Preliminary analysis of organic biomarkers in deep-sea sediments from the Baffin Bay, North Atlantic

Abstract

To investigate the Greenland Icesheet evolution and its dynamical coupling with global climate on geological timescales, the International Ocean Discovery Program Expedition 400 has drilled a set of deep-sea sediments cores at the northeast Baffin Bay. Based on 22 sample residuals(ca. 6~10 grams each) of paleomagnetic analysis at Site U1604A and 5 bulk samples(ca. 13~16 grams each) at other sites, this study aims to conduct a pilot measurement of long-chain alkenones and n- alkanes compounds. Together with the chronological framework constrained by paleomagnetic and biostratigraphic evidence, we also test the potential of these organic biomarkers to reconstruct high-latitude seawater temperatures in the past. The results show that sea surface temperature(SST) signals extracted from U37K index, albeit with low alkenone contents (< ca. 2.5 ng/ g) of few samples, generally fluctuated from ca. 4 ℃ to 11.5 ℃, with an overall decreasing trend, during the late Pleistocene. As such, more(ca. 20 grams) bulk sediments might be sufficient to analyze long-chain alkenone unsaturation index U37K, % C37:4, and n-alkane-based proxies, which, as a result, shed valuable insight in future work on additional sampling of these Holes to further explore the link between Greenland Icesheet and oceanic conditions on long-term timescales.

为探究格陵兰冰盖的长期演化历史及其与气候系统之间的耦合联动关系，国际大洋发现计划４００航次在巴芬湾海域毗邻格陵兰冰盖西北部的陆坡／架区钻取了一系列深海沉积岩芯样品。利用航次期间完成古地磁测试后的少量样品剩余（每个约６～１０ｇ），初步测试了其中的长链烯酮和和正构烷烃组分，并结合船上获得的古地磁和生物地层学证据约束的初步年代框架，尝试分析了上述有机地球化学指标重建北大西洋高纬度海区水体温度信号的可行性。研究结果显示：尽管个别样品中长链烯酮含量偏低，但温度信号基本可靠。据此推测增加（如：约２０ｇ）全岩样品基本可以实现常规有机地球化学指标的实验室分析，为后续申请该航次岩芯的高分辨率样品以深入探究格陵兰冰盖演化与海洋关键过程积累了宝贵的经验