I. general 



SYNOPSIS OF RESULTS 



In order to give the reader an over-all view of the findings 

 of this cruise into the Bering and Chukchi Seas, the following 

 synopsis is presented, necessarily in rather general terms. 

 For a more detailed discussion of the subjects mentioned, it 

 will be necessary to turn to the various sections of the report 

 itself, listed in the Table of Contents under the general di- 

 visions: Geological Observations, Physical Oceanographic 

 Observations, and Biological Observations. 



The sea floor of the Bering Sea is divided into two physi- 

 ographic provinces of approximately equal area by a pre- 

 cipitous continental slope which trends northwest-southeast. 

 Depth profiles obtained by echo sounders show that a deep 

 flat-bottomed basin with an average depth of about 2100 fa- 

 thoms occupies the region between the continental slope and 

 the Aleutian Islands arc. The northeastern portion of the 

 Bering Sea and the Chukchi Sea are shoal continental shelf 

 seas characterized by a remarkably smooth, flat, and feature- 

 less bottom; bottom gradients are typically less than one foot 

 per mile. Although these shelves were almost certainly ex- 

 posed to subaerial erosion during the lowered sea levels of 

 the Pleistocene, recent sedimentation has apparently masked 

 all physiographic features which were formed at that time so 

 that the shelves are now devoid of even minor topographic 

 irregularities. As it is unlikely that the profound erosive 

 features associated with continental glaciation could have 

 been masked by subsequent sedimentation, it appears that 

 even the most northerly portions of these shelves escaped 

 Pleistocene glaciation. 



The shelf sediments of the Bering and Chukchi Seas were 

 investigated by means of grab samplers, coring devices, and 

 underwater photos. From these data and from existing infor- 

 mation, a sediment chart was constructed showing the distri- 

 bution of sediments of various grade sizes. This chart shows 

 that uniform deposits exist over extensive areas. The sedi- 

 ments are largely clastic, consisting largely of sand, sand 

 with mud, mud with sand, and mud. In the Chukchi Sea, ice- 

 rafted detritus is quantitatively important. In addition to 

 grade size determinations, the diatom, foraminiferal, bac- 

 terial, and mineralogical content of the sediments were in- 

 vestigated. The sediments are similar to other high latitude 

 shelf sediments in that they have a low content of carbonate, 

 organic matter, and authigenic minerals. 



