Glacial erosion of continental margins (on the origin of fjords and submarine valleys of the glaciated shelves)

Abstract

All fjords and trough-shaped submarine valleys occur within the glaciated coastal mountains and adjacent glaciated shelves being completely absent in other coast and shelf areas. This distribution strongly suggests that the landforms are of glacial origin, and their hollows can be used for assessing the rate of glacial scour. The total volume of hollows in the eastern North Atlantic measures about 750,000 km³, or 280*10¹³ t, which is equivalent to removal of a 240-meter-thick rock layer. As for the distribution of the produced debris, 30% of their mass has been spent on late-glacial refilling of the hollows, 63 to 65% dumped on continental slopes and rises, about 1% deposited within the polar abyssal plain of the ocean, and 4 to 5% ice-rafted to its subpolar areas. Rate of scour in fjords and glacial submarine valleys turns out to have been ranging from 2.7 to 6.0 mm/yr which is an order of magnitude higher than rate of erosion by terrestrial glaciers, Data on glaciomarine accumulation in the western North Atlantic and in deep-sea trenches off south-west Alaska and southern Chile tally with these figures.