IV. DISCUSSION 



The geomorphology of the submarine topographic features of the eastern Ross 

 Sea and Sulzberger Bay is discussed here in the light of the probable glacial 

 history of the area . All of the categories of bathymetric features found on the 

 continental shelf of the Sulzberger Bay area are also found on other continental 

 shelves off glaciated regions of both hemispheres (Holtedahl, 1958; Shepard, 1948; 

 Zhivago, 1962). Explanations proposed for their origins should therefore be gen- 

 erally applicable (rather than unique) as far as factual data permit. 



A. Outer Shelf 



Soundings on H . O . charts nos. 6636 through 6646 (U.S. Navy, 1960-61) 

 show that the outer edge of the continental shelf lies at 200 to 300 fathoms or 

 more around the entire continent, except where it is transected by other features . 



Surf-base erosion during eustatic sea level drops associated with Pleistocene 

 glacial advances could not alone have caused this great shelf depth . The lowest 

 glacial sea level was less than 100 fathoms below the present sea level (Fairbrldge, 

 1961; Donn, Farrand, and Ewing, 1962). Thus, the low sea levels of Pleistocene 

 glacial maxima stood at less than one-half of the depth needed for surf-base 

 planatlon of the outer shelf to Its present depth . 



1 . Eustatic, Isostatic, and Glacial History . According to Nichols (1960), 

 no substantial evidence of Tertiary glaciation of Antarctica has been discovered . 

 The reconstruction of the probable glacial history of the continental shelf will, 

 therefore, open with some remarks on Pliocene sea levels. 



Fairbrldge (1961, figure 5, p. 119) shows Pliocene sea levels ranging from 

 10 to 100 fathoms above the present sea level . Additionally, Dietz and Menard 

 (1951) cite bathymetric evidence to show that wave-base planation Is non-existent 

 and that shelf planation is caused by surf action at shallow depths of less than 5 

 fathoms . 



From this, the Pliocene shelf break in Antarctica is assumed, by this writer, 

 to have been near what Is now sea level, I .e ., 200 to 300 fathoms shallower than 

 the present shelf break. 



According to Hollin (1962), the Antarctic ice sheet probably existed through- 

 out the Pleistocene and the regime of the ice sheet has remained highly positive 

 (98 percent of the accumulation on the grounded Ice sheet reaches the sea and 

 remains to be consumed by It directly from coastal ice cliffs or indirectly from 

 floating Ice shelves) . Because of this, the area of the ice sheet Is determined 



15 



