Creep in pelagic sediments and potential for morphologic dating of marine fault scarps

Cores from the flanks of the Galapagos spreading centre show that the top 25 cm of pelagic sediments is highly bioturbated. Kenyon and Turcotte [1985] have proposed that bioturbation may cause down-slope creep of the sediment surface and bioturbation may therefore smooth sediment topography in a similar way to hillslope creep on land. Assuming this produces movement consistent with the diffusion transport model, sediment topography across scarp crests, digitised from Deep Tow profiler records, is modelled with a simple analytic solution to the diffusion equation and with a mean diffusion constant k of ∼0.007 m2/yr. This small value suggests creep rates are modest, for example, 2 cm/yr for a 30° slope, and is an upper bound since sediment avalanching and bottom currents probably also remove sediment from scarp crests. Although requiring further work, these results suggest that morphologic dating methods may be applicable to marine fault scarps and could be useful in relatively sediment-free areas, such as mid-ocean ridges, where it is commonly not possible to use datable offset seismic horizons.