Evaluating controls on planktonic foraminiferal geochemistry in the Eastern Tropical North Pacific
Evaluating controls on planktonic foraminiferal geochemistry in the Eastern Tropical North Pacific
复制标题
评估对热带北太平洋东部浮游有孔虫地球化学的控制
DOI：
10.1016/j.epsl.2016.07.039
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发表时间：
2016
影响因子：
5.3
通讯作者：
E. Tappa
中科院分区：
文献类型：
--
作者：
K. Gibson;R. Thunell;M. Machain;J. Fehrenbacher;H. Spero;K. Wejnert;X. Nava;E. Tappa
为了探索热带北太平洋东部的水柱水文和有孔虫地球化学之间的关系，我们提供了2006-2012年从特万特佩克湾维护的沉积物捕集器系泊中收集的三种浮游有孔虫（Globigerinoides ruber，Globigerina bulloides和Globorotalia menardii）的δ O 18和Mg/Ca记录。混合层物种G. ruber和G. bulloides和温跃层居民G. menardii跟踪上升流的季节变化。记录表明，在厄尔尼诺现象的高峰期上升流增加，在六年期间分层总体减少。对于所有这三个物种，镁/钙比高于已在以前的研究中报道的，并显示出不良的相关性钙化温度。我们认为，混合层中的低pH值（7.6-8.0）和[CO 3 2-]值（1070 -120 μmol/kg）有助于该区域较高Mg/Ca比的总体趋势。激光烧蚀电感耦合质谱分析G。具有高Mg/Ca比（> 9 mmol/mol）的球状体揭示了无机方解石的次级涂层的存在，其Mg/Ca和Mn/Ca比高达比原生方解石中的这些元素比高的数量级，沿着具有升高的Sr/Ca和Ba/Ca比。在高初级生产力时期发现了一些具有异常高Mg/Ca的样品，这表明蚀变可能与水体中贫氧沃茨中有机质的矿化导致碳酸盐饱和度的变化有关。虽然在有孔虫化石上也观察到了类似的贝壳分层，但这是第一次在从水柱中收集的贝壳中研究这种蚀变。我们的研究结果表明，海水碳酸盐化学作用在海底沉积之前影响有孔虫方解石微量元素：钙比，特别是在高产、低氧环境中。
To explore relationships between water column hydrography and foraminiferal geochemistry in the Eastern Tropical North Pacific, we present δ O 18 and Mg/Ca records from three species of planktonic foraminifera, Globigerinoides ruber, Globigerina bulloides, and Globorotalia menardii, collected from a sediment trap mooring maintained in the Gulf of Tehuantepec from 2006–2012. Differences in δ O 18 between mixed-layer species G. ruber and G. bulloides and thermocline-dweller G. menardii track seasonal changes in upwelling. The records suggest an increase in upwelling during the peak positive phase of El Niño, and an overall reduction in stratification over the six-year period. For all three species, Mg/Ca ratios are higher than what has been reported in previous studies, and show poor correlations to calcification temperature. We suggest that low pH (7.6–8.0) and [CO 3 2−] values (∼ 70–120 μmol/kg) in the mixed layer contribute to an overall trend of higher Mg/Ca ratios in this region. Laser Ablation Inductively Coupled Mass Spectrometry analyses of G. bulloides with high Mg/Ca ratios (> 9 mmol/mol) reveal the presence of a secondary coating of inorganic calcite that has Mg/Ca and Mn/Ca ratios up to an order of magnitude higher than these elemental ratios in the primary calcite, along with elevated Sr/Ca and Ba/Ca ratios. Some of the samples with abnormally high Mg/Ca are found during periods of high primary productivity, suggesting the alteration may be related to changes in carbonate saturation resulting from remineralization of organic matter in oxygen-poor waters in the water column. Although similar shell layering has been observed on fossil foraminifera, this is the first time such alteration has been studied in shells collected from the water column. Our results suggest a role for seawater carbonate chemistry in influencing foraminiferal calcite trace element: calcium ratios prior to deposition on the seafloor, particularly in high-productivity, low-oxygen environments.
影响因子：
3.9
作者：
Fehrenbacher, Jennifer S.;Spero, Howard J.;Eggins, Stephen
通讯作者：
Eggins, Stephen