North Atlantic Deep Water formed by the later middle Miocene
North Atlantic Deep Water formed by the later middle Miocene
复制标题
中新世晚期形成的北大西洋深水
作者：
P. Blanc;D. Rabussier;C. Vergnaud;J. Duplessy
有证据表明，在中生代和古近纪时期，南北亚极地地区都是温和的气候1,2。与现今温暖的赤道地区和冰雪覆盖的极地地区的气候对称不同，中新世中期形成了强烈的行星不对称，当时南极冰盖形成，而北部高纬度地区仍未被冰川覆盖。当大约3万年前上新世中期北半球大陆冰盖形成时，这种对称性得到了恢复。这些变化影响了海洋中深水的形成。目前，寒冷稠密的海底水只起源于两个高纬度地区——威德尔海产生南极底水，挪威海产生挪威海溢出水，挪威海溢出水混合后成为北大西洋深水的主要组成部分。南大洋冷深水的形成始于始新世-渐新世界线3。我们在此提出了来自DSDP站点116的底栖有孔虫的同位素分析的新证据，表明北大西洋含氧深水的产生始于中新世晚期，~ 12 Myr以前。
There is evidence that in Mesozoic and Palaeogene times both north and south subpolar areas had a mild climate1,2. Unlike the present day climatic symmetry, with warm equatorial regions and ice-covered polar regions, a strong planetary asymmetry developed in the middle Miocene, when the Antarctic ice cap was established while the northern high latitudes remained unglaciated3. The symmetry was restored when a Northern Hemisphere continental ice cover was established ∼3 Myr ago in the middle Pliocene4. These changes influenced the formation of deep water in the ocean. At present the cold, dense bottom waters originate in only two high latitude areas—the Weddell Sea producing Antarctic Bottom Water, and the Norwegian Sea, producing Norwegian Sea Overflow Water which after mixing is a major component of the North Atlantic Deep Water. The production of cold deep water in the Southern Ocean started at the Eocene–Oligocene boundary3. We present here new evidence from isotope analyses of benthic Foraminifera from DSDP site 116 indicating that the production of oxygenated deep water in the North Atlantic Ocean started in the late middle-Miocene, ∼12 Myr ago.