| Levee architecture of six submarine channel-levee systems was investigated using seismic reflection profiles, piston cores, and boreholes. The systems span a wide range of geological environments and comprise the Northwestern Atlantic Mid-Ocean Channel (NAMOC), and Hueneme, Reserve, Amazon, Var, and Laurentian fans. Quantitative measures of architecture were defined and used to investigate the spatial and stratigraphic evolution of levees. Depositional sequences on levees display regular variations in thickness both across-levee and downchannel. Perpendicular to channel trend, depositional sequences thin following an exponential trend that can be quantified by a spatial decay parameter, k. Along the upper reaches of a system, downchannel exponential thinning of levee sediment is quantified by a second spatial decay parameter, λ. Stratigraphically, the growth of sediment waves and the evolution of levee crests followed consistent patterns not previously recognized. No significant stratigraphic pattern was observed for k.; Characterization of thickness variations using k and λ allows the direct comparison of levee architecture and channel morphology. Using data from all the systems investigated, correlations were found between the inverse of k and both channel half-width, W, and channel relief, D, and between the inverse of λ and W and D. Based on the downchannel behaviour of k and sediment thickness at the levee crest, submarine channels divide into two discrete reaches: an upper reach where k is uniform and sediment thickness decays exponentially downchannel, and a lower reach where k tends to decrease and sediment thickness is uniform or decays abruptly in the downchannel direction.; The channel-levee systems studied here have a wide range of sediment sources and different mechanisms for flow initiation. Nevertheless, levee architecture correlates with channel morphology, suggesting that flow processes rather than external conditions control this architecture. A simple model of flow behaviour suggests reasons for the observed geometric relationships provided that channel geometry relates to throughchannel volume discharge in a manner analogous to the relationships between channel geometry and volume discharge established for rivers. |
