beaches (Naidu et al, 1970) show that barrier 

 beach sediments from the polar regions have 

 distinctly different size distributions from 

 similar sediments of the low-latitude regions. 

 The difference is in the very poor sorting and 

 the predominance of gravels in polar beach 

 sediments. The gravel-size coal pieces in the 

 Point Lay barrier beach sediments possibly 

 have their source in the coal deposits which 

 outcrop in the adjacent coastal region. 



The analyses of the sediment samples com- 

 pleted so far suggest that the chief source of 

 chlorite in the eastern central Chukchi Sea is 

 the adjacent hinterland and that this source 

 probably does not contribute any significant 

 amounts of smectite. Presumably, smectite is 

 transported to the eastern central Chukchi Sea 

 through the Bering Strait, from the Chirikov 

 Basin. Presence of smectite in this basin has 

 been reported by Moll (1970) and the currents 

 necessary to transport it northward are also 

 known to be present (Aagaard and Coachman, 

 1964). The contrast observed in the relative 

 abundances of clay minerals in sediments from 

 the eastern central Chukchi Sea and Beaufort 

 Sea suggests: (1) a difference in the nature of 

 source material for the sediments of the two 

 seas and/or (2) a difference in physico-chem- 

 ical processes in the two seas which help to 

 sort out two different assemblages of clay 

 minerals from the same source material. Bis- 

 caye (1965) and Griffin et al. (1968) have cited 

 latitudinal variations in clay mineral as- 

 semblages. The thesis presented by the above 

 authors is supported by results of the study on 

 the Chukchi Sea sediments. However, data 

 from the Beaufort Sea (Naidu et al., 1971) do 

 not run parallel to the trend of clay mineral 

 distributions suggested by Griffin et al. (1968). 



The analysis of the pore waters of marine 

 sediments has increasingly become an integral 

 and important part of geochemical investiga- 

 tions. These studies have shed some light on 

 the understanding of the origin of brines and 

 early diagenesis. Some interesting patterns of 

 distribution of various ions are evident from 

 figures 8 and 9. Although the concentration of 

 Na* in interstitial water generally increases 

 with depth, at a certain horizon in some cores 

 a minimum is noted. This minimum generally 

 coincides with increased clay content in sedi- 

 ments. It appears that the concentration of 



Na* in interstitial water is primarily controlled 

 by the amount of clay present in sediments. 

 Similar observations were made in southeast- 

 ern Alaska (Sharma, 1970a, 1970b and 1970c). 

 These variations in Na+ concentrations are re- 

 lated to ion exchanges between Na* in in- 

 terstitial water and clay particles. 



The observed increase of K^ with depth in 

 the interstitial waters is believed to be due to 

 dissolution of feldspars as suggested by Garrels 

 and Howard (1959). Similar increase of K+ in 

 interstitial waters has been reported by Siever 

 et al. (1961, 1965) and Friedman et al. (1968). 



Decrease in Mg** with depth in interstitial 

 waters has been reported by various authors; 

 however, the explanations offered for such a 

 decrease differ. Some investigators believe that 

 Mg** from interstitial waters is increasingly 

 fixed by clay preferentially over K+ with in- 

 creased depth which is contrary to the con- 

 clusion of others who believe in the formation 

 of dolomite. Dolomitization results in simulta- 

 neous decrease in magnesium and calcium ions. 

 Recently Drever (1971) proposed that Mg^ 

 from interstitial water replaces Fe*+ in the 

 clay mineral structure. He suggested that re- 

 moval of Mg** from seawater controls the com- 

 positions of interstitial waters in sediments. In 

 view of simultaneous decrease of Mg^ and 

 Ca+* in the samples we have analyzed we are 

 inclined to conclude that such a decrease is due 

 to the formation of dolomite mineral. This con- 

 clusion has to be confirmed by the detection of 

 dolomite which has originated in place, a task 

 that is difficult to accomplish. 



The variational trends of Mn** indicate a net 

 upward migration of it by a mechanism similar 

 to that suggested by Bonatti et al. (1971) . Such 

 upward migration and enrichment generally 

 occurs because of the presence of a reducing 

 environment in the bottom sediment layers. 

 The distinct darker color and release of H2S 

 from the lower portion of core sediments of the 

 eastern central Chukchi Sea suggest reducing 

 conditions in those sediments at depth. Iron 

 concentrations vary erratically and explanation 

 for this behavior is difficult on the basis of 

 available data. Mn/Fe ratios were considered 

 in an attempt to explain the distribution of 

 iron in the interstitial waters; however, 

 measurements of several other parameters are 

 needed to forward an adequate explanation. 



177 



