Global (latitudinal) variation in submarine channel sinuosity: REPLY

Current classifications of submarine channels and fans link channel sinuosity to gradient, and in turn to sediment caliber, with end members being high-sinuosity, low-gradient, fine-grained systems and low-sinuosity, high-gradient, coarse-grained systems. However, the most sinuous modern submarine channels, such as the Amazon, Bengal, Indus, and Zaire, along with ancient sinuous submarine channels, are located in equatorial regions. Here we quantitatively compare slope versus latitude controls on submarine channel sinuosity and show that the latitudinal control is strong, while that of slope is weak. Variation in sinuosity with latitude is shown to occur uniquely in submarine channels; no comparable relationship is observed for terrestrial river channels. Possible causal mechanisms for this latitudinal variation are explored, focusing on the influence of the Coriolis force, flow type, and sediment type. Although climate does not vary straightforwardly with latitude, climatic controls on flow and sediment type may explain some of the latitudinal variation; Coriolis force, however, varies with latitude alone and produces an excellent fit to the observed sinuosity-latitude distribution. Regardless of which control predominates, latitudinal global variation in channel sinuosity should have changed over geologic time. Since deposit architecture and facies are linked directly with sinuosity, submarine channel deposits should also systematically vary in space and time.