Recurrent decadal-scale dust events over Holocene western Africa and their control on canyon turbidite activity (Mauritania)
Recurrent decadal-scale dust events over Holocene western Africa and their control on canyon turbidite activity (Mauritania)
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DOI：
10.1016/j.quascirev.2008.09.024
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发表时间：
2009-02
影响因子：
4
通讯作者：
T. Hanebuth;R. Henrich
中科院分区：
文献类型：
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作者：
T. Hanebuth;R. Henrich
来自大陆架和斜坡的沉积物记录可能以最高的时间分辨率提供古环境信息，但由于强烈的侵蚀和改造过程，往往受到阻碍。在这里，我们展示了毛里塔尼亚北部一个特殊的陆架泥质带沉积中心的全新世沉积记录，与位于邻近大陆斜坡的大峡谷系统内的第二个沉积核心进行了比较。这两个记录都具有卓越的连续性和最高的时间分辨率(9a/cm)，并通过沉积学和地球化学方法进行了研究。陆架档案中保存着一系列清晰的、反复出现的尘埃峰。每一次事件都只持续了十年，似乎与峡谷中的一个单独的浊积层重合。因此，一个联合机制应该对这两个矿床负责，我们建议一个区域大气触发机制。只有短暂的信风增强才会导致撒哈拉西部非洲地区出现如此明显的干旱。其影响将是大量的粉尘输出到陆架和斜坡。最近从西非开发的高分辨率干旱和湿度记录支持在全新世存在这些事件，并确认它们受大西洋系统控制，最南达19°N。
Sediment records from continental shelves and slopes might provide paleoenvironmental information in the highest temporal resolution but are often hampered due to strong erosional and reworking processes. Here, we present a Holocene sedimentary record from an exceptional shelf mud belt depocenter off northern Mauritania, compared to a second sediment core located inside a large canyon system at the adjacent continental slope. Both records are of outstandingly continuous and highest temporal resolution (9a/cm) and are investigated by sedimentological and geochemical methods. A series of sharply defined, recurrent dust peaks is preserved in the shelf archive. Each event has lasted for a single decade only and seems to coincide with an individual turbidite bed in the canyon. A joint mechanism should, thus, be responsible for both of these deposits and we suggest a regional atmospheric trigger. Only short-lasting Trade wind strengthening would cause such pronounced aridity over western Saharan Africa. The effect would be massive dust export to shelf and slope. Recently developed high resolution aridity and humidity records from western Africa support the existence of these events over the Holocene and identify them as being controlled by the Atlantic system as far south as 19°N.