Large-scale landscape responses to Cenozoic climatic and lithospheric processes

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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. *****