Klenova (1938) suggested that iron and man- 

 ganese oxides were responsible for the brown 

 color in the upper layers of Kara Sea sedi- 

 ments and that the stability of these oxides, 

 and hence the color of the sediments, was de- 

 pendent on the amount of dissolved oxygen in 

 bottom and sediment interstitial waters and or- 

 ganic matter in the sediments. 



Brujevicz (1938a,6) and Trofimov (1939) 

 measured the redox potential (Eh) and pH 

 with depth in several Kara Sea cores. Trofimov 

 (1939) observed a transition from oxidizing to 

 reducing conditions on entering subsurface 

 gray-green layers and a corresponding sharp 

 decrease in the pH at the boundary between 

 oxidizing and reducing conditions (fig. 2). He 

 proposed that isolation of strata from oxygen- 

 ated bottom waters by burial and consumption 

 of oxygen in interstitial water by oxidation of 

 organic matter produced the redox potential 

 and PH profiles. The sharp decrease in pH at 

 the boundary between oxidizing and reducing 

 conditions was attributed to hindered removal 

 of the CO2 produced in the oxidation of or- 

 ganic matter. Brujevicz (1938a, 6) predicted a 

 separation of the more mobile phases of iron 

 and manganese in response to the gradient in 

 redox potential between buried strata and the 

 sediment-water interface. 



Klenova and Pakhomova (1940) observed an 

 increase in the content of manganese with de- 

 creasing grain size in Kara Sea sediments, 

 with clayey muds averaging 1.2 percent by 

 weight manganese. They also noted that the 

 highest content of manganese (3.5 percent) oc- 

 curred in dark brown (chocolate) sediments 

 and these occurred in regions where the salin- 

 ity gradient between surface and bottom water 

 was the greatest. 



Yermolayev (1948a,6) has characterized the 

 typical physical features of Recent Kara Sea 

 stratigraphy (table 1). He proposed that non- 

 uniform lithogenetic processes associated with 

 microorganisms and the hydrological regime 

 have operated to produce the physical and 

 chemical properties observed in Kara Sea 

 cores. The processes are nonuniform according 

 to Yermolayev because aerobic conditions pre- 

 vail in some layers (upper brown) and anaero- 

 bic conditions prevail in others (subsurface 

 gray-green) and because the hydrology of the 

 Kara Sea has undergone changes in the recent 



geologic past in response to periodic influx of 

 warm Atlantic waters at intermediate depths. 

 He observed a direct correlation between the 

 thickness of the warm intermediate Atlantic 

 water and the thickness of oxidized (brown) 

 bottom sediments in the Arctic seas and polar 

 basin and suggested that the secondary (bur- 

 ied) brown layers were generated during pe- 

 riods of maximum influx of Atlantic water. Ac- 

 cording to Yermolayev these periods would be 

 characterized by well ventilated bottom waters 

 in response to the increased surface and inter- 

 mediate circulation which would favor oxida- 

 tion and retention of ferromanganese com- 

 pounds in the sediments. The finding by Belov 

 and Lapina (1959) of increased amounts of 

 ferric and manganese oxides in Arctic basin 

 sediments deposited during periods of influx of 

 warm Atlantic waters into the Arctic Ocean 

 lends some support to Yermolayev's hypothe- 

 sis. 



The results of an experiment conducted by 

 Yermolayev (1948a,&) shed considerable light 

 on the nature of the stability of the secondary 

 brown layers and the reversibility of aerobic- 

 anaerobic processes. When a typical core (table 

 1) from the Kara Sea was inverted, i.e., placed 

 such that the brown layers (la, 16, Ic) were 

 sealed oflF from exchange with overlying 

 water and the gray-green layers exposed to 

 exchange with the overlying water, the brown 

 layers were transformed to gray-green layers 

 and the gray-green layers transformed to 

 brovni layers after a period of 17 months. The 

 exception to this was that the bright orange 

 layer (Ic) did not transform. This layer and 

 the lower brown layer (116) were designated 

 "zones of lithogenesis" by Yermolayev and 

 possessed the highest Fe'^*/Fe=+ ratio (20- 

 25). He demonstrated that bacteria were 

 largely responsible for this transformation by 

 repeating the experiment with sterilized sedi- 

 ment. In this case the transformation was con- 

 siderably retarded, if not halted completely. 

 He concluded that bacteria played a considera- 

 ble role, even if indirect, in determining the 

 physical characteristics of Kara Sea sediments. 



Gorshkova (1957) outlined in detail the tex- 

 tural, mineralogical and geochemical charac- 

 teristics of Kara Sea sediments both regionally 

 and with depth in cores. She also concluded 

 that the color of Kara Sea sediments depended 



