Climatically driven changes in sediment supply on the SW Iberian shelf since the Last Glacial Maximum
Climatically driven changes in sediment supply on the SW Iberian shelf since the Last Glacial Maximum
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DOI：
10.1016/j.epsl.2011.10.002
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发表时间：
2011-12
影响因子：
5.3
通讯作者：
R. Stumpf;M. Frank;J. Schönfeld;B. Haley
中科院分区：
文献类型：
--
作者：
R. Stumpf;M. Frank;J. Schönfeld;B. Haley
伊比利亚西南陆架的海洋沉积物组合受到不同来源的影响，这些来源随着末次盛冰期以来的环境变化而变化。快速的、年代际尺度的地中海翻转环流允许来自整个地中海的悬浮粒子混合。它们被地中海流出水（MOW）携带的悬浮颗粒物（SPM）所携带，通过直布罗陀海峡进入北大西洋东部，并在加的斯湾的中等深度和沿着葡萄牙大陆边缘扩散。北非沙尘和来自伊比利亚半岛的河流输送颗粒是影响西南伊比利亚大陆架MOW流道SPM特征和收支平衡的其他主要泥沙来源。重建过去约23000calyrb.p.以来气候和环流驱动的沉积物供应变化。在加的斯湾（577m水深）的一个重力岩心和葡萄牙陆架（1745m， 1974m水深）的两个重力岩心中获得了粘土级沉积物组分的放射性成因Nd、Sr和Pb同位素记录。这些记录由同一组样品中粘土矿物丰度的时间序列分析补充。与预期相反，从LGM到全新世的过渡并没有伴随着沉积物物源或运输的强烈变化，而海因里希事件1 （H1）和非洲湿润期（AHP）的同位素特征显著不同，反映了H1期间来自北美克拉通的冰筏物质的供应和AHP期间撒哈拉沙尘供应的减少引起的来源贡献的变化。数据还表明，粘土矿物丰度变化的时间与放射性成因同位素特征的时间解耦。
The assemblages of marine sediments on the SW Iberian shelf have been controlled by contributions from distinct sources, which have varied in response to environmental changes since the Last Glacial Maximum (LGM). The rapid, decadal scale Mediterranean overturning circulation permits mixing of suspended particles from the entire Mediterranean Sea. They are entrained into the suspended particulate matter (SPM) carried by Mediterranean Outflow Water (MOW), which enters the eastern North Atlantic through the Strait of Gibraltar and spreads at intermediate depths in the Gulf of Cadiz and along the Portuguese continental margin. Other major sediment sources that have contributed to the characteristics and budget of SPM along the flow path of MOW on the SW Iberian shelf are North African dust and river-transported particles from the Iberian Peninsula. To reconstruct climate- and circulation-driven changes in the supply of sediments over the past ~23000calyrB.P., radiogenic Nd, Sr and Pb isotope records of the clay-size sediment fraction were obtained from one gravity core in the Gulf of Cadiz (577m water depth) and from two gravity cores on the Portuguese shelf (1745m, 1974m water depth). These records are supplemented by time series analyses of clay mineral abundances from the same set of samples. Contrary to expectations, the transition from the LGM to the Holocene was not accompanied by strong changes in sediment provenance or transport, whereas Heinrich Event 1 (H1) and the African Humid Period (AHP) were marked by significantly different isotopic signatures reflecting changes in source contributions caused by supply of ice rafted material originating from the North American craton during H1 and diminished supply of Saharan dust during the AHP. The data also reveal that the timing of variations in the clay mineral abundances was decoupled from that of the radiogenic isotope signatures.