to a C/N ratio (at/at) of 7.7, slightly higher than the commonly 

 accepted "Redfield Ratio" of 6.6 for marine organic matter 

 (Froelich era/., 1979). Mostlikely,thisindicatesacontribution 

 of terrestrially derived organic matter to these sediments. 

 There is a possibility that recycling of sedimentary organic 

 matter could lead to a selective reduction in nitrogen content, 

 thus raising the C/N ratio. 



The distributions of C/N ratios in sediment tmes of the 

 study area are shown in Fig. 7. A strong influence of the 

 contribution of terrestrial organic matter is readily apparent at 

 the mouth of the Yukon River. This is the same relationship as 

 observed for the carbon isotopic composition distribution. 

 Thus, much of the organic matter in these sediments must be 

 derived from terrestrial sources transported to the Bering Sea 

 by the Yukon River. The relationship between the two 

 parameters is shown in Fig. 8. There is a complete overlap of 

 samples from the area of the mouth of the Yukon River and 

 Norton Sound with those from the rest of the study area. All of 

 the samples having 5"C<-24 per mil or C/N ratio >1 1 are from 

 the Yukon area. 



Figure 9 shows isopleths of a devised "environment of 

 deposition" parameter formed from the normalized (0.0 to 1 .0), 

 unweighted product of (5"C and the C/N ratio values used for 

 Figs. 3 and 7, respectively. Both of these parameters are 

 dependent, at least in part, on their terrestrial organic 

 contribution. Thus, their product would tend to emphasize this 



m 



Q 

 Q. 



-18 



-20 



-22 : 



-24 - 



-26 



-28 



13 



15 



17 



C/N Ratio 



Fig. 8. Relationship between carbon isotope values and C/N ratios for 

 sediments. 



Chukchi Sea 



Fig. 7. Areal distribution of C/N ratios in sediments. 



Fig. 9. Contours of a relative parameter of "environment of origin" of 

 sediment organic matter. 



337 



