Occurrence of thick Ethmodiscus oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical South Atlantic
Occurrence of thick Ethmodiscus oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical South Atlantic
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DOI：
10.1016/j.palaeo.2005.10.026
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发表时间：
2006-06
期刊：
影响因子：
--
通讯作者：
O. Romero;F. Schmieder
中科院分区：
文献类型：
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作者：
O. Romero;F. Schmieder
在一般的钙质沉积序列中，在中大西洋海脊两侧23°-33°S之间的5个亚热带南大西洋柱样中发现了厚度不等的巨型硅藻ethmodisus层。有两种类型的渗出物：(几乎)单一种类的水生生物层和以水生生物为主的水生生物层，伴随着几种热带/亚热带、营养稀少的水生硅藻。两个最厚的民族盘层出现在约29°S附近的GeoB3801-6中，并分别在MIS14和MIS12晚期堆积。气旋阀的下部浓度范围为3.4⁎10 4~2.3⁎10 7阀门g−1。我们从锋面系统迁移和温盐环流变化的背景下讨论了软泥的形成。在今天的中上层、低营养水域底层沉积物中出现的国家海洋渗出物与大约530ka的中更新世过渡的末期事件有关，当时海洋环流在一段时间的NADW产量减少后重新安排。
Within generally calcareous sediment sequences, layers of variable thickness of the giant diatom Ethmodiscus were found in five cores recovered in the Subtropical South Atlantic between 23° and 33°S from both sides of the Mid-Atlantic Ridge. Two types of oozes occur: (almost) monospecific layers of Ethmodiscus and layers dominated by Ethmodiscus, with several accompanying tropical/subtropical, oligotrophic-water diatoms. The two thickest Ethmodiscus layers occur in GeoB3801-6 around 29°S, and accumulated during late MIS 14 and MIS 12, respectively. Downcore concentrations of Ethmodiscus valves range between 3.4⁎104and 2.3⁎107valves g−1. We discuss the ooze formation in the context of migration of frontal systems and changes in the thermohaline circulation. The occurrence of Ethmodiscus oozes in sediments underlying the present-day pelagic, low-nutrient waters is associated with a terminal event of the Mid-Pleistocene Transition at around 530 ka, when the ocean circulation rearranged after a period of reduced NADW production.