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Understanding the Stratigraphy of a Physical Model of a Cohesive Delta

William M. Benson, Qi Li, and Kyle M. Straub
Tulane University, Department of Earth and Environmental Sciences

Recent work has characterized the influence of sediment cohesion on deltaic topography and morphodynamics, however at present we lack a description of how cohesion influences stratigraphic architecture. Recent innovation in physical experiments allows for the study of linkages between surface dynamics and resulting stratigraphy. Two physical delta experiments were conducted in the Tulane Delta Basin, the sole difference between the two being the inclusion of a polymer that enhances sediment cohesion and promotes channelization from subcritical Froude number flows. Experiments were run with a base level rise that generated terrestrial accommodation at a rate equivalent to the input sediment discharge over a 900 h period. This resulted in stratigraphic packages approximately 20 channel depths thick. Here, our goal is to develop transfer functions that describe how information pertaining to paleo-topography and morphodynamics is stored in stratigraphy. Topography of the experimental surface was collected every 1 h with a LiDAR unit and used to generate digital elevation models (DEMs). Synthetic stratigraphy is then generated from stacked DEMs with topography clipped to account for sediment removed during erosion. To benchmark our synthetic stratigraphy, images of the physical stratigraphy were collected using a freeze coring technique along selected topographic transects. The cohesive delta experiment, characterized primarily by suspension fallout sedimentation, resulted in construction of stratigraphic surfaces with spatial statistics similar to the experiment’s topographic surfaces. The non-cohesive delta experiment, characterized primarily by bed load sediment transport, resulted in stratigraphic surfaces with slopes and curvatures far in excess of the experiment’s topographic surfaces.

AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013