Large-scale landscape responses to Cenozoic climatic and lithospheric processes

地球宇宙核素（TCN）是宇宙射线粒子与岩石中的原子相互作用产生的。它们的浓度被用来确定地球表面或地球表面附近自然过程的时间、速率和类型。拟议的研究计划旨在(i)测试一种原始和创新的方法，该方法使用从地下数百米的宇宙成因μ子产生的同位素来确定地形如何在数百万年的时间里演变，我们称之为μ子古地形测量学；（ii）扩大我们对加拿大发生的最大景观演变之一的认识，以及它对北极未来变化的影响。***(i) μ子古地形测量是可以实现的，因为最近我们对宇宙产生的μ子如何与原子相互作用的理解有了新的进展，化学和分析方法也有了新的改进。为了测试这种方法，我们在众多（备用）地点中选择了两个地点，在那里，隧道提供了几十个地下样本，需要解决一个有趣的问题。在瑞士，一个多世纪的研究旨在确定导致欧洲阿尔卑斯山脉起伏的过程。虽然其他技术可以提供一些见解，但μ子古地形测量法将确定地形是否主要由过去2千万年的冰川侵蚀引起，或者是否大部分地形是由于早期构造或气候因素而继承自河流切割。在第二个地点，犹他州的科罗拉多河形成了一个巨大的下沉洞，造成了200米的悬崖。悬崖形成事件的~1.7 Myr年龄是独立的，该遗址为探索阿尔伯塔省南部等峡谷地和荒地的悬崖侵蚀方式和速度提供了机会。***(ii)根据我们之前NSERC的研究结果，我们假设加拿大北极群岛在2.7 Myr之前还不存在，该地区被一层厚厚的上新世（5.3至2.7 Myr）流砾石覆盖，这些砾石后来被侵蚀。最近，西北航道因侵蚀而非构造作用而开放，这可能会对加拿大的说法产生影响，即西北航道是相邻大陆内的内水。我们寻求(a)提高我们对上新世水系沉积物来源附近的知识（在埃尔斯米尔群岛的野外工作）；(b)利用在加拿大北极中部基岩中测量的TCN比率来确定倾斜的、冰川前的基岩表面是否表现出上新世的埋藏信号；(c)通过TCN埋藏年代测定和生物地层学分析表明，Bylot Is上的小袋溪流砾石是曾经广泛覆盖的上新世沉积物的残留物。***这些目标以及实验室和方法发展的数量将涉及加拿大和国际合作者，并培养2名博士，2名硕士，1名pdf，本科生，他们将成为国际和北极研究，同位素化学，景观对气候变化的敏感性和科学传播方面的知识分子。* * * * *

Terrestrial cosmogenic nuclides (TCN) are produced when cosmic ray particles interact with atoms in rock. Their concentrations are used to establish the timing, rates, and styles of natural processes on or near Earth's surface. The proposed research program aims to (i) test an original and innovative method that uses isotopes produced from cosmogenic muons hundreds of metres underground to establish how topography evolved over millions of years, we call it muon paleotopometry, and (ii) expand our knowledge of one of the largest landscape evolutions that have occurred in Canada, and its implications for future change in the Arctic. ***(i) Muon paleotopometry is achievable because of recent developments in our understanding of how cosmogenic muons interact with atoms and recent improvements in chemistry and analytical methods. To test the approach, we have selected two locations among numerous (backup) sites, where tunnels provide access to dozens of underground samples needed to solve an interesting question. In Switzerland, over a century of research has aimed at determining the processes responsible for the relief of the European Alps. While other techniques can provide some insight, the muon paleotopometry will determine if the topography is mostly caused by glacial erosion in the past 2 Myr, or if much of the relief was inherited from stream incision in response to earlier tectonic or climate factors. At the second location, a large sink-hole collapse left a 200-m escarpment as relief was being created by the Colorado River in Utah. The ~1.7 Myr age of the scarp-forming event is known independently and the site provides an opportunity to explore how and how fast scarps erode in canyonlands and badlands such as in southern Alberta.***(ii) From results of our previous NSERC research, we hypothesize that the Canadian Arctic Archipelago did not exist as recently as 2.7 Myr ago, and that the region was covered by a thick layer of mostly Pliocene (5.3 to 2.7 Myr) stream gravels which have since been eroded. A recent opening of the Northwest Passages by erosion, not tectonics, may have implications for Canada's claim that they are internal waters within an otherwise contiguous landmass. We seek to (a) improve our knowledge of the Pliocene stream sediments near their sources (field work on Ellesmere Is.); (b) use ratios of TCN measured in bedrock in central Arctic Canada to determine if tilted, pre-glacial bedrock surfaces exhibit a Pliocene burial' signal; and (c) show that pockets of stream gravels on Bylot Is are remnants of the once extensive Pliocene sediment cover by TCN burial dating and biostratigraphy.***These goals and number of lab and methodological developments will involve Canadian and international collaborators, and train 2 PhD, 2MSc, 1PDF, undergraduates who will become knowledgeable in international and Arctic research, isotope chemistry, the sensitivity of landscapes to climate change, and science communication. *****