Stable isotope record of benthic foraminifera and the planktic foraminifera Globigerinoides sacculifer from sediment core GIK13519-1, Sierra Leone Rise, eastern equatorial Atlantic

From a 10.7 m long gravity core from the Sierra Leone Rise (5°39.5' N, 19°51' W) a detailed oxygen and carbon isotope record of both planktonic and benthonic foraminifera species was obtained extending from the Recent to Jaramillo event. The analysis yielded six major results.
1. Benthos oxygen isotopes varied by 1.8-2.2 per mil from interglacial to glacial times and may indicate a synglacial cooling of North Atlantic Deep Water at 2800 m depth by 1-3°C.
2. Variable anomalies between the benthos and plankton d18O record indicate a cooling of sea-surface temperatures (SST) by up to 6 °C during some glacial stages.
3. Southerly trade winds and equatorial upwelling may excert the primary control off SST variations, in particular of extremee values of cold and warm stages and of the abrupt character of climate transitions and their leads and lags, and finally, of variable sedimentation rates.
4. The benthos d13C record correlates well with the flux and preservation of organic matter.
5. A new time scale, CARPOR, was established from the assumption that terrigenous sediment supply was ± constant bit CaCO3 varied considerably. When applied to the d18O record, three major and numerous short-term variations of sedimentation rates (0.8 to 4.0 cm/kyr) can be distinguished.
6. The climatic record was modified by bioturbation much more strongly during cold than during warm stages.

本研究采集自塞拉利昂海隆（Sierra Leone Rise，5°39.5' N, 19°51' W）一处长10.7米的重力柱样（gravity core），从中获取了覆盖全新世至哈拉米略事件（Jaramillo event）的浮游与底栖有孔虫高精度氧、碳同位素记录，共得到六项核心研究结果：
1. 底栖有孔虫的氧同位素值在间冰期至冰期区间内波动幅度达1.8~2.2‰，该结果或表明2800米水深的北大西洋深层水（North Atlantic Deep Water）在冰期阶段出现了1~3℃的同步降温。
2. 底栖与浮游有孔虫的δ¹⁸O记录之间存在可变异常，表明部分冰期阶段的海表温度（SST）最大降温幅度可达6℃。
3. 南移信风与赤道上升流可能是海表温度变化的主要调控因素，尤其体现在冷暖阶段的极端温度值、气候转型的突变特征及其相位差，以及沉积物沉积速率的波动变化。
4. 底栖有孔虫的δ¹³C记录与有机质的输入通量及保存状况具有良好的相关性。
5. 本研究基于"陆源沉积物供给基本恒定、碳酸钙（CaCO₃）含量波动显著"的假设，建立了新的年代标尺CARPOR。将该标尺应用于δ¹⁸O记录后，可区分出3次主要沉积速率变化与多次短期波动，沉积速率区间为0.8~4.0 cm/kyr。
6. 相较于暖期，冷期阶段的气候记录受生物扰动（bioturbation）的改造作用更为显著。