Abstract

Sub-Antarctic intertidal boulder pavements are located in three environments spanning 10 degrees of latitude. Some pavements are ice-pushed or ice-rafted boulders which have been forced into the substrate by the pressure of grounding ice blocks. Others result from wave-winnowing of glacial till at sea level which has been subsequently modified by grounding ice. Shallow depressions in the pavement surface may be the loci of large grounded ice blocks. This interpretation is supported by striation and boulder orientations on the ridges between the depressions. Occurrence depends on: a boulder supply, frequent onshore movement of floating ice, and a low-gradient intertidal zone. The degree of development of the pavement seems to be controlled by the frequency of onshore ice movement. Raised pavements in the South Shetland Islands suggest little morphogenetic change has occurred in the area since 9,000 years ago. Where the frequency of ice grounding is relatively low, periods in excess of 200 years are necessary for pavement development. Where the ice-grounding frequency is high, pavements are well formed within 300 years.--Modified journal abstract.

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