Interactions between alluvial fans and axial rivers in Yukon, Canada and Alaska, USA
Philip T. Giles, Bryce M. Whitehouse, Efthimios Karymbalis, 2018. "Interactions between alluvial fans and axial rivers in Yukon, Canada and Alaska, USA", Geology and Geomorphology of Alluvial and Fluvial Fans: Terrestrial and Planetary Perspectives, D. Ventra, L. E. Clarke
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In contrast with the archetypal definition of an alluvial fan, this study shows that fans interacting with axial rivers in Yukon and Alaska commonly exhibit asymmetrical morphology in planform. Hypothesis tests relating to the geomorphological characteristics of these alluvial fans were conducted on a dataset of 63 fluvial-dominated fans. A significant relationship existed between fan asymmetry and the direction of axial river flow, which was attributed to two factors supported by examples: (1) axial rivers have a propensity to trim the toes on the up-valley sides of fans; and (2) axial river channels are deflected across the broad valley floors, which allows the profiles on the down-valley sides of fans to be longer than on the up-valley sides. However, an asymmetrical planform morphology does not lead to a significant bias in the spatial distribution of surface streams towards the up-valley sides of fans, which typically have shorter profiles from apex to boundary. If the asymmetry in fan morphology is preserved in the sedimentary record, then the interpretation of fan deposits that developed in broad valleys and that interacted with axial rivers would be improved by understanding this modern analogue.
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Alluvial and fluvial fans are the most widespread depositional landform bordering the margins of highland regions and actively subsiding continental basins, across a broad spectrum of tectonic and climatic settings. They are significant to the local morphodynamics of mountain regions and also to the evolution of sediment-routing systems, affecting the propagation and preservation of stratigraphic signals of environmental change over vast areas.
The volume presents case studies discussing the geology and geomorphology of alluvial and fluvial fans from both active systems and ancient ones preserved in the stratigraphic record. It brings together case studies from a range of continents, climatic and tectonic settings, some introducing innovative monitoring and analysis techniques, and it provides an overview of current debates in the field.
This volume will be of particular interest to geologists, geomorphologists, sedimentologists and the general reader with an interest in Earth science.