Isostatic Control of Axial Rivers and Large Drainage Basins on Passive Margins

More than half of the world's large rivers flow towards the ocean crossing passive continental margins. Here using an analytical solution and numerical models, we demonstrate that on passive margins, river basins may be integrated by major margin-parallel channels, which form as a flexural isostatic response of the lithosphere to mechanical/erosional unloading along the margin. We analyzed the downstream courses of large rivers flowing across the passive margins and find that the majority of them (31 of 36) have major margin-parallel channels. Occurrences of these channels are generally consistent with the model predictions, although the exact locations and geometry of these rivers may also be controlled/changed by other factors. Our results suggest that the lithosphere strength has an important control on the geometry of large river systems on passive margins, linking the evolution and routing of the Earth's freshwater systems to its deep interior dynamics.