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.

摘要新元古代冰河时代的生物地球化学后果这项研究旨在严格检验著名的雪球地球假说，该假说预测，在新元古代（543-10亿年前），整个地球多次被大陆冰川和冰盖覆盖，从两极到赤道。海冰。 为了克服这种极端条件，有人提出，数百万年来，大气中的二氧化碳浓度必须上升到目前库存的 100 倍以上，最终产生足够的温室气体来温暖这个冰冻的星球。 一方面，神秘的碳酸盐（覆盖着全世界新元古代冰川沉积物）所需的材料可能来自大陆在这种充满二氧化碳的大气下的强烈风化。 或者，这些物质的来源可能来自深海，在广泛但不太严重和较短的冰川时期，硫酸盐还原细菌在水柱中占主导地位 - 类似于现在的缺氧黑海。 检验这两种端元假说的有效性都需要对盖帽碳酸盐的元素、矿物学、结构和稳定同位素组成进行详细研究。 纳米比亚奥塔维群（全球冰川作用的关键证据首先在此收集）以及巴西班布伊群和麦考巴斯群明显相当的地层样本将进行分析。 对厚厚的、以碳酸盐为主的巴西地层进行区域测绘和高分辨率地层研究将有助于评估旨在解释前寒武纪气候剧烈波动的模型。