The structure of many continental margins reflects a competition between the dynamics of mobile substrates that can produce bathymetric depressions (i.e., minibasins) and the depositional mechanics of turbidity currents that fill depressions. Depending on parameters that define minibasin geometry and the sediment transport capacity of turbidity currents, flows either get trapped or can (partially) surmount a minibasin and continue downslope. Prior experiments quantified this fill-to-spill transition in 2D, but we lack detailed knowledge of the depositional mechanics of these flows in 3D. We explore these dynamics in physical experiments where we release 3% excess density flows that are Froude critical into a circular minibasin with 10% side wall slopes and a basin depth that is 2.5 times the input flow height. Over a sequence of experiments, we alter the input flow width, and thus the flux of sediment released into the basin. This drives responses that span the fill (i.e., sediment deposited in basin equals sediment released to basin) to spill (<50% trapping of input sediment) transition. We collect time lapse photography, repeat surveys of topography, time series of sediment concentration and velocity at basin center, and maps of the 3D flow structure during equilibrium conditions. Initial results identify and define the structure of recirculation cells that distribute sediment in ponded flow. We also observe a link between input sediment flux, the equilibrium structure of velocity and sediment concentration profiles, and the resulting onlapping height of turbidites with basin walls. Specifically, greater influx rates result in less sediment stratification and greater onlapping heights.