2022 CSDMS meeting-056


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Disentangling controls on bedrock valley morphology of the Upper Mississippi River Valley

Jedidiah Dale, (he/him),Washington University in St. Louis St. Louis Missouri, United States. jed@wustl.edu
Claire Masteller, Washington University in St. Louis St. Louis Missouri, United States.
Henry Chandler, Washington University in St. Louis St. Louis Missouri, United States.

Fluvial valley width is determined by a combination of factors including regional lithology and drainage organization, as well as regional glacial and uplift history. In both topographic analysis and numerical modeling-based studies, valley width has been observed to follow a power law scaling relationship with drainage area. Local to regional scale studies have also demonstrated the influence of lithology, differential uplift, and drainage reorganization on this relationship. Yet, significant uncertainty remains regarding how these trends extend to the scale of large river networks and how they are influenced by transient forcing. The Upper Mississippi River Valley, initially incised during the early Pleistocene, presents a case study that encompasses a wide range of valley forms likely influenced by some combination of these factors, including by not limited to Spatially variable glacial history, bedrock lithology, and punctuated drainage reorganization events. This research aims to analyze the variable contribution of lithology, downstream changes in drainage area and history of reorganization, and regional variability in glacial isostatic adjustment in determining downstream trends in valley morphology. By isolating these effects, we aim to determine whether there is an extractable signal of the conditions during initial valley incision embedded in modern valley topography. Here we present a dataset of high-resolution valley aspect ratio and curvature, paired with longitudinal trends in drainage area and bedrock lithology. This is compared with empirical expectations for valley width scaling. Preliminary analysis found an overall downstream valley widening trend, however with multiple perturbations, including narrow gorges, and locally beveled valley walls caused by a combination of lithologic transitions and differing drainage integration histories.