Characteristics and formation of bedrock mega-grooves (BMGs) in glaciated terrain: 2 – conceptual models of BMG initiation

Abstract

Understanding BMG formation equates to being able to explain their initiation as well as their subsequent evolution. Several scenarios of bedrock mega-groove (BMG) initiation are proposed here, which attempt to explain how such parallel fluted terrain could be incised through resistant substrates over the relatively short temporal periods associated with uni-directional fast ice flow. In cases where geological controls have been inferred from the BMG morphology or location, groove initiation was likely either structural through the exploitation of linear features, or lithological, whereby the origin of harder erodents necessary for abrading softer rocks can be explained by the succession of adjacent lithologies along former ice flow paths. Where no geological control over BMG initiation could be inferred, it is hypothesized that their initiation was due to antecedent land surface conditions, through gradual bedrock elimination or related to pre-Quaternary regolith on etchplains, which was potentially a source of erodents no longer visible in the landscape.