in an indentation in the Antarctic Continental Slope. Since its location 

 is beneath the Ross Ice Pack on the side opposite the indentation from 

 Cape McCormick, the nearest land about lUO miles vest, the supply of 

 coarse terrestrial sediment, except for occasional dumping from icebergs, 

 should be relatively lov. This dumping shows up in the 18- to 20-inch 

 segment of the core where 6.1 percent of the sediment is sand size or 

 coarser and kO percent of this is composed of rock fragments. Except for 

 this segment, the silt-size fraction is remarkably high and constant at 

 approximately 50 percent of the sample. This is not typical of glacial 

 marine sediments. The content of radiolaria is adequately high for this 

 core to be classed as a radiolarian ooze, except for the higher percent- 

 age of sponge spicules. Because of its location, slumping from the 

 shelf could account for all or part of the sediments sampled. 



2. Thurston Peninsula Area 



a. BURTON ISLAND and GIACIER obtained thirteen bottom sediment 

 samples close inshore along the Thurston Peninsula for a distance of 

 over 90 miles from 101 e 57'W to 96°50'W. The bathymetry along this coast 

 is extremely irregular and the bottom sediments vary in texture and 

 composition. Two submarine rifts with depths in excess of 500 fathoms 

 were crossed along the coast. These are to the east and west of Novtlle 

 Peninsula. It is impossible to tell their extent to the north from the 

 available soundings, but oceanographic stations over them sampled warm 

 Antarctic Circumpolar Water at depth, which indicates they must be open 

 to the north. 



In texture, sediments range from silty sands on the shoals to pebbly 

 silty clays in the deeps. For the most part, they are gray to brown in 

 color, of medium low to medium high sphericity, subangular in roundness, 

 and dull-pitted to polished-pitted in surface texture. Feldspar is the 

 predominant mineralogical constituent while rock fragments are secondary. 

 Quartz, pyroxene, and mica also are important constituents. All grains 

 are fresh and unweathered. Very few radiolarians and diatoms are evident 

 in these sediments, but the Globigerina and benthic foraminifera content 

 total as high as 55 percent, especially where the bottom water tempera- 

 ture was found to be warmer than 0°C. In the few cores that are long 

 enough, and in which the biological content at the surface is prominent, 

 it appears that no appreciable organics, except for sponge spicules, 

 extend to a depth greater than 3 to k inches. 



b. Three cores were obtained by the ships north of Thurston 

 Peninsula but still on the shelf in depths of 300 fathoms or less. Two 

 of these cores in 225 and 235 fathoms consist primarily of feldspar and 

 rock fragments with relatively little biological constituents, except for 

 appreciable amounts of fecal pellets in GLACIER core lk. In texture, 

 these 2 cores average from silty mud to sandy mud, particularly in their 

 surface layers. GLACIER core 13 in 300- fathoms depth, however, ranges 

 from clayey silt to silty mud in texture and consists primarily of 



^9 



