The Biogeochemical Aftermath of Neoproterozoic Ice Ages

新元古代冰河时代的生物地球化学后果

• 批准号: 0126378
• 负责人: Alan Kaufman
• 金额: $ 16.4万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-15 至 2004-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0126378&HistoricalAwards=false
• 关键词: Biogeochemical; Aftermath; Neoproterozoic; Ice; Ages

ABSTRACTThe Biogeochemical Aftermath of Neoproterozoic Ice AgesThe proposed research aims to critically test the celebrated Snowball Earth hypothesis, which predicts that several times in the Neoproterozoic (543-1000 million years ago), the entire planet was blanketed from the poles to equator with continental glaciers and sea ice. To overcome such extreme conditions it has been suggested that over millions of years atmospheric carbon dioxide concentration must have risen to over 100 times its present inventory, eventually building up enough greenhouse gas to warm the frozen planet. On one hand, the materials required for the enigmatic carbonates (which cap these Neoproterozoic glacial sediments worldwide) may have come from the intense weathering of the continents under such a CO2-charged atmosphere. Alternatively, the source of these materials may have derived from the deep ocean where sulfate-reducing bacteria dominated the water column - similar to the present-day anoxic Black Sea - during widespread, yet less severe and shorter glacial epochs. Testing the validity of either of these end-member hypotheses will require detailed study of the elemental, mineralogical, textural, and stable isotopic compositions of the cap carbonates. Samples from the Otavi Group in Namibia (where the critical evidence for global glaciation was first amassed), and in demonstrably equivalent strata from the Bambui and Macaubas groups of Brazil will be analyzed. Regional mapping and high-resolution stratigraphic studies of the thick, carbonate-dominated Brazilian successions will aid in the evaluation of models that seek to explain these severe oscillations of Precambrian climate.

摘要Neoperorogoic Ice Agesthe的生物地球化学后果提出的研究旨在批判性地测试著名的雪球地球假说，该假设预测，在Neoroperozoic（543-1亿年前）（543-1亿年前）（543-1亿年前），整个星球都覆盖了与大陆冰川和海上冰冰的势力。 为了克服这种极端条件，已经提出，数百万多年来的大气二氧化碳浓度必须使其目前的库存增加了100倍，最终建立了足够的温室气体以温暖冷冻的星球。 一方面，神秘的碳酸盐所需的材料（这些新元古代冰川沉积物在全球范围内限制）可能来自这种二氧化碳充电气氛的强烈风化。 另外，这些材料的来源可能是从深海中得出的，在广泛的，但较为严重和较短的冰川时期，硫酸盐还原细菌主导了水柱 - 类似于当今的缺氧黑海。 测试这两种末端的假设的有效性，都需要详细研究碳酸盐含量的元素，矿物学，质地和稳定的同位素组成。 来自纳米比亚的Otavi组的样本（首先积聚了全球冰川的关键证据），将分析来自巴西的Bambui和Macaubas群体的同等地层。 厚，碳酸盐主导的巴西继承的区域映射和高分辨率地层研究将有助于评估试图解释前寒电的严重振荡的模型。