Geochemistry of IODP Site 306-U1314

Integrated Ocean Drilling Program (IODP) Site U1314 of the North Atlantic is a critical sedimentary archive record of subpolar deep water from the southern Gardar Drift for which we derived an age model of orbital resolution for the last 1.8 Ma. This chronology combined with high-resolution (cm scale) X-ray fluorescence core scanning measurements of major elements allows tracking changes in terrigenous provenance during the last 1.1 Ma. Low Potassium to Titanium (K/Ti) ratios reflect enhanced transport of basalt-derived titanomagnetites during warm climate intervals, while high K/Ti ratios indicate a dominance of acidic sediment sources typical for glacial and stadial events. Changes in K/Ti and magnetic concentration at Site 1314 are coeval with fluctuations in smectite content and grain size data from nearby piston cores, suggesting that the provenance changes are mainly controlled by variable flow of the Iceland-Scotland Overflow Water, an important branch of North Atlantic Deep Water. Furthermore, K/Ti variations on orbital time scales show a striking similarity to the deep sea d13C record from ODP Site 607. Pervasive features of the K/Ti time series during and after the Mid-Pleistocene Transition are suborbital changes similar to Dansgaard/Oeschger and Bond oscillations that appear to be strongly amplified during ice growth phases when global benthic d18O was within the range of 4.1–4.6 per mil. The strong increase in variability of sediment provenance and subsequently deep hydrography at benthic d18O values below ~4.1 suggests that the extent of glaciations and, therefore, sea level corresponding to this value constitutes an important physical threshold that was persistent at least for the last 1.1 Ma.

北大西洋综合大洋钻探计划（Integrated Ocean Drilling Program, IODP）U1314站位是加达尔漂移南部亚极地深层水的关键沉积记录载体，本数据集针对该站位构建了过去180万年的轨道分辨率年代模型。结合高分辨率（厘米级）常量元素X射线荧光岩心扫描测量数据，该年代序列可用于追溯过去110万年以来的陆源物源变化。低钾钛比（K/Ti）反映暖期气候阶段玄武岩成因钛磁铁矿的搬运作用增强，而偏高的K/Ti比值则指示冰期与冰阶事件中典型的酸性沉积物源占主导。U1314站位的K/Ti比值与磁浓度变化，与附近活塞岩心的蒙脱石含量及粒度数据波动具有同期性，表明物源变化主要受控于冰岛-苏格兰溢流深水——北大西洋深层水的重要分支——的流量变化。进一步研究发现，轨道时间尺度下的K/Ti比值变化与大洋钻探计划（Ocean Drilling Program, ODP）607站位的深海碳同位素（δ¹³C）记录具有显著相似性。中更新世转型期及之后的K/Ti时间序列普遍存在亚轨道尺度变化，其特征与丹斯果-奥什格振荡及邦德振荡一致，这类振荡在全球底栖氧同位素（δ¹⁸O）处于4.1‰~4.6‰范围的冰生长阶段被显著放大。当底栖δ¹⁸O值低于约4.1‰时，沉积物物源及后续深层水文学的变异性显著增强，这表明冰期规模以及对应此数值的海平面高度构成了一个重要的物理阈值，该阈值至少在过去110万年中持续存在。