although a fair negative correlation can be dis- 

 cerned between these parameters when sedi- 

 ments of all environments are considered together 



Heavy Mineral Analysis 



There are no unusually high concentrations of 

 heavy minerals in any of the sand sizes (Table 2). 

 In fact, the contents of heavy minerals are quite 

 low. Relatively higher percentages of heavy min- 

 erals are generally observed in progressively finer 

 size fractions of any one sand sample. 



Clay Mineral Analysis 



The weighted peak area percents (after Bis- 

 caye, 1965) of clay minerals in the <2)U, e.s.d. 

 size of the deltaic sediments of north arctic 

 Alaska are presented, together with ratios of these 

 percents, in Table 3. The percentages are classed 

 according to depositional environments. Some 

 lateral variations in clay mineral assemblages 

 and ratios are apparent. In fact, a line of demarca- 

 tion between two clay mineral facies can be drawn 

 somewhat arbitrarily from Oliktok Point and ex- 

 tending northward perpendicular to the coast 

 (Figure 1). To the west of this line sediments are 

 relatively richer in smectite and kaolinite, 

 whereas east of the line relatively higher amounts 

 of illite are encountered. This fact is well exem- 

 plified by the presence of higher illite/smectite 

 and illite/kaolinite ratios east of Oliktok Point 

 (Table 3). No progressive downstream changes 

 have been observed in clay mineral assemblages 

 in the <2^t e.s.d. size over the last 161-km 

 length of the Colville River (Figure 6). The clay 

 mineral assemblages of samples CR4 and CR5 

 are unusually rich in smectite. It may be noted 

 that at the points where these two samples were 

 collected (Figure 1 and 2) two tributaries — 

 Ingaluat Creek and Kogosukruk River 

 respectively — flow into the Colville River. Sam- 

 ple 8, which was collected at the point of conflu- 

 ence of the Itkillik River tributary with the Col- 

 ville River (Figure 1 and 2), has a great paucity of 

 smectite and notably higher chlorite and kaolinite 

 (Table 3). Typical X-ray diffraction traces of 

 non-glycolated, <2/A e.s.d. sizes of Colville 

 River clays, and to a lesser degree the nearshore 

 deltaic clays as well, show a broad shoulder on 



the low angle side of the illite peak (Naidu, 1974). 

 The presence of this shoulder suggests that the 

 illite in these samples is associated with some , 

 other clay mineral components as mixed-layer 

 phases. Our detailed clay mineral studies indi- 

 cate the presence of mixed-layered illitic materi- 

 als with associated interlayers of chlorite and/or 

 smectite components, as well as the possible oc- 

 currence of degraded illite and/or chlorite in 

 these sediments. 



Chemical Analysis 



Results of chemical analysis of the deltaic sed- 

 iments of north arctic Alaska are presented in 

 Table 4. For the purpose of comparison, the aver- 

 age elemental abundances of the deltaic sedi- 

 ments and those of the nondeltaic shelf and ex- 

 trashelf of the Beaufort Sea (after Naidu and 

 Hood, 1972) are included in Table 5. 



Organic carbon contents in the deltaic sedi- 

 ments of north arctic Alaska are significantly 

 lower than those observed in tropical deltaic sed- 

 iments (Trask, 1939; Naidu, 1966). It is observed 

 that there is a progressive seaward increase in 

 organic carbon and a decrease in carbonate con- 

 tents of sediments from the delta to the extrashelf 

 through the shelf (Table 5). If fact, there is a great 

 enrichment of carbonate and Ca in the deltaic 

 sediments under study. 



When compared to sediments of the marine 

 facies of tropical deltas (Clarke and Washington, 

 1924; Hirst, 1962a, 1962b; and Naidu, 1968), 

 the concentrations of Fe, Mn, and K are signifi- 

 cantly lower and those of Ca, Mg, Na, Co, and Cu 

 are higher in the deltaic sediments of north arctic 

 Alaska (Table 5). However, in the far offshore 

 nondeltaic shelf and extrashelf sediments the rel- 

 ative concentrations of all elements except Ca 

 and Co are significantly higher than those ob- 

 served in the north arctic Alaskan deltas (Table 



5). 



Within the delta, the order of average carbo- 

 nate abundance in the various environments is as 

 follows: lagoon (12.06%) >open marine (7.48%) 

 > Harrison Bay (4.12%). On an average the 

 contents of organic carbon are similar in the Bay 

 (0.77%) and lagoon (0.79%) sediments, but sed- 

 iments of the open marine deltaic facies have 

 relatively lower organic carbon (0.58%). 



244 



