Collaborative Research: The Tropical Temperature History of the Cretaceous Greenhouse Interval Inferred from Tanzanian "Glassy" Foraminifera

合作研究：从坦桑尼亚“玻璃”有孔虫推断白垩纪温室区间的热带温度历史

• 批准号: 0643522
• 负责人: Liviu Giosan
• 金额: --
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-15 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0643522&HistoricalAwards=false
• 关键词: Collaborative; Research; Tropical; Temperature; History

A wealth of fossil data (terrestrial and marine) from northern and southern high latitudes provide dramatic evidence that the Cretaceous was warm. However, these fossils provide incomplete snapshots of Cretaceous climate as their occurrences are discontinuous and their distributions do not provide a quantitative measure of Earth's temperature. A more continuous history of Earth's temperature change during the Cretaceous can be inferred from delta18-O ratios preserved in the Calcium Carbonate (CaCO3) shells of foraminifera. Unfortunately, interpreting paleotemperatures from delta18-O measurements is complicated by diagenesis and uncertainties regarding the delta18-O composition of contemporary seawater. Discovery of new sites that yield Cretaceous foraminifera with truly exceptional preservation has helped address diagenetic concerns, and parallel analyses of magnesium-calcium (Mg/Ca) ratios can help separate seawater and temperature effects on measured delta18-O values. This proposal requests funds to collect, isolate, and analyze exceptionally well preserved foraminifera from up to 1150 m of Late Cretaceous cores from four key stratigraphic intervals at four localities in coastal Tanzania. Results generated will greatly improve temporal and spatial control of the Cretaceous tropical temperature record. Such improvement is necessary to advance our understanding of the linkages between climate forcing mechanisms, ocean circulation, and patterns of biotic evolution and extinction in the Cretaceous greenhouse world. In combination with climate model experiments, this grant will test hypotheses regarding greenhouse climate dynamics including tropical temperature history, purported greenhouse glacial episodes, and the degree to which tropical and 'global' temperatures co-vary. This project focuses on 1) delta18-O analyses of exceptionally well-preserved foraminifera across Late Cretaceous intervals of extreme warmth and relative cold including glacial intervals, 2) parallel measurements of Mg/Ca in selected samples to help constrain changes in seawater composition, and 3) climate model experiments and data-model comparisons that will allow better evaluation of model sensitivity to Carbon Dioxide (CO2). Broader Impacts: The project involves partners from the United States (Smithsonian Museum of Natural History, University of Missouri-Columbia, and Woods Hole Oceanographic Institution), the United Kingdom (Cardiff University, Bristol University, Southampton University, and University College London), the Republic of Ireland (Trinity College Dublin), and the Tanzania Petroleum Development Corporation. The project has held regular science meetings and has enhanced the involvement of Tanzanian scientists. Graduate and undergraduate students are involved in all phases of this research, and the analyses are done at an NSF-funded stable isotope facility. Local Tanzanians are hired to support many aspects of field work. An additional benefit is improvement in the knowledge of the structural geology and stratigraphy of the southeast coastal region of Tanzania, which is useful for Tanzanian environmental policy decisions including possible hydrocarbon potential and drilling of shallow water wells.

来自北部和南部高纬度的大量化石数据（陆地和海洋）提供了巨大的证据，表明白垩纪很温暖。但是，这些化石提供了白垩纪气候不完整的快照，因为它们的发生是不连续的，并且它们的分布无法对地球温度的定量度量进行定量度量。白垩纪期间地球温度变化的更连续历史可以通过在有孔虫的碳酸钙（CACO3）壳中保留的Delta18-O比推断出来。不幸的是，从Delta18-O测量中解释古植物，这对于当代海水的Delta18-O组成的成分和不确定性使其复杂化。发现具有真正特殊保存的白垩纪有孔虫的新地点有助于解决成岩的问题，并且对镁钙（mg/ca）比率的并行分析可以帮助分离海水和温度对测得的Delta18-O值的影响。该提案要求资金收集，隔离和分析从坦桑尼亚沿海四个地区的四个关键地层间隔中的四个关键地层间隔到最高1150 m的白垩纪岩心，从最高到1150 m保存完好的有孔虫。产生的结果将大大改善白垩纪热带温度记录的时间和空间控制。这种改进对于促进我们对白垩纪温室世界中生物进化和灭绝的气候强迫机制，海洋循环和灭绝模式之间的联系是必要的。结合气候模型实验，该赠款将测试有关温室气候动态的假设，包括热带温度历史，所谓的温室冰川发作以及热带和“全球”温度共同变化的程度。该项目的重点是1）delta18-O在极端温暖和相对冷的白垩纪晚期间隔中对特殊保存完好的有孔虫的分析，包括冰川间隔，2）Mg/ca在选定样品中的平行测量，以帮助限制海水组成的变化，并允许对模型的模型进行限制，以使模型模型的变化能够限制。 （CO2）。更广泛的影响：该项目涉及美国的合作伙伴（史密森尼自然历史博物馆，密苏里州哥伦比亚大学和伍兹霍尔海洋学机构），英国（加入了布里斯托大学，布里斯托尔大学，南安普敦大学和伦敦大学学院），爱尔兰共和国（爱尔兰共和国学院）（三位一体学院）（三位一体学院）和Tanzania petrolemum petrolemum petrolemum petrolemum petrolemum petrolemummum petrolemum petrolemummum opperiation Corporiation。该项目定期举行了科学会议，并加强了坦桑尼亚科学家的参与。研究生和本科生参与了这项研究的所有阶段，分析是在NSF资助的稳定同位素设施中进行的。聘请当地的坦桑尼亚人来支持现场工作的许多方面。另一个好处是改善了坦桑尼亚东南沿海地区的结构地质和地层的知识，这对于坦桑尼亚的环境政策决策有用，包括可能的碳氢化合物潜力和浅水井的钻探。