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Translating Between the Surface and Subsurface: Inversion of Stratigraphy for Paleo-Topographic Statistics


Recent work has demonstrated differences between topography and resulting stratigraphic surfaces at various spatial resolutions, however at present we lack a description of how channel mobility influences stratigraphic architecture. Our goal is to develop transfer functions that describe how information pertaining to paleo-topography and morphodynamics is stored in stratigraphy. Physical experiments allow for the study of linkages between surface dynamics and resulting stratigraphy. To better understand these transfer functions we will examine two physical delta experiments, the sole difference between the two being the inclusion of a polymer that enhances sediment cohesion and promotes channelization from subcritical Froude number flows. The increased channelization reduces the channel mobility, thus allowing for floodplain deposition through suspension fallout of sediment in overbanking flow. Experiments are run with a base level rise that generated terrestrial accommodation at a rate equivalent to the input sediment discharge over a time period sufficient to aggrade 18 channel depths worth of stratigraphy. Topography of the experimental surface was collected at a high temporal resolution relative to channel kinematics and used to generate digital elevation models (DEMs). Synthetic stratigraphy is then generated from stacked DEMs by clipping topography to account for sediment removed during erosion. To benchmark our synthetic stratigraphy, images of the physical stratigraphy were collected along selected topographic transects. Results from the strongly cohesive delta experiment, demonstrate construction of stratigraphic surfaces with spatial statistics similar to the experiment's topographic surfaces. Initial observations from the second, non-cohesive experiment include shallower channels with enhanced lateral mobility relative to the cohesive experiment. Spatial statistics of topography and resulting stratigraphy will be compared at various resolutions in order to quantify and understand the differences.