the eastern side of the depression. In the west- 

 ern part of this transect, a southerly flow of 

 less turbid water is indicated. The current and 

 turbidity data suggest a net northward trans- 

 port of fine-grained sediment from the Bering 

 Sea toward the Arctic Ocean, with minimal 

 deposition in the eastern central Chukchi Sea. 



The sediment distribution pattern partly re- 

 flects the observed currents and water tur- 

 bidity. Mud present along the eastern flank of 

 the depression corresponds to the zone where 

 the bottom turbid layer is thickest (figs. 5 and 

 11). To the west and east, possible relict or 

 residual sand and gravel are present. Ice raft- 

 ing appears to be only a minor source of sedi- 

 ment, and probably accounts for most of the 

 rounded pebbles interspersed in the muds and 

 sands oflfshore. 



Geochemistry 



Geochemical analyses of seven sediment 

 samples from four locations in the Chukchi Sea 

 (table III, appendix A) indicate a reducing 

 sedimentary environment, except for the up- 

 permost 1 or 2 cm. This conclusion is based on 

 sediment color and the distribution of sulfur 

 and organic components. The alkaline-soluble 

 organic fraction was dominantly of the humic 

 type and averaged about 0.5 percent of the total 

 sediment, whereas the total organic content 

 averaged 1.7 percent of the dry-sediment 

 weight. The humic fraction, derived primarily 

 from land plant detritus, indicates a terrestrial 

 relict origin for the sediment, or a situation in 

 which the contribution of terrestrial detritus 

 masks the production of marine organic 

 matter. 



The bitumen (petroleum-like substances) 

 content was relatively low, averaging only 

 0.005 percent. Analyses revealed a constancy 

 of elemental abundances, with no abnormally 

 high values for either the total sediment or the 

 alkaline-soluble humic fraction (table III, ap- 

 pendix A). Although coal was present in the 

 coarse fraction of several samples, it ap- 

 parently was not a major organic constituent. 



Mercury values averaged less than 0.02 

 ppm and ranged from below the limit of de- 

 tection (0.01 ppm) to a maximum of 0.04 

 ppm (table II, appendix A). These are ex- 

 ceptionally low compared with concentrations 

 in oceanic sediments elsewhere. In some areas. 



for example, average values range from 0.05 

 to 1.20 ppm (Fleischer, 1970). However, they 

 are not unexpected, as there are no source areas 

 of mercury nearby, and the organic content of 

 the sediments is also relatively low. 



Copper, lead, and zinc values also were low 

 (table 1 and table II, appendix A), compared 

 with marine sediments elsewhere (Turekian 

 and Wedepohl, 1961). Arsenic values, however, 

 averaged 24 ppm (table 1 and table II, ap- 

 pendix A) — high compared with normal values 

 of 1-20 ppm (Wedepohl, 1969). 



Table 1. — Selected elemental concentrations in sediment 

 samples collected on 65 stations. (Analysis by Kam 

 Leong, U.S. Geological Survey.) 



CONCLUSIONS 



1. The movement of fine-grained particulate 

 matter involves transport toward the north 

 along the eastern side of the trough bisecting 

 the study area. Materials are transported from 

 south of Cape Lisburno and from the coastal 

 bight northeast of Cape Lisburne. Over shal- 

 lower parts of the coastal zone an anticyclonic 

 eddy and storms circulate and mix nearshore 

 waters. 



2. Beach processes were dominated by the 

 formation of numerous ice-gravel ridges. These 

 terrace-like ridges seem best explained by re- 

 peated changes of sea level due to storm surge 

 and by concurrent freezing of shore-fast ice. 



3. Gravel, gravel-mud, and gravel-sand 

 found in much of this region reflect the fact 

 that little or no sedimentation is going on. 

 Along the eastern parts of the central trough, 

 the presence of silty muds suggests sedimenta- 

 tion from the northward-flowing turbid layer. 

 The lack of gravel in this area indicates that 

 ice rafting is apparently not an important 

 mode of sediment deposition. 



4. Internal sediment structures caused by 

 extensive bioturbation reveal that the sedi- 

 ments are heavily utilized by benthic fauna. 



90 



