Collaborative Research: An Absolute Chronology of the Southernmost Advances of the Laurentide Ice Sheet

合作研究：劳伦太德冰盖最南端进展的绝对年代学

• 批准号: 0545518
• 负责人: John Stone
• 金额: $ 9.19万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0545518&HistoricalAwards=false
• 关键词: Collaborative; Research; Absolute; Chronology; Southernmost

Work under this collaborative will provide key information to address a long-standing issue in North American Quaternary geology: correlating continental physical evidence of repeated glaciations with the marine oxygen isotope record.To a great extent, what we know about the glaciations of the last several million years has been deduced from a proxy - rhythmic variations in d18O that reflect the balance between seawater and freshwater locked up in ice. These variations can be dated by relating them to changes in the Earth's inclination towards the Sun, and the eccentricity of the orbit - both factors which change how much energy the surface receives. However, there is little to no information on the distribution of that ice over the continental surfaces, and little information on why there are changes in ice periodicity not explained by orbital changes.Dating of glacial advances by the mapping of tills on the continent has been extremely difficult until the advent of a cosmogenic nuclide technique pioneered by this team. Beryllium-10/Aluminium-26 dating is a technique that provides resolution not provided by other chronometers. Dating of tills from Missouri northwards into Iowa will yield direct dates for at least five of the southernmost advances of the Laurentide Ice Sheet. The team will be able to provide data for questions about the role of ice sheets in Plio-Pleistocene climate, and their role in abrupt climate change.Through extensive collaboration with state geological surveys, the team will be able to transfer the technique into areas of geohydrological mapping that are interested in correlating different tills. In addition, the team has received extensive coverage for previous work on dating of fossil bearing sediments as well as the continent's oldest dated till, and expects to continue this public interest in the applications of cosmogenic nuclide dating techniques.

这项合作下的工作将为解决北美第四纪地质学中一个长期存在的问题提供关键信息：将大陆反复冰川的物理证据与海洋氧同位素记录相关联。在很大程度上，我们对过去数百万年冰川的了解是从d18O的替代韵律变化推断出来的，该变化反映了被锁在冰中的海水和淡水之间的平衡。这些变化可以通过将它们与地球向太阳倾斜的变化和轨道的偏心率联系起来--这两个因素都会改变地表接收的能量--来确定日期。然而，几乎没有关于冰层在大陆表面分布的信息，也几乎没有信息来解释为什么冰川周期的变化不是由轨道变化来解释的。通过绘制大陆上的冰层地图来确定冰川推进的日期一直是极其困难的，直到这个团队开创的宇宙成因核素技术出现之前。铍-10/铝-26测年技术提供了其他计时器所不能提供的分辨率。对从密苏里州向北进入爱荷华州的收费站进行测年，将得出劳伦蒂德冰盖最南端的至少五个冰盖的直接日期。该团队将能够为冰盖在上更新世气候中的作用以及它们在气候突变中的作用等问题提供数据。通过与国家地质调查局的广泛合作，该团队将能够将这项技术转移到对不同耕层相互关联感兴趣的地质水文测绘领域。此外，该小组还广泛报道了以前关于含化石沉积物的测年工作以及非洲大陆最古老的测年工作，并预计将继续这一公众对宇宙核素测年技术的应用的兴趣。