Geometric Variations Between Deltaic Distributary Channels and Preserved Channel Bodies: Using Experimental Deltas to Link Surface Morphodynamics to Subsurface Architecture

Characterization of subsurface channel body geometries is critical to assessing natural resources and efficiency of subsurface fluid transport. In deltaic environments, distributary channel networks serve as the primary conduits for water and sediment. When these surface channels are buried and translated into the subsurface, coarse-grained paleo-channel bodies can serve as reservoirs or conduits for groundwater, contaminants, and hydrocarbons. Hence, it is essential to understand the ways in which surface channel geometries are translated into subsurface paleo-channels. Typically, preserved channel bodies are larger than surface channels due to vertical aggradation and lateral migration of surface channels. Here we investigate the geometric variation of active dynamic channels and preserved static channels using data from the XES02 laboratory experiment, which includes overhead imagery, topographic scans, and cross-section imagery. The XES02 experiment was designed to investigate the effect of base-level cycles on shoreline behavior and it used a quartz and charcoal sediment mixture, which developed into a braided channel network. We compare the dimensional properties (i.e. depth and width) of active and preserved channels and attempt to link between them. We also evaluate the variations in subsurface channels filled by coarse- versus fine-grained sediment, and between rapid and slow aggradation phases. This study suggests that the degree of geometric change of preserved distributary channel bodies can be affected by type of sediment and rate of aggradation.