Ba/Ca ratios in Neogloboquadrina pachyderma of sedimet core 94B17

Down-core samples of the planktonic foraminifer Neogloboquadrina pachyderma sinistral from the Mendeleyev Ridge in the western Arctic Ocean have been analyzed for Ba/Ca and d18O. The apparent distribution coefficient for N. pachyderma sin. is estimated at DBa = 0.22 ± 0.02. A meltwater event is identified at around 11.8 14C kyr BP and is coincident with elevated Ba/Ca ratios. The barium enrichment is believed to be the result of enhanced weathering and erosion following glaciation. Additionally, barium may have desorbed from shelf sediments as sea level rose. Changes in Ba/Ca correlate with the retreat of the Laurentide Ice Sheet and the evolution of the Mackenzie River drainage basin. Therefore maximum Ba/Ca in Arctic surface waters at 11.8 ka may be indicative of an increase in the export of freshwater from the Arctic to the North Atlantic, potentially contributing to the onset of the Younger Dryas. This work suggests that Ba/Ca in planktonic foraminifera may be a useful indicator of the timing and processes associated with deglaciation.

对取自西北冰洋门捷列夫海岭（Mendeleyev Ridge）的左旋粗厚新球房虫（Neogloboquadrina pachyderma sinistral，浮游有孔虫（planktonic foraminifer））岩心样品，开展了钡钙比（Ba/Ca）与氧同位素δ¹⁸O分析。本次研究估算得到该左旋粗厚新球房虫的表观钡分配系数DBa为0.22±0.02。在距今约11.8个¹⁴C kyr BP处识别出一次融水事件，该事件与升高的钡钙比峰值相吻合。钡元素富集被认为是冰期结束后风化与侵蚀作用增强的结果；此外，随着海平面上升，钡元素也可从陆架沉积物中解吸析出。钡钙比的变化与劳伦冰盖（Laurentide Ice Sheet）的退缩以及马更些河流域（Mackenzie River drainage basin）的演化具有显著相关性。因此，距今11.8 ka时北冰洋表层水体中的最高钡钙比，或可指示北极向北大西洋输出的淡水通量增加，这一过程可能促成了新仙女木事件（Younger Dryas）的启动。本研究表明，浮游有孔虫壳体中的钡钙比可作为反映冰消作用相关过程与时间节点的有效地球化学指标。