Preservation potential of tsunami deposits on arid siliciclastic coasts

The Peruvian examples reviewed here show that the preservation of arid-coast tsunami deposits depends on interactions that are more complex that hitherto perceived. These involve sediment type, grain size, depositional setting, co-seismic movement, bioturbation, winds, and anthropogenic modification. In one example, all traces of the tsunami have been removed or reworked by flash floods and ocean waves. In another example, clasts on a coastal plain from tsunami-backwash began to be rounded and abraded by eolian sands immediately after the event. Eolian processes also smoothed and filled tsunami scours. By contrast, muddy tsunami deposits in certain areas escaped erosion by wind, probably because of their greater cohesion. In still another example, 0.5 m of co-seismic uplift was not enough to prevent ocean waves from removing a tsunami sand sheet that had mantled a coastal marsh. The buried record of tsunami deposits on modern coasts may therefore not fully represent the vulnerability of these regions to tsunamigenic hazards.