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新生代地球表面从两极无冰的温室地球变为现今两极终年有冰的冰室地球, 最重大的降温事件是发生在距今约33.7 Ma始新世/渐新世界线附近的渐新世初大冰期事件(EOGM). 南大西洋深水大洋钻探计划(ODP)第208航次1262站和1265站35~30 Ma期间的浮游和底栖有孔虫氧碳同位素、碳酸钙和粗组分含量, 结合颜色反射率和磁化率的高分辨率记录, 揭示出表层和深水都发生了这一全球降温事件. 分析表明, 氧同位素在渐新世初33.5~33.1 Ma记录的EOGM事件代表了南极东部冰盖的规模, 表示当时世界海水的表层和深部水温大幅度降低. 碳同位素d 13C在EOGM事件期间发生很大的正偏移, 说明全球碳储库发生重要转型, 可能反映有机碳埋藏速率突然增加或生产力的分布发生时空变化. 同时, 岩性组成、碳酸钙含量、颜色反射率和粗组分在始新世/渐新世界线附近都发生了重要变化, 反映当时碳酸盐补偿深度(CCD)突然快速变深. 由颜色反射率揭示出的碳酸钙含量变化具有100和400 ka的地球轨道偏心率长周期, 进一步显示早渐新世全球气候变化的轨道驱动机制.
The Cenozoic Earth’s surface has changed from a polar ice-free greenhouse to an ice-filled icehouse now bipolar. The most significant cooling event occurred at the beginning of the Oligocene / Oligocene line near the Eocene / Oligocene line about 33.7 Ma (EOGM). The planktonic and benthic foraminiferal oxygen and carbon isotopes, calcium carbonate and coarse component contents during the period from 1260 to 1265 and the 35 to 30 Ma from station 1265 at the South Atlantic Ocean Deepwater Ocean Drilling Program (ODP) High-resolution color reflectance and magnetic susceptibility data reveal that both global and deep-water events have occurred, and the EOGM events recorded during the Oligocene 33.5-33.1 Ma indicate that the oxygen isotopes represent the eastern Antarctic ice sheet Indicating a significant reduction in the surface and deep water temperatures of the world’s oceans at that time.The carbon isotope d 13C experienced a large positive shift during the EOGM event indicating a major transformation of the global carbon reservoir that may reflect a sudden increase in the burial rate of organic carbon or Productivity distribution changes spatially and spatially.At the same time, lithologic composition, calcium carbonate content, color reflectance and coarse fraction have undergone significant changes in the vicinity of Eocene / Oligocene line, reflecting that at that time Salt compensation depth (CCD) suddenly becomes deep quickly. Calcium carbonate reveal changes color by having a reflectance of 100 and 400 ka earth orbit eccentricity long period, a further display early orbital drive mechanism becoming the new world of global climate change.