Modeling the influence of sediment, climate, and tectonics on the incision of bedrock channels through highly soluble strata

模拟沉积物、气候和构造对高可溶地层切入基岩通道的影响

• 批准号: 1226903
• 负责人: Matthew Covington
• 金额: $ 26.28万
• 依托单位: University of Arkansas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-10-15 至 2016-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1226903&HistoricalAwards=false
• 关键词: Modeling; influence; sediment; climate; tectonics

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.

最近的工作在地貌学的重点是了解切割过程中的基岩渠道。然而，在许多方面，岩性和切口之间的关系仍然没有量化。特别是，化学风化通常被忽略时，建模流切口。虽然这对于风化速率相对较低的岩性可能是合理的，但对于高度可溶的岩性（如碳酸盐岩）可能会导致重大错误，碳酸盐岩在世界许多山脉中很常见。与基岩通道模型相比，目前这一代的洞穴生成模型，模拟洞穴在可溶性地层中的形成，只考虑溶解过程，忽略了机械侵蚀和沉积的影响。 因此，这两个群体内部的共同假设之间存在着严重的脱节。该项目将开发一个通过可溶解地层切割基岩通道的机械模型。该模型将包括溶解、泥沙输运和分布在河道横截面上的机械侵蚀的公式，并将受流量和泥沙供应随机变化的影响。该模型将用于检验以下假设：1）对机械和化学过程相对重要性的控制，2）决定河道宽度的因素，3）泥沙对洞穴形态的影响。该模型将进一步用于探索河流岩溶地形中地表和地下通道之间地貌工作的划分。基岩的切割过程在确定山脉的起伏和确定景观对构造和气候的响应方面起着至关重要的作用。 然而，目前大多数基岩渠道的切口模型不考虑化学侵蚀过程的影响。 这些过程在含有高溶解性岩石（如石灰石或石膏）的景观中尤为重要。基于忽略化学过程的模型的解释可能会在含有此类岩石的环境中得出错误的结论。此外，在高溶解性岩石中形成的洞穴提供了地质时间尺度上气候和景观演变的宝贵记录。洞穴通道的横截面往往保存了很长的切割记录。洞穴内的沉积物和废弃化石层包含了过去气候条件和景观响应的信息。在这项工作中开发的模型将有助于这些记录的解释。因此，通过改进洞穴记录的解释，目前的工作将导致更清楚地了解景观对气候变化和人为力量的反应。此外，大约20-25%的世界人口依赖于可溶性岩石中形成的含水层的饮用水，对洞穴形成过程和沉积物通过这些含水层的运输的更好的了解将提供可用于改善这些脆弱资源的管理的信息。 在推广方面，该项目将与当地科学中心合作，为来自多个州的年轻学生提供体验式科学教育，并帮助他们开发有关洞穴和景观演变的课程。此外，该项目还将培养一名博士后学者。