Geochemistry and age model of sediment core BDP96-1

Within the framework of the Baikal Drilling Project (BDP), a 192 m long sediment core (BDP-96-1) was recovered from the Academician Ridge, a submerged topographic high between the North and Central Basins of Lake Baikal. Sedimentological, clay mineralogical and geochemical investigations were carried out on the core interval between 90 and 124 m depth, corresponding to ca. 2.4-3.4 Ma. The aim was to reconstruct the climatic and tectonic history of the continental region during the intensification of Northern Hemisphere glaciation in Late Pliocene time. A major climate change occurred in the Lake Baikal area at about 2.65 Ma. Enhanced physical weathering in the catchment, mirrored in the illite to smectite ratio, and temporarily reduced bioproduction in the lake, reflected by the diatom abundance, evidence a change towards a colder and more arid climate, probably associated with an intensification of the Siberian High. In addition, the coincident onset of distinct fluctuations in these parameters and in the Zr/Al ratio suggests the beginning of the Late Cenozoic high amplitude climate cycles at about 2.65 Ma. Fluctuations in the Zr/Al ratio are traced back to changes in the aeolian input, with high values in warmer, more humid phases due to a weaker Siberian High. Assuming that the sand content in the sediment reflects tectonic pulses, the Lake Baikal area was tectonically active during the entire investigated period, but in particular around 2.65 Ma. Tectonic movements have likely led to a gradual catchment change since about 3.15 Ma from the western towards the eastern lake surroundings, as indicated in the geochemistry and clay mineralogy of the sediments. The strong coincidence between tectonic and climatic changes in the Baikal area hints at the Himalayan uplift being one of the triggers for the Northern Hemisphere Glaciation.在贝加尔钻探项目（Baikal Drilling Project, BDP）框架下，研究人员从院士海岭——贝加尔湖北部盆地与中部盆地之间的水下地形隆起处——获取了一根长192米的沉积物岩芯（BDP-96-1）。研究人员对该岩芯90~124米深度的层段开展了沉积学、黏土矿物学与地球化学分析，该层段对应约2.4~3.4 Ma的地质时段。本研究旨在重建上新世晚期北半球冰期强化阶段，该大陆区域的气候与构造演化历史。贝加尔湖区域在约2.65 Ma时发生了一次重大气候变化：流域物理风化作用增强（可通过伊利石与蒙脱石的比值反映），同时湖泊生物生产力出现暂时性下降（可通过硅藻丰度体现），上述迹象表明区域气候向更寒冷、更干旱的方向转变，这可能与西伯利亚高压（Siberian High）的强化相关。此外，上述参数与Zr/Al比值同步出现显著波动，这表明晚新生代高振幅气候旋回于约2.65 Ma正式启动。Zr/Al比值的波动可归因于风成输入量的变化：当西伯利亚高压较弱时，气候更温暖湿润，此时Zr/Al比值较高。若假设沉积物中的砂含量可反映构造脉动，则贝加尔湖区域在整个研究时段内均处于构造活动状态，尤以约2.65 Ma时最为显著。自约3.15 Ma以来，构造运动可能导致流域逐渐从湖西周边区域转向湖东周边区域，该结论可通过沉积物的地球化学与黏土矿物学特征得到佐证。贝加尔湖区域构造与气候变化的高度耦合现象表明，喜马拉雅隆升（Himalayan uplift）是触发北半球冰期的诱因之一。