sea water must approach the freezing point before the surface 

 freezes. 



Little is known of the character of the continental slope 

 in the Chukchi Sea. However, because of the oceanographic 

 factors involved, one can predict that its geographic position 

 coincides closely with the limits of the permanent polar ice- 

 pack. 



Transport of Sediment by Currents. Although bottom 

 currents in the Bering Sea and especially in the Chukchi Sea 

 are presumably weak, the grade size and sorting of the bottom 

 sediments show that current action has effectively sorted and 

 transported large amounts of bottom material. The Bering 

 Sea is largely covered by fine sand, indicating that the silt 

 and clay carried in from shore must bypass the shelf. Judging 

 from the surface currents, it is likely that the silt and clay, 

 when carried out to the open shelf, are largely transported 

 to the north into the Chukchi Sea. The quieter water of the 

 Chukchi Sea permits the settling out of finer material, but 

 even there the sediments are low in clay and diatom frustules, 

 showing that the finest sediment must also bypass this shelf 

 and move into the arctic basin. 



The sediment-laden and turbid bottom water layer de- 

 tected by photography is direct evidence of detritus being 

 transported in suspension. It was not possible to determine 

 if this turbid layer assumes the properties of a suspension 

 current, but the general absence of an appreciable grade for 

 such a current to move down makes this unlikely. It is proba- 

 ble that the suspended material is carried along by the north- 

 setting, semipermanent currents. 



Most of the samples, when fresh, had a watery layer of 

 brownish (oxidized) sediment about 1 to 3 inches thick at the 

 top resting on a stiffer and darker (reduced) substratum. It 

 is possible that this water layer is material which goes into 

 suspension under conditions of maximum bottom agitation and 

 that it is thus being actively transported. 



