Late Quaternary climate change from δ18O records of multiple species of planktonic foraminifera: High‐resolution records from the Anoxic Cariaco Basin, Venezuela
Late Quaternary climate change from δ18O records of multiple species of planktonic foraminifera: High‐resolution records from the Anoxic Cariaco Basin, Venezuela
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多种浮游有孔虫物种 δ18O 记录的晚第四纪气候变化：委内瑞拉缺氧卡里亚科盆地的高分辨率记录
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
D. Murray
中科院分区：
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作者：
Hui‐Ling Lin;L. Peterson;J. Overpeck;S. Trumbore;D. Murray
加勒比海南缘的季节性信风引起的上升流是由于热带辐合带的年度迁移而发生的。卡里亚科盆地（委内瑞拉大陆架上的一个小型缺氧盆地）的层状高沉积率沉积物清楚地记录了过去上升流强度的巨大变化。由于卡里亚科盆地的沉积物基本上未受生物扰动，因此它们提供了一个天然的机会来研究多种浮游有孔虫类群的稳定同位素记录，并评估它们对现代水文学以及上升流强度和气候的时间变化的敏感性。提供了过去 28 kyr 期间四个主要有孔虫类群的氧同位素数据 (δ18O)。来自 Globigerina bulloides 的 δ18O 数据经过非平衡降水校正后，可用作冬春季上升流季节海面状况的监测。白色 Globigerinoides ruber 的 δ18O 数据被用作近地表年平均状况的测量，而粉红色 G. ruber 数据与作为夏秋季非上升流季节端元状况的指标一致。来自较深居所的 Neogloboquadrina dutertrei 的数据提供了有关当地温跃层底部附近条件的信息。在末次冰期期间，来自 G. ruber 的 δ18O 数据和普遍减少的种间差异表明卡里亚科盆地的地表水冷却高达 4°C。这种长期变冷似乎与沿海上升流强度的变化无关，但可能反映了更大的加勒比海区域的变冷。叠加在这一模式上的是 12.6 至 ∼10 ka 之间的 G. bulloides 和 N. dutertrei 之间的 δ18O 数据的收敛，这意味着末次冰消期期间出现了更强的上升流。这种情况与目前高生产率的其他证据是一致的。大约 14ka 时，在所有类群中观察到的 δ18O 急剧消耗事件似乎是由于向加勒比南部排放的淡水增加而产生的，这表明区域降雨量增加或安第斯山脉冰川融化的影响。粉红色 G. ruber 的最低 δ18O 值在 6-7 ka 左右记录了全新世中期夏季海面温度升高和/或盐度降低。
Seasonal trade wind-induced upwelling along the southern margin of the Caribbean Sea occurs in response to the annual migration of the Intertropical Convergence Zone. Laminated, high deposition rate sediments of the Cariaco Basin, a small anoxic basin on the Venezuelan continental shelf, clearly record large changes in the past intensity of this upwelling. Because sediments of the Cariaco Basin are largely unbioturbated, they offer a natural opportunity to study the stable isotopic records of multiple planktonic foraminiferal taxa and to evaluate their sensitivity to both the modern hydrography and temporal changes in upwelling intensity and climate. Oxygen isotope data (δ18O) from four dominant foraminiferal taxa are presented for the time period covering the last 28 kyr. The δ18O data from Globigerina bulloides, after correction for nonequilibrium precipitation, are used as a monitor of sea surface conditions during the winter-spring upwelling season. The δ18O data from white Globigerinoides ruber are used as a measure of annual-average conditions in the near surface, while pink G. ruber data are consistent with use as an index of endmember conditions during the summer-fall nonupwelling season. Data from the deeper dwelling Neogloboquadrina dutertrei yield information on conditions near the base of the local thermocline. During the last glacial, δ18O data from G. ruber and generally reduced interspecific differences indicate cooling of surface waters over the Cariaco Basin by up to 4°C. This longer-term cooling does not appear to be related to changes in upwelling intensity along the coast but may instead reflect more regional cooling of the larger Caribbean. Superimposed on this pattern, between 12.6 and ∼10 ka, is a convergence of δ18O data between G. bulloides and N. dutertrei, implying much stronger upwelling during the last deglaciation. This scenario is consistent with other evidence for high productivity at this time. At ∼14 ka, a sharp δ18O depletion event observed in all taxa seems to have been produced by increased freshwater discharge to the southern Caribbean, suggesting either higher regional rainfall or the influence of glacial melting in the Andes. Minimum δ18O values of pink G. ruber around 6–7 ka record warmer summer sea surface temperatures and/or decreased salinity in the mid-Holocene.