Formation of "Southern Component Water" in the Late Cretaceous: Evidence from Nd-isotopes
Formation of "Southern Component Water" in the Late Cretaceous: Evidence from Nd-isotopes
复制标题
晚白垩世“南方水”的形成：来自 Nd 同位素的证据
作者：
Robinson S
在过去的温室气候时期，如白垩纪，约束深海环流，是重要的了解对流传热过程，控制海洋缺氧，以及气候和构造在确定古环流模式的相对作用。晚白垩世和古近纪早期的海洋环流模型表明，在南大洋发生了显着的深水生产，但不能约束这个过程开始时，或开放的构造网关和晚白垩世气候冷却之间的时间关系。钕同位素数据从生物磷灰石（鱼的牙齿和骨头）是从较低的半深海和深海的网站在南大西洋和印度洋。在白垩纪中期，相对放射性钕同位素值表明，在这些盆地的深水循环缓慢的输入可能占主导地位的海水颗粒交换过程，并可能，容易风化的火山岩。在Campanian-Maastrichtian的Nd同位素组成的原始印度和南大西洋深水沃茨变得不那么放射性，这表明在南大洋深水形成的开始（南部组成水，SCW），与古近纪重建和海洋环流模型。南半球的冷却和坎帕尼亚期构造门户的打开可能推动了SCW的开始。
Constraining deep-ocean circulation during past greenhouse climatic periods, such as the Cretaceous, is important for understanding meridional heat transfer processes, controls on ocean anoxia, and the relative roles of climate and tectonics in determining paleocirculation patterns. Ocean circulation models for the Late Cretaceous and early Paleogene suggest that significant deep-water production occurred in the Southern Ocean, but cannot constrain when this process commenced or what the temporal relationship was between opening tectonic gateways and Late Cretaceous climatic cooling. Nd-isotope data obtained from biogenic apatite (fish teeth and bones) are presented from lower bathyal and abyssal sites in the South Atlantic and Indian Oceans. During the mid-Cretaceous, relatively radiogenic Nd-isotope values suggest that deep-water circulation in these basins was sluggish with inputs likely dominated by seawater-particle exchange processes and, possibly, easily weathered volcanic terranes. In the Campanian–Maastrichtian the Nd-isotopic composition of proto-Indian and South Atlantic deep waters became less radiogenic, suggesting the onset of deep-water formation in the Southern Ocean (Southern Component Water, SCW), consistent with Paleogene reconstructions and ocean circulation models. A combination of Southern Hemisphere cooling and the opening of tectonic gateways during the Campanian likely drove the onset of SCW.