recovery of f-he Antarctic continental shelf has lagged behind isostatic re- 

 bound in the Northern Hemisphere . The narrower zone of crustal ice-loading 

 and unloading in Antarctica has been depressed to greater extents over longer 

 intervals of time than have the broader zones of glaciated continental margins 

 in the Northern Hemisphere . Isostatic adjustment of the outer shelf of Sulz- 

 berger Bay may be considerably less than half completed at present. Geomor- 

 phic evidence of extensive former ice advance contrasts with evidence of a 

 comparatively small amount of rebound . 



b. Glacial compaction of Tertiary and interglacial marine sediments of the 

 outer shelf seems likely in view of the probability that the shelf surface bore 

 a great weight of ice . 



c . Glacial erosion of the shelf surface by grounded ice may have taken place . 



d. The rate of Pleistocene marine sedimentation of the continental shelf has 

 been slow because most of the ice-rafted sediment seems to have been deposit- 

 ed beyond the outer shelf. 



B. Shelf Depressions and Inner Shelf 



The deep, trough-like depressions found within the continental shelf surface 

 of the Sulzberger Bay area are not unique . Examination of H . O . charts 6636 

 (U.S. Navy 1960-61) shows deep transverse and longitudinal depressions in the 

 continental shelf surface along all sides of the Antarctic coast . Most of these 

 great troughs have a minimum relief of 100 fathoms and frequently reach depths 

 of 500 fathoms near the shore side of the shelf. These depressions often occur in 

 clusters of longitudinal depressions near shore together with transverse depressions 

 whose floors slope upward as they approach the outer edge of the shelf. These 

 clusters of depressions are bounded on their inner sides by steep-sided, relatively 

 shallow inner shelves across which they frequently extend to connect with existing 

 ice streams ("glaciers" on charts) . The outer sides of the depressions are bordered 

 by moraine-like mounds or ridges which often have reliefs of 100 fathoms above 

 the shelf surface. The transverse depressions usually transect these ridges at the 

 outer shelf, but appear not to cut through the shelf break at their seaward ends. 



Zhivago and Lisitzyn (1957) discuss the "inner shelf depressions" in the 

 Antarctic continental shelf adjacent to the Indian Ocean. Holtedahl (1958) and 

 Shepard (1948) have noted strikingly similar depressions and banks of the glaciated 

 coasts of the Northern Hemisphere . (The interested reader can compare Zhivago 

 and Lisitzyn's Figure 4 (1957), Holtedahl 's Figures 1 through 6 (1958), and Figures 

 2 through 5 of this paper) . 



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