Doctoral Dissertation Research: The Origin and Development of Cryoplanation Terraces

博士论文研究：冰冻梯田的起源与发展

• 批准号: 1817665
• 负责人: Frederick Nelson
• 金额: $ 1.66万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2019-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1817665&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Origin; Development

This doctoral dissertation research project will determine the age and development rates of cryoplanation terraces, terraces formed through the erosive action of snow and frost. Cryoplanation terraces are large upland landform features that give the impression of gigantic staircases, found in periglacial, or cold but nonglacial environments. Although these elevated bedrock terraces have been identified and discussed in scientific literature for more than a century, debate continues about the nature of the processes responsible for their formation. Development rates, calculated from dates of rock exposure across terrace treads, will be used to test one of the more prominent hypotheses advanced in the literature. This hypothesis states that these terraces are formed through intensified erosion associated with snowbanks that last well into the summer months. Recent methodological developments in geochemistry, specifically the method known as cosmogenic nuclide dating, will provide the infusion of contemporary technology necessary to make progress on this long-standing scientific issue, and has the potential to make transformative advances in the understanding of landscape development in periglacial regions. Results from this research will be shared with the U.S. National Park Service and used to enhance park management as well as the experiences of park visitors through development of interpretive displays and trail guides in several national parks and monuments. Further, the project will enable a graduate student to establish an independent research career.The great antiquity of cryoplanation terraces makes terrestrial cosmogenic nuclides the most appropriate dating method for determining their age and rates of development. Rock samples for cosmogenic nuclide dating were collected from two locations in the interior of Alaska using a transect-based sampling strategy across individual terrace treads. Dating the exposure of the clastic rocks (clasts) will facilitate calculation of erosion rates for individual terraces, and can be compared to known erosion rates at existing late-lying snowbanks. The PIs hypothesize that: (a) calculated development rates will be comparable with those of measured snowbank erosion; (b) exposure dates for individual rock clasts will coincide with Quaternary cold intervals; and (c) terrace treads are time-transgressive surfaces with the exposure age of clasts increasing toward the outer edge of terraces. The landforms in this region where the rocks for this analysis were collected are representative of those in the much larger domain of unglaciated landscapes of the Northern Hemisphere. Therefore, the methodologic and analytic approach adopted for this project are potentially applicable throughout this vast region.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该博士学位论文研究项目将确定冷冻梯度露台的年龄和发展率，这是通过雪和霜冻的侵蚀作用形成的露台。冷冻恒温露台是庞大的高地地面特征，它给人以巨大的楼梯的印象，即在冰期或寒冷但不冰的环境中发现。 尽管在科学文献中已经确定和讨论了这些高架基岩露台，但在一个多世纪中，辩论仍在继续辩论。 开发率是根据遍布露台胎面的岩石暴露日期计算得出的，将用于测试文献中最突出的假设之一。 该假设指出，这些露台是通过与雪库相关的加剧侵蚀形成的，持续到夏季。 地球化学方面的最新方法论发展，特别是称为宇宙核素约会的方法，它将提供在这个长期存在的科学问题上取得进步所必需的当代技术，并有可能在理解近核区域景观发展方面取得变革性的进步。 这项研究的结果将与美国国家公园管理局分享，并通过在几个国家公园和古迹中开发解释性展示和越野指南来增强公园管理以及公园游客的经验。 此外，该项目将使研究生能够建立独立的研究职业。冷冻恒温阶地的伟大古代使陆地宇宙核素成为确定其年龄和发展速度的最合适的约会方法。 从单个露台胎面跨越基于样带的采样策略，从阿拉斯加内部的两个位置收集了宇宙核素年代的岩石样品。 日期的碎屑岩石（碎屑）的暴露将有助于计算单个露台的侵蚀率，并可以将现有晚期雪岸的已知侵蚀率进行比较。 PI假设：（a）计算出的开发率将与测量的雪库侵蚀相媲美； （b）单个岩石碎屑的暴露日期将与第四纪冷间隔一致； （c）露台胎面是时间转换的表面，碎屑的暴露年龄朝向露台的外边缘。 在该地区收集了该分析的岩石的地形代表了北半球未接种景观范围内的岩石。 因此，该项目采用的方法论和分析方法可能在整个地区都适用。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响审查标准通过评估来支持的。