along the shelf ice face. This core was one of two taken on the 

 cruise which showed significantly greater amounts of organic carbon 

 at the bottom of the core than at tho topj the bottom percentage of 

 this core was 0,37 percent, 



3. Cape Colbeck to Bransfield Strait 



The area from Cape Colbeck through the Amundsen and Bellingshausen 

 Seas is not well known from the standpoint of bottom sediments. The 

 continental shelf and slope to the 3j500 meter depth line varies from 

 50 to 275 miles in width. The few cores taken in this area by the 

 ATKA were mainly on the shelf and in deeper water. 



Two cores were taken off Cape Colbeck at distances of 3 and 60 

 miles in water which was 175 and 800 meters deep, respectively. The 

 cores were 6 inches and 30 inches in length, and the color of the 

 sediment was medium gray in the nearshore sanple and dark greenish 

 gray in the deeper core. Penetration was alinost zero in the shallower 

 core and excellent in the deeper. The latter core was the longest core 

 obtained on the cruise. In the sand sized particles of the two cores 

 sphericity varied from low to high; roxmdness varied from angular to 

 subrounded in the nearshore core and was subrounded at the bottom of 

 the deeper core. Surface texture of the particles was rough polished, 

 dull, and smooth. In the core taken 3 miles off Cape Colbeck, the 

 sediment was marine glacial till. In the core obtained 60 miles off 

 tho cape, in 800 meters of water, the sediment type was a rock flour. 



Particles of sand size or ]T"ger made up 88 percent of the shallower 

 sample and 5 percent of the deeper sample. Clay size particles made up 

 about 3 percent of the shallow core and 52 percent of the deeper core. 

 The dominant mineral 'in the deep core was quartz with feldspar secondary, 

 Slat-c, schist, and graywacke were present in the top and slate, schist, 

 volcanics, and graywacke in the bottom of the deep coi-e. Quartz also 

 was the dominant mineral in the shallow core with feldspar secondary 

 except for rock fragments fotuid at the bottom of the core. The rock 

 fragments were composed of quartzite, slate, granite, granitoid rocks, 

 schist, gneiss, sandstone, and graywacke. The only organic remains 

 found in the cores consisted of some chitin at the top and diatoms at 

 the bottom of the shallow core, and some arenaceous foraminlfera at the 

 top of the deep core. The sorting coefficient for the shallower core 

 was 2,69 at the top and U,80 at the bottora, sket-mess in <^ units was 

 -0,03 and -0,ii5j and median diameters in ^ units were 1,05 and 0,38, 

 respectively. The organic carbon content was very low in the shallow 

 core (0.12 percent at the top and 0,02 percent at the bottom), possibly 

 because of the large percentage of sand sized particles. The organic 

 carbon content in the deeper core averaged 0,37 percent. 



50 



