Late Pliocene and Early Pleistocene Variability of the REE and Nd Isotope Composition of Caribbean Bottom Water: A Record of Changes in Sea Level and Terrestrial Inputs During the Final Stages of Central American Seaway Closure
Late Pliocene and Early Pleistocene Variability of the REE and Nd Isotope Composition of Caribbean Bottom Water: A Record of Changes in Sea Level and Terrestrial Inputs During the Final Stages of Central American Seaway Closure
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DOI：
10.1029/2019pa003654
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发表时间：
2019-12
影响因子：
3.5
通讯作者：
Anne H. Osborne;E. Hathorne;P. Böning;J. Groeneveld;K. Pahnke;M. Frank
中科院分区：
文献类型：
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作者：
Anne H. Osborne;E. Hathorne;P. Böning;J. Groeneveld;K. Pahnke;M. Frank
溶解在海水中的钕的同位素组成由远端的平流成分组成，反映了水团的混合和循环，但在陆地附近也可能含有大量源自陆地来源的局部成分，例如风成或河流物质。为了使用 Nd 同位素重建古循环，检测对深海沉积物中记录的海水信号的任何局部影响非常重要。在这里，我们展示了加勒比海深处的上新世晚期和更新世早期两个经过充分研究的时间间隔的稀土元素 (REE) 和 Nd 同位素 (εNd) 记录。我们测量了弱清洁有孔虫的微量元素和稀土元素成分，以研究同一样品的 Nd 同位素信号是否包含局部成分。我们发现整个冰川时期稀土元素成分的明显变化与盆地当地陆地物质供应的增加相一致，这可能是冰川驱动的海平面变化的结果。尽管有这些较大的陆地输入，Ce 异常 (Ce/Ce*) 在冰川期变得更加明显，表明加勒比海深处通风更好。短暂的负 Nd 同位素偏移发生在四个研究的冰川期中的三个期间，独立于海洋环流变化的任何其他代理指标，表明来自当地陆源 Nd 的输入控制了信号。我们建议旨在使用 εNd 作为古循环示踪剂的研究定期测量自生相的 REE 成分，以确定任何可能的陆地对信号的影响。
The isotopic composition of neodymium dissolved in seawater consists of a distal, advected component that reflects water mass mixing and circulation but near land can also contain a large local component originating from terrestrial sources such as aeolian or fluvial material. In order to use Nd isotopes to reconstruct paleocirculation, it is important to detect any local influences on the seawater signal recorded in deep sea sediments. Here we present rare earth element (REE) and Nd isotope (εNd) records from the deep Caribbean for two well‐studied time intervals in the Late Pliocene and Early Pleistocene. We measured trace element and REE compositions of weakly cleaned foraminifera to investigate if the Nd isotope signal from the same samples contained a local component. We find distinct changes in REE compositions across glaciations that are consistent with increases in the supply of local terrestrial material to the basin likely the results of glacially driven changes in sea level. Despite these larger terrestrial inputs, the Ce anomaly (Ce/Ce*) became more pronounced during glaciations indicating a better deep Caribbean ventilation. Short negative Nd isotope excursions occurred during three of the four studied glaciations, independently of any other proxy indicators for changes in ocean circulation suggesting that inputs from local terrigenous sources of Nd controlled the signal. We recommend that studies that aim to use εNd as a paleocirculation tracer routinely measure REE compositions of the authigenic phase to identify any possible terrestrial influence on the signal.