Highlights

Sediment gravity currents commonly are invoked as important processes controlling deposition of the deep-marine stratigraphic record.  Deposits of these currents, which commonly include the idealized Bouma succession, lack evidence of a dune cross-stratified unit that would be present were deposition merely the result of decelerating flow.  Where did they go?  Arnott suggests that this absence is the result of elevated concentrations of suspended sediment (high density), which in turn inhibits development of hydrodynamic instability that could lead to development of dunes.  This conceptual model explains why dunes, so prevalent in coarse-grained terrestrial and shallow marine deposits, are rare in the deep-marine record.

Turbidites and the case of the missing dunes by R.W.C. Arnott