Postglacial landscape change in western Canada

我和我的学生们正在参与了解加拿大西部的景观是如何适应上一个冰河时期覆盖它的冰盖的迅速消亡的，以及景观是如何对随后的气候变化作出反应的。我们的主要研究是在不列颠哥伦比亚省的科迪勒兰山脉进行的，在那里，冰川沉积在山上的沉积物被留在了非常不稳定的位置，其中大部分被河流迅速侵蚀，沉积在靠近谷底的更稳定的位置。今天，这些沉积物中的许多可以被看作是占据着沿着山谷的高河流阶地上发育的大型扇形地貌（冲积扇和泥石流扇）。这些大型地貌位于脆弱的位置，因此预计对气候变化极为敏感。我的研究非常仔细地观察了这些扇形何时开始形成，何时停止形成；它还研究了它们的内部结构，以发现它们的构造模式与过去气候变化之间的联系。通过了解这一点，我们应该能够帮助预测未来气候变化将对不列颠哥伦比亚省和类似地区脆弱地貌的稳定性产生的影响。与这项研究密切相关的是我与加拿大地质调查局和莱斯布里奇大学的同事一起进行的一项研究，该研究涉及加拿大大草原的景观变化。在这种情况下，我们正在研究今天稳定的大片沙丘，但在长时间的炎热和干燥气候中变得活跃。由于在这些地形（扇形或沙丘）中找到放射性碳定年的有机物是极其罕见的，我们依靠发光定年，这使我们能够确定埋在其中的沉积物最后暴露在阳光下的时间。这种测定年代的方法是在弗雷泽谷大学的一个特殊实验室里完成的，它本质上是实验性的，实验室程序必须进行修改和测试，以适应每种情况。

My students and I are involved in understanding how the landscape in western Canada adjusted to the rapid demise of the ice sheets that covered it during the last ice age, and how the landscape has responded to subsequent changes in climate. Our principal research is done in the Cordilleran mountains of B.C. where sediment deposited in the mountains by the glaciers were left in very unstable positions, and much of it was rapidly eroded by streams and deposited in more stable positions near the valley bottoms. Many of these sediments can be seen today as occupying large fan-shaped landforms (alluvial and mudflow fans) that developed on high river terraces along valleys. These large landforms rest in fragile positions and are thus expected to be extremely sensitive to changes in climate. My research looks very carefully at when these fans started forming, and when they stopped forming; it also looks at their internal structure to find links between their mode of construction and changes in past climate. By understanding this we should be able to help predict the effect that future climate change will have on the stability of fragile landforms in British Columbia, and those in similar regions. Closely related to this study is research that I am conducting with colleagues at the Geological Survey of Canada and University of Lethbridge which involves landscape change on the Canadian prairies. In this case, we are studying large fields of sand dunes that are stable today, but become active during prolonged periods of hot and dry climate. As it is extremely rare to find organic matter for radiocarbon dating inside any of these landforms (fans or dunes), we rely on luminescence dating, which allows us to date when sediments buried within them were last exposed to sunlight. This method of dating, which is done in a special laboratory at University of the Fraser Valley, is inherently experimental, and laboratory procedures have to be modified and tested to suite each situation.