The morphology and sedimentology of landforms created by subglacial megafloods

Characterization of a glacial paleo-outburst flood using high-resolution 3-D seismic data: Bjørnelva River Valley, SW Barents Sea

“…Subglacial meltwater channels in Antarctica are further documented to both deepen and becoming increasingly focused in the downstream segment (Anderson and Fretwell, 2008; Simkins and others, 2017). Subglacial landforms generated by meltwater flows have expressions different from those identified in the Bjørnelva River Valley (Munro-Stasiuk and others, 2009). Whereas submarine channels can erode several tens of meters along the slope (e.g.…”

Bedrock mega-grooves in glaciated terrain: A review

“…While there is unanimous agreement that bedrock mega-grooves in glaciated terrain are landforms of subglacial erosion, there is disagreement regarding the agent of erosion. The predominant and traditional idea relates the formation of mega-grooves to direct glacial erosion by ice (Chamberlin, 1888;Carney, 1910;Smith, 1948;Zumberge, 1955;Goldthwait, 1979;Wardlaw, 1969;Boulton, 1974;Witkind, 1978;Lucchitta, 1981;Lowe and Anderson, 2003;Roberts et al, 2010;Krabbendam and Bradwell, 2011;Eyles, 2012;Krabbendam et al, 2016), whereas a more recent and entirely different interpretation claims that erosion of bedrock grooves of various sizes was carried out mainly, if not entirely, by subglacial meltwater (Baker and Milton, 1974;Sharpe and Shaw, 1989;Kor et al, 1991;Tinkler and Stenson, 1992;Shaw, 2002;Bradwell, 2005;Munro-Stasiuk et al, 2005;Munro-Stasiuk et al, 2009).…”

“…Several authors have regarded the large-scale bedrock grooves in Ontario, Canada, as the product of erosion by meltwater released catastrophically in high volumes during subglacial mega-floods (Sharpe and Shaw, 1989;Shaw and Gilbert, 1989;Kor et al, 1991;Tinkler and Stenson, 1992;Shaw, 2002;Munro-Stasiuk et al, 2005;Munro-Stasiuk et al, 2009). The grooves occur in the metamorphic rocks along the south-western margin of the Canadian Shield, as well as in Palaeozoic carbonate bedrock, which borders the shield along its southwestern margin.…”

“…In the absence of any indication of geological control, we share the view of others (Chamberlin, 1888;Carney, 1910;Smith, 1948;Witkind, 1978;Bradwell et al, 2008;Eyles, 2012) that the main process in the initiation of mega-grooves, was that of abrasion by glacier ice, given their straightness over the landscape and typical U-shaped cross-profile ( Figures 6A, 8 A and B, 10 A and B) (see section 4.1.1). It is unlikely that straight and parallel grooves of this size could have been initiated in bedrock by fast-flowing water vortexes as implied by the proponents of catastrophic subglacial mega-floods (Sharpe and Shaw, 1989;Shaw and Gilbert, 1989;Kor et al, 1991;Tinkler and Stenson, 1992;Shaw, 2002;Munro-Stasiuk et al, 2009; see also section 4.2). While water vortexes have the ability to erode channels in bedrock (Whipple et al, 2011), they would have had to advance in straight and parallel lines, over long distances and wide areas, in order to erode parallel grooves.…”

“…This, together with their parallel conformity and straightness over long distances, has prompted most geomorphologists to propose a subglacial origin for these landforms, traditionally related to quarrying and abrasion (Carney, 1910;Smith, 1948;Zumberge, 1955;Wardlaw, 1969;Witkind, 1978;Goldthwait, 1979;Lowe and Anderson, 2003;Roberts et al, 2010;Krabbendam and Bradwell, 2011;Eyles, 2012;Krabbendam et al, 2016). An alternative school of thought invokes the erosive action of meltwater rather than glacier ice, both on Earth (Baker and Milton, 1974;Tinkler and Stenson, 1992;Shaw, 2002;Bradwell, 2005, Munro-Stasiuk et al, 2009 and Mars (Baker and Milton, 1974). The lack of consensus with respect to the origin of bedrock mega-grooves exists not only between these two schools of thought, (i.e.…”