The steep surface of the Ice moving down the sides of Edward VII Peninsula 

 and the abrupt change of slope where the Ice becomes afloat In Sulzberger Boy 

 may Indicate that this ice Is "dry, " i .e ., frozen to bedrock where aground . 

 Another indication of the possible dry-base nature of the Sulzberger Bay shelf Ice 

 Is the presence of dome-shaped ice-mounds (shown as small islands In Figure 2) 

 which may represent banks that the sub-freezing shelf Ice touched and froze to. 

 The ice then piled up from lateral pressure and prolonged accumulation of snow. 

 These mounds are mapped as Islands because their ability to remain stable against 

 the pressure of the surrounding shelf ice has indicated that they are more than tem- 

 porarily grounded icebergs. Byrd (1933) first reported these "Islands" in their same 

 positions more than 30 years ago. The front of the enclosing ice shelf has ad- 

 vanced at a rate of many miles per year, shedding icebergs to maintain more or 

 less the same frontal line. Robin (1953) shows similar relationships between the 

 grounded and floating "dry" Ice and its underlying topography and bathymetry in 

 the vicinity of Penchsokkia GIpcIer . 



Partially on the basis of studies of ancient tillltes, Carey and Ahmad (1961) 

 suggest that wet- and dry-base "glaciers" produce distinct sediment types, as 

 summarized in the following paragraphs. 



Wet-base Ice produces great thicknesses of unfossiliferous tills that may have 

 occasional sand or mud Interbedded and, in particular fades, strongly dragged or 

 rolled structures . These abruptly give place seaward to very different sediments - 

 marine sands and silts with rare dropped erratics Interbedded with frequent layers 

 of till-like turbidity deposits a few inches to several feet thick. The sediments 

 formed directly below the floating portion of the Ice shelf, but beyond Its basol 

 moraine, must be turbidites (formed from basal melt water and the steep gradient 

 of till) - unweathered, finely-ground rocks of sand to clay grade. By the time 

 the wet-base Ice reaches the Ice barrier edge, little sediment may be left in the 

 Ice. Crary, etal . (1962) and Zumberge and Swithinbank (1962) note that, as 

 the Ross Ice Shelf makes its 200-mile journey seaward, melting of its bottom sur- 

 face and snow accumulation on its top surface eventually replace the original 

 debris-laden terrigenous ice with clean, practically sediment-free ice. 



Dry-base glaciers, on the other hand, produce little In the way of tills, but 

 yield marine muds with abundant erratics, all of which have been dropped through 

 water at that distance offshore where the floating portion of the glaciers warm to 

 melting temperature . The grounded zone of dry-base ice at the continental mar- 

 gin does not differ from dry-base ice of the continent. In that the full load of 

 the dry Ice laden with debris grinds (and compacts?) the pavement . There can 

 be little sedimentation. If any, in this zone. None of the till-flow and turbidity 

 current phenomena should be expected with dry-base glaciers (Carey and Ahmad, 

 1961). 



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