Late cenozoic of the Canadian Arctic archipelago and the southern central Andes

我对地球景观在不同时间尺度上的演变很感兴趣。在数千年至数亿年的时间尺度上，两种确定地表过程速率和时间的时间顺序方法正在彻底改变地球科学家分析景观演变的方式。当宇宙射线与地球表面上方几米暴露的矿物相互作用时产生的地球宇宙核素（tns）被用来直接确定景观变化事件发生的时间，例如过去冰川作用的时间，基岩表面或冲积扇等应力标志的地震偏移，或火山爆发的时间。切割的峡谷壁和基岩沟阶地的暴露年龄可以提供有关选定河段切割速率变化的信息。此外，tcn还可用于估算从单个山峰到整个河流集水区在数千年至数百万年时间尺度上的短期和长期平均侵蚀速率。第二种方法是(U-Th-Sm)/He低温热年代学，用于估计从2至4公里深处挖掘出来的地球表面岩石的冷却历史（矿物在上升过程中可能以不同的速度冷却）。这项技术适用于数万年到数亿年的时间尺度，也可以用作温度年代学工具（测定史前火山灰中的矿物年代）。结合这两种方法的优点是可以获得对景观演变的更全面的了解，以便解决以下问题：(1)安第斯山脉地震断层的历史是什么？(2)加拿大盾构（潜在核废料储存库）的侵蚀历史如何？(3)整个北极中部广阔的地貌表面的进化史是什么？这个问题的答案有助于降低北极石油和矿产勘探的风险。这些技术的设施已经在达尔豪斯建立，我的研究项目将帮助培养同位素和环境地球化学方面的本科生和研究生、技术人员和访问研究人员。

I am interested in how Earth's landscapes have evolved over different timescales. Two chronological methods for determining rates and timing of surface processes at timescales between thousands and hundreds of millions of years are revolutionizing the way Earth Scientists analyse landscape evolution. Terrestrial cosmogenic nuclides (TCNs) produced when cosmic rays interact with exposed minerals in the upper few metres of Earth's surface are used to directly date when landscape change events have occurred, such as the timing of past glaciations, seismic offset of strain markers such as bedrock surfaces or alluvial fans, or the eruption of volcanoes. Exposure ages of incised canyon walls and bedrock strath terraces can provide information about the variability in incision rates of selected reaches of streams. Additionally, TCNs can be used to estimate short- and long-term averaged erosion rates of spatial scales from individual mountain peaks to entire stream catchments over timescales of thousands to millions of years. The second method, (U-Th-Sm)/He low temperature thermochronology, is used to estimate the cooling history of a rock on Earth's surface since it was exhumed from depths of two to four kilometres (minerals may cool at variable rates as they ascend). The technique is applicable over timescales of tens of thousands to hundreds of millions of years, and can also be used as a tephrochronology tool (to date minerals in pre-historic volcanic ash). The advantage in coupling both methods is that a more complete understanding of landscape evolution may be attained, in order to address questions such as: (1) What is the history of earthquake faulting in the Andes? (2) What is the erosion history of the Canadian shield (potential nuclear waste repository)? (3) What is the evolutionary history of the expansive physiographic surfaces throughout the Central Arctic? Answers to this question help reduce risk to petroleum and mineral exploration in the Arctic. The facilities for these techniques have been established at Dalhousie and my research program will help train undergraduate and graduate students, technical staff, and visiting researchers in aspects of isotope and environmental geochemistry.