Tectonically restricted deep-ocean circulation at the end of the Cretaceous greenhouse
Tectonically restricted deep-ocean circulation at the end of the Cretaceous greenhouse
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DOI：
10.1016/j.epsl.2013.03.019
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发表时间：
2013-04
影响因子：
5.3
通讯作者：
S. Voigt;C. Jung;O. Friedrich;M. Frank;C. Teschner;J. Hoffmann
中科院分区：
文献类型：
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作者：
S. Voigt;C. Jung;O. Friedrich;M. Frank;C. Teschner;J. Hoffmann
全球海洋环流向南部高纬度深水生产的演变被认为与白垩纪中期极端温暖的气候向较凉爽的新生代气候过渡密切相关。然而，气候变冷和大洋航道的开闭对深海环流模式的相对影响仍未得到解决。本文根据南大西洋、南大洋和原印度洋不同水深的高分辨率放射性成因钕(ND)同位素数据，重建了白垩纪末期的中-深水环流。我们的数据记录了南大西洋和南大洋存在明显不同的中间水的ND同位素组成。特别是，具有高放射性成因的ND同位素特征的水团很可能来自与热点有关的强烈火山活动，该水团沐浴在71至69 Ma之间的沃尔维斯山脊，形成了一道屏障，阻止了南大洋和北大西洋盆地之间的深水交换。我们认为，新生代的全球深海环流模式在白垩纪末期仍然受到构造屏障的抑制，6800万年前，大量的、主要是区域形成的、来源于中至深水的深海提供了深海。
The evolution of global ocean circulation toward deep-water production in the high southern latitudes is thought to have been closely linked to the transition from extreme mid-Cretaceous warmth to the cooler Cenozoic climate. The relative influences of climate cooling and the opening and closure of oceanic gateways on the mode of deep-ocean circulation are, however, still unresolved. Here we reconstruct intermediate- to deep-water circulation for the latest Cretaceous based on new high-resolution radiogenic neodymium (Nd) isotope data from several sites and for different water depths in the South Atlantic, Southern Ocean, and proto-Indian Ocean. Our data document the presence of markedly different intermediate water Nd-isotopic compositions in the South Atlantic and Southern Ocean. In particular, a water mass with a highly radiogenic Nd isotope signature most likely originating from intense hotspot-related volcanic activity bathed the crest of Walvis Ridge between 71 and 69Ma, which formed a barrier that prevented deep-water exchange between the Southern Ocean and the North Atlantic basins. We suggest that the Cenozoic mode of global deep-ocean circulation was still suppressed by tectonic barriers in the latest Cretaceous, and that numerous, mostly regionally-formed and sourced intermediate to deep waters supplied the deep ocean prior to 68millionyr ago.