Comment on “Large-scale bedforms along a tideless outer shelf setting in the western Mediterranean” by Lo Iacono et al. (2010) in Continental Shelf Research vol 30, pp. 1802–1813

Lo Iacono et al. (2010) report the discovery of large (but degraded) subaqueous dunes on the outer continental shelf NE of Valencia, western Mediterranean Sea. They argue that the dunes, after having been generated sometime in the past, are being episodically rejuvenated by high-energy flow events to the present day. Because the height vs. wavelength relation of the dunes falls below the global mean trend predicted by the equation of Flemming (1988), they claim to have discovered a new, low-amplitude type of flow-transverse bedform which typically occurs on microtidal current-swept outer continental shelves. A close inspection of the evidence shows that the reasoning of Lo Iacono et al. (2010) is flawed and that their interpretations and conclusions are premature and unjustified.

► The degraded dunes became moribund at the same time as the large sand bodies on which they occur. ► Only between 11 and 9 ka BP were current velocities high enough to generate subaqueous dunes. ► The discrepancy between observed and predicted dune heights is explained by long-term degradation. ► The postulation of a new type of low-amplitude dune occurring on microtidal shelves is unjustified.