Wave-Emplaced Coarse Debris and Megaclasts in Ireland and Scotland: Boulder Transport in a High-Energy Littoral Environment: A Discussion

Abstract

Scheffers et al. (2009) describe a reconnaissance survey of boulder accumulations along parts of the Atlantic coasts of the British Isles. A substantial part of their report concerns the characteristics of wave-transported boulder deposits found high above sea level on cliffs. These boulder deposits reach perhaps their ultimate development along the coasts of the Aran Islands, Galway Bay, western Ireland, and Eshaness, Shetland, northern Scotland, where evidence of wave action reaches elevations of 50 m above sea level (a.s.l.). We have previously investigated in detail these and numerous other similar localities and concluded that the boulder deposits are cliff-top storm deposits (CTSDs), part of an assemblage of features found on certain cliffs on these very high-energy coasts that relate to the impacts of extreme waves during major storms (Williams and Hall 2004; Hall et al. 2006, 2008; Hansom et al. 2008; Hansom and Hall 2009). However, Scheffers et al. (2009, p. 571) claim that at these and other sites “no evidence ... exists for storm wave dislocation of ... boulders found at altitudes of 120 m a.s.l.” Indeed, “no calculations of possible storm wave heights, storm wave physics, or ages of the deposits and no descriptions of extraordinary storms are sufficient to explain these displacements” (p. 568), and “alternative explanations, such as tsunamis, should be considered” (p. 571). Here we rebut these claims by briefly restat-