Spatial Variability in Meander Characteristics Within Modern Distributive Fluvial Systems (DFS)

Fluvial systems support a large variety of habitats, are important biogeochemical interfaces and act as conduits for delivering sediment and water to seas and oceans, as well as forming political boundaries. Fluvial sandstone deposits have the potential to act as reservoirs for carbon capture and storage and form the basis of geothermal and freshwater aquifers. Therefore, understanding the lithological variation of such deposits is critical to enhancing natural resource exploration and the sequestration of carbon from our atmosphere, in addition to providing insight into modern fluvial geomorphic processes.

Recent research suggests that the abundance of subsurface fluvial deposits, such as meander deposits, have been significantly under-estimated within sedimentary basins. Therefore, meander deposits may form a bigger proportion of the rock record than previously thought. Research is required to better understand the spatial variation in gross-scale meander system characteristics, such as meander size and deposit architecture.

This project aims to bridge these knowledge gaps by studying both modern and ancient meander deposits within a spatial context, by exploring how meander characteristics vary within and across two sedimentary basin types within different climatic settings. This will provide new quantification of the spatial variability expected within subsurface deposits and provide further understanding of fluvial geomorphic processes within sedimentary basins. The Meander Statistics Toolbox (MStaT - Ruben et al., 2021) was used alongside GIS and Google Earth Engine (GEE) to extract a range of meander characteristics (e.g. meander sinuosity, amplitude and migration rate) from modern DFS. Results from the Wood River DFS, Alaska, indicate that meander characteristics vary spatially, however not all characteristics follow a distinct downstream trend. The active channel width of the DFS is found to decrease downstream as expected based on literature (e.g. Nichols and Fisher, 2007; Weissman et al., 2010), however the channel belt width shows no clear downstream trend. Characteristics such as meander sinuosity and amplitudes are found to increase downstream to the medial zone of the DFS, and decrease towards the distal region. Meander migration rates follow a decreasing downstream trend from proximal to distal regions of the DFS. Comparison with the Bermejo DFS, Argentina will indicate how these compare to a different geographical and basin setting.

The implications of this research are as follows: 1) to further understand modern fluvial geomorphic processes; 2) to provide new quantification for the variability expected within subsurface deposits and 3) to enhance understanding of the lithological variation of deposits for natural resource exploration and carbon sequestration.