Reconstructing Landscape Evolution History Using Geological Data and Numerical Modelling

作为了解气候变化将如何影响我们生活环境的努力的一部分，景观演变的研究领域正变得越来越重要。例如，在高山山脉，了解冰川消退和永久冻土融化对侵蚀的影响，将为估计地貌灾害风险、活动断层上的地震活动和山区生态系统的生境变化提供科学依据。大山脉是由板块构造形成的，由气候雕刻而成。这些外力之间的强烈反馈使从观测数据中解释它们各自对山地景观演变的贡献变得复杂起来。数值模拟为量化地貌对变化条件的反应提供了宝贵的工具，但不同侵蚀过程的相对重要性和侵蚀模型中的主要参数都需要更好地加以限制。 我的研究项目将通过经验观察和数值方法相结合的方法，调查构造和气候条件不同的山脉的景观历史。我将使用多种热年代学方法评估这些山脉在不同时间尺度上的岩石折返和剥蚀历史。将收集基岩冷却年龄来推断构造变形模式，而沉积物来源分析将用于绘制侵蚀强度在山脉和流域尺度上的空间分布。估计的侵蚀模式将与不同侵蚀剂的分布进行比较，如冰川下切、河流切割和山体滑坡，以评估它们在改变山区景观方面的相对重要性。最后，将汇编其他经验数据集(例如，泥沙通量、流域平均侵蚀速率、气候历史)，并将其用于约束模拟自然景观历史的数值模型。通过迭代减少模型预测和观测数据之间的不匹配，模型将得到优化。 在这一资助期间，我优先考虑的领域是海岸山脉南部、不列颠哥伦比亚省和中国东部的田山。海岸山脉被反复的冰川雕刻而成。基于基岩和碎屑的热年代学，我将研究冰川-间冰期过渡期间的侵蚀模式，特别是在最后一次冰川消融期间。相比之下，中国的田山坐落在半干旱的气候带，在其北部的山前，有一系列被深深切割的河流梯田。我将估计上游侵蚀和泥沙输送和沉积过程，以了解构造抬升和气候变化如何控制下游环境中河流和冲积阶地的形成和保存。

As part of the effort to understand how climate change will impact our living environment, the research field of landscape evolution is becoming increasingly important. For example in high mountain ranges, knowing the impacts on erosion from retreating glaciers and thawing permafrost will provide a scientific basis for estimating risks of geomorphic hazards, seismicity on active faults, and habitat changes in mountain ecosystems. Large mountain ranges are created by plate tectonics and sculpted by climate. The strong feedbacks between these external forcings complicate the interpretation of their respective contribution to mountain landscape evolution from observational data. Numerical modelling provides a valuable tool for quantifying how landscapes respond to changing conditions, but both the relative importance of different erosion processes and the main parameters in the erosion models need to be better constrained. My research program will investigate the landscape histories of mountain ranges with contrasting tectonic and climatic conditions, by combining empirical observation and numerical methods. I will evaluate the rock exhumation and erosion histories of the mountain ranges over different time scales using multiple thermochronological methods. Bedrock cooling ages will be collected to infer the tectonic deformation pattern, whereas sediment provenance analysis will be applied to map the spatial distribution of the erosion intensity on mountain and catchment scales. The estimated erosion pattern will be compared to the distribution of rates of different erosion agents, such as glacial downcutting, fluvial incision, and landslides, in order to assess their relative significance in transforming the mountain landscape. Finally, other empirical datasets (e.g., sediment flux, basin-averaged erosion rate, climate history) will be compiled and used to constrain numerical models that simulate the history of a natural landscape. The models will be optimised by iteratively reducing the misfits between the model predictions and the observed data. For this funding period, my prioritised field areas are the southern part of the Coast Mountains, British Columbia and the eastern Chinese Tian Shan. The Coast Ranges were carved by repeated glaciations. Based on bedrock and detrital thermochronology, I will investigate the erosion patterns during the glacial-interglacial transitions, especially during the last deglaciation. In contrast, the Chinese Tian Shan sits in a semiarid climate zone, featuring a series of deeply incised river terraces on its north piedmont. I will estimate the upstream erosion and sediment transport and deposition processes, in order to understand how tectonic uplift and climate change control the formation and preservation of the fluvial and alluvial terraces in the downstream environment.