Recent work in geomorphology has focused on understanding incision processes in bedrock channels. However, in many aspects, the relationships between lithology and incision remain unquantified. In particular, chemical weathering is typically ignored when modeling stream incision. While this may be reasonable for lithologies that exhibit a relatively low rate of weathering, it may lead to significant errors for lithologies that are highly soluble such as carbonates, which are common in many of the world's mountain ranges. In contrast to bedrock channel models, the current generation of speleogenetic models, which simulate the formation of caves in soluble strata, consider only the dissolution process and neglect the effects of mechanical erosion and sediment. Therefore there is a crucial disconnect between the common assumptions within the two communities. This project will develop a mechanistic model for the incision of bedrock channels through soluble strata. The model will include formulations for dissolution, sediment transport, and mechanical erosion distributed across channel cross sections and will be forced with stochastic variations in discharge and sediment supply. The model will be used to test hypotheses concerning: 1) the controls on the relative importance of mechanical and chemical processes, 2) the factors that determine channel width, and 3) the influence of sediment on cave form. The model will be further employed to explore the partitioning of geomorphic work between surface and subsurface channels in fluviokarst terrain.
The incision processes in bedrock play a crucial role in setting the relief of mountain ranges and determining the response of landscape to tectonics and climate. However, most current models of incision in bedrock channels do not consider effects of chemical erosion processes. These processes are particularly important in landscapes containing highly soluble rocks, such as limestone or gypsum. Interpretations based on models that ignore chemical processes may lead to faulty conclusions in settings containing such rocks. Additionally, the caves that form in highly soluble rocks provide valuable records of climate and landscape evolution over geological time scales. Cave channel cross sections often preserve long records of incision. Sediment deposits and abandoned fossil levels within caves contain information about past climate conditions and landscape response. The model developed in this work will aid in the interpretation of such records. Therefore, through improved interpretations of cave records, the current work will lead to clearer understanding of the response of landscape to climate change and anthropogenic forces. Furthermore, approximately 20-25% of the world's population depends on drinking water from aquifers formed in soluble rocks, and an improved knowledge of the process of cave formation and transport of sediment through these aquifers will provide information that can be used to improve management of these fragile resources. With respect to outreach, the project will work with a local science center that provides experiential science education for young students from a multi-state area, and help them to develop curricula concerning caves and landscape evolution. In addition, the project will train a postdoctoral scholar.
