冰阶事件（MON 1~6）。这些气候振荡以纹泥（varve）厚度增加与钛元素计数升高为识别标志，同时对应森林退化事件，即地中海冰阶环境（冬季寒冷、夏季干旱）。本研究的年代标尺命名为MON-2014，通过火山灰年代学、重复高精度纹泥计数对研究区间进行了更新，且独立于冰芯与石笋年代标尺。随后，本研究将高分辨率的蒙蒂乔尼奥湖沉积数据与格陵兰冰芯氧同位素18（d¹⁸O）记录（北格陵兰冰芯项目，NorthGRIP）以及北阿尔卑斯石笋方解石氧同位素（d¹⁸Ocalcite）数据（NALPS）进行了详细对比。基于代用指标数据的主要变化目视识别结果，MON 2~6被认为与格陵兰冰阶（Greenland Stadials, GS）25~20具有对应关系。MON 1（沃亚尔事件，Woillard event）是长期稳定间冰期环境结束后地中海地区首次也是历时最短的冷期事件，未在格陵兰冰芯中找到对应信号，但与格陵兰间冰阶（Greenland Interstadial, GI）25后半段北格陵兰冰芯中冰芯氧同位素（d¹⁸Oice）逐渐降低末期的最低同位素值相吻合。MON 3是本次识别的6次冷期中强度最弱的事件，其变化过程较为平缓，而对应的北格陵兰冰芯记录GS 24则以同位素记录的剧烈波动为特征。MON 2与MON 4是MON沉积序列中历时最长、强度最显著的气候振荡事件，与冰芯及石笋记录中识别出的对应事件吻合度极高。与GS 22对应的MON 4事件的持续时长，支持了NALPS年代标尺提出的冰阶持续时间，且比冰芯年代标尺GICC05modelext与AICC2012的计算结果长约500年。基于MON-2014年代标尺得到的冷期绝对定年结果显示，在112~100 ka时段内，MON-2014、GICC05modelext与NALPS三种年代标尺的定年结果一致性良好。与之相反，MON-2014纹泥年代标尺将MON 4~6事件（92~76 ka）的定年结果，比其他年代标尺对应的格陵兰冰阶GS 22~GS 20的最可能定年结果老约3500年。