Table 2. -Trace element concentrations of selected sur- 

 face samples, 1971 



Mercury 



Size 

 fraction 



Total 



Number of 

 samples 



Average 

 (Ppb) 



170 



40.0 



Arsenic 



Range (ppb) 



10-250 



(Wedepohl, 1969) and just slightly higher than 

 those in the eastern Chukchi Sea (Barnes and 

 Leong, 1971; Barnes, 1972). Consequently, the 

 values reported here would appear to be back- 

 ground concentrations for these elements in the 

 region studied. 



Preliminary examination of the data suggests 

 that the concentrations are related to sediment 

 textures with higher values in finer grained sedi- 

 ments. However, the lack of baseline studies at 

 this time continues to make for a formidable prob- 

 lem of integrating source, transport mechanism, 

 and depositional regime at this stage of our know- 

 ledge. 



(ppm) 



(ppm) 



DISCUSSION 



Total 



Total 



Total 



Total 



170 



19.0 



Lead 



170 



12.4 



Zinc 



170 



87.3 



Copper 



170 



19.1 



6-60 



3-24 



20-180 



5-40 



production of marine organic matter (bitumen) 

 (Vernon Swanson. written commun.) 



Average concentrations of several heavy met- 

 als (table 2 and Appendix A) are close to those 

 found in oceanic sediments elsewhere 



Sedimentary Processes 



Carsola (1954) describes the northern shelf of 

 Alaska as one of coarser and more poorly sorted 

 sediments, compared with the shelf to the east, off 

 the Mackenzie River, and to the west, in the 

 northern Chukchi Sea. In these two areas, fine 

 sediments are derived from the Mackenzie River 

 and the Bering Sea, respectively. The absence of 

 these sources for the Alaskan Beaufort shelf left a 

 (relict?) coarser sediment. Carsola found the 

 dominant sediment to be a coarser silt, except for 

 finer materials off the Colville River. He believed 

 ice-rafting to be an important influence on the 

 textural parameters of the sediment. 



Naidu (1973 and this volume) notes an appar- 

 ent lack of gravel in the marine deltaic and 

 lagoonal sediments. He ascribes this dearth to 

 one of three possibilities: 1) lack of transport by 

 ice or currents, 2) dilution of gravel input by 

 sand, silt and clay deposition, and 3) insufficient 

 sample size. Our observations show that gravel is 

 not transported by ice or currents (Barnes and 

 Reimnitz. 1972). It is most probable that the 

 inshore area is a depositional area for sands and 

 mud. In contrast to the delta fronts and lagoons, 

 Naidu finds, as does this report, that the sedi- 

 ments further offshore contain a larger proportion 

 of gravel. He reviews: (a) the lack of evidence for 

 present-day transport, (b) the lack of a coarse to 

 fine sediment gradation offshore across the shelf, 

 and (c) the absence of modern hydrodynamic 

 conditions to transport gravel, and concludes that 



190 



