The sediment types range mostly from olive gray to greenish black 

 silts and sands. Their mineral grains, for the most part, average 

 medium to medium high in sphericity; subangular to subrounded in round- 

 ness; and dull-pitted to polished-pitted in surface texture. Although 

 the bottom of McMurdo Sound appears to be very irregular, hard, and 

 variable in composition there seems to be a general decrease of mean 

 phi size and biological content vith increasing water depth. Charting 

 distribution of the biological constituents indicates there is possibly 

 an increase in the planktonic micro-organism content of the sediments 

 from west to east and from south to north. 



b. Southwestern Ross Sea - EASTWIND cores 14 and 15 were ob- 

 tained in slightly over 400 fathoms of water, one to the north and the 

 other to the south of Beaufort Island. Although only about 20 miles 

 apart, they differ materially in composition. The northern core (ih) 

 consists primarily of the remains of planktonic organisms throughout 

 its entire length, excluding the very bottom where volcanic glass and 

 feldspar become the predominant constituents. Core 15, however, is 

 predominantly feldspar, volcanic glass, and rock fragments throughout 

 its entire length. 



c. Southeastern Ross Sea - Five of the seven cores taken by 

 GIACIER in this area extend over a distance of more than 130 miles 

 along the Ross Ice Shelf. In these, the top comparatively rich organic 

 zone, varying from 5 to 7 inches thick, appears to indicate a period of 

 relatively high plankton productivity. Below this, the microfauna are 

 sparse but increase somewhat at the bottom of the two longest cores, 6 

 and 7* Volcanic glass and rock fragments are present in a l l of these 

 cores, but their occurrences are so variable and irregular, due probably 

 to glacial dumping, that they are useless for correlation. However, be- 

 cause of the high percentage of rock fragments in cores k and 5 and their 

 contained pink feldspars, which are uncommon in the other cores, these 

 sediments are probably derived from Roosevelt Island, immediately to the 

 south xinder the Ross Ice Shelf. 



Cores 1 and 2 taken by GLACIER somewhat farther north of the ice 

 shelf are similar to those described. The calcium carbonate content of 

 the silts from core 2 was analyzed. This decreases from a high of 3* 75$ 

 at the top to a minimum of 2.0$ at 9 to 12 inches depth and then in- 

 creases to 2.75$ at the bottom of the core. The data are not adequate 

 for correlation, but indicate a low calcium carbonate content for 

 Southern Ross Sea sediments. 



d. Northwestern Ross Sea - The only other bottom sediments ob- 

 tained in the Ross Sea were in the northwest sector in water depth exceed- 

 ing 1,000 fathoms. EASTOTND sample 2, containing a high percentage of 

 rock fragments and radiolarian tests, consists of surface mud taken from 

 the bottom Nansen bottle of an oceanographic cast. Core No. 3 was taken 



48 



