Late Quaternary δ13C gradients and carbonate accumulation in the western equatorial Atlantic
Late Quaternary δ13C gradients and carbonate accumulation in the western equatorial Atlantic
复制标题
DOI：
10.1016/s0012-821x(98)00012-0
复制
发表时间：
1998-02
影响因子：
5.3
通讯作者：
S. Mulitza;C. Rühlemann;T. Bickert;W. Hale;J. Pätzold;G. Wefer
中科院分区：
文献类型：
--
作者：
S. Mulitza;C. Rühlemann;T. Bickert;W. Hale;J. Pätzold;G. Wefer
我们利用浮游和底栖有孔虫的碳同位素组成研究了赤道西部大西洋冰期-间冰期垂直 δ13C 梯度的变化。岩芯顶部测量表明，浅层的 G. sacculifer 和温跃层的 G. truncatulinoides 之间的 δ13C 差异是上部水柱垂直营养梯度的指标。在赤道西部大西洋，冰川期和间冰期寒冷亚阶段期间，G. sacculifer 和 G. truncatulinoides 之间的 δ13C 差异减小，而 G. truncatulinoides 和底栖物种 C. wuellerstorfi 之间的 δ13C 差异增大。这表明在寒冷的亚阶段，温跃层中的营养物质被耗尽，而深水中的营养物质被富集。来自西赤道大西洋的 G. truncatulinoides 和来自加勒比中间水域的 C. wuellerstorfi 的 δ13C 记录之间的协方差表明，西赤道大西洋水柱的上部主要由来自北部的营养贫乏的中部和中间水域组成。这种模式可能是亚南极地表水形成营养丰富的深层水而不是中间水的循环模式的结果。冷次阶段较低的230Th归一化碳酸盐积累率表明，地下水养分含量的降低导致了赤道西大西洋初级生产力的降低。
We investigated glacial–interglacial changes in vertical δ13C gradients in the western equatorial Atlantic using the carbon isotopic composition of planktonic and benthonic foraminifera. Core top measurements show that the δ13C difference between shallow-dwelling G. sacculifer and thermocline-dwelling G. truncatulinoides is an indicator of the vertical nutrient gradient in the upper water column. In the western equatorial Atlantic, the δ13C differences between G. sacculifer and G. truncatulinoides are reduced during glacials and cold substages of interglacials, while the δ13C differences between G. truncatulinoides and the benthonic species C. wuellerstorfi are increased. This indicates that nutrients were depleted in the thermocline and enriched in deep waters during cold substages. Covariance between the δ13C records of G. truncatulinoides from the western equatorial Atlantic and C. wuellerstorfi from Caribbean intermediate water suggests that the upper part of the western equatorial Atlantic water column was largely composed of nutrient-poor central and intermediate waters of northern origin. This pattern might have been the result of a circulation mode in which subantarctic surface waters formed nutrient-rich deep waters rather than intermediate waters. Lower230Th-normalized carbonate accumulation rates during cold substages imply that the decreased nutrient content of subsurface waters induced a lower primary productivity in the western equatorial Atlantic.