How Depositional Slope and Sediment Concentration Influence the Morphology of Deepwater Turbidite Lobe Systems

Confinement, basin slope, local topography, and sediment supply are major factors controlling the dimensions of individual turbidites and submarine lobes. The same factors that control individual turbidites and lobes are also likely to influence the larger-scale submarine fan morphology, however lobe dimensions can vary even within a single submarine fan. This study focuses on how sediment concentration and basin gradient affect the morphology of turbidite lobe elements, and whether lobe element morphology scales with the morphology of the larger lobe complex over time. A series of physical laboratory experiments were conducted in a 4 x 4 x 1 m basin and experiments were imaged with overhead time-lapse photography and a submersible topographic scanner. Experiments covered a range of sediment concentrations (5–10%) and basin gradients (3°–7°) while holding scaled sediment type (crushed glass), grain size (ranging 20–700 μm, with average D50 105 μm), discharge and fluid density constant. Each set of experiments comprised five turbidity currents with the same parameters to build a composite lobe. Experimental results are compared with subsurface data from the Moki Formation, a submarine fan system in the Taranaki Basin, New Zealand. Comparison of 3D mapping of subsurface seismic and well data from the Moki Formation with the experimental results allows for an analysis of deepwater fan-lobe systems at a variety of scales.