Effects of base level fall and basin geometry on the morphology and stratigraphy of a coarse-grained, river dominated delta Public

Base level change and basin geometry play strong roles in determining delta morphology and stratigraphy. This study uses numerical models to test the control of the rate of relative base level fall on delta morphology and stratigraphy. Also, the study views the effects of basin slope and depth on delta morphodynamics. Five variables are used in an effort to view the controls of base level fall and basin geometry on delta growth. They also serve to validate model results by comparing numerical experiment values to the Goose River Delta, a modern, coarse-grained, forced-regressive system. Variables measured include: shoreline rugosity, the number of active distributaries, clinoform concavity, clinoform dip magnitude, and reservoir rugosity. Model results suggest increasing base level fall rates increase shoreline rugosity and the number of active distributaries but play no role in clinoform dip magnitude and plot a complex function for clinoform concavity. The model experiment meant to emulate the Goose River Delta (30 m deep basin; 6 mm/yr base level fall rate) does not share similar values or planform shape. However, a numerical delta experiencing 6mm/yr in a 3 m deep basin shows similar planform morphology. I attribute this to a lower model D50 than the Goose River Delta. Also, the models use an average discharge as opposed to the wide range of discharges the Goose River Delta experiences due to freezing over and flooding.

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