Abstract 



Sediment core samples from the deeper areas (>200 meters) 

 of the Kara Sea, composed almost entirely of terrigenous elas- 

 tics, are predominantly silty clay which is very poorly sorted, 

 near-symmetrical to coarse-skewed and mesokurtic. The clay 

 minerals are kaolinite, chlorite, illite, an expandable component 

 which is probably montmorillonite, and possibly some mixed layer 

 clays. 



The upper layers in many cores display a color sequence from 

 the surface downward of light brown to dark brown to yellow- 

 brown to gray-green to brown to gray-green. No significant 

 textural or mineralogical difference exists between brown layers 

 and gray-green ones. In two cores non-detrital iron and man- 

 ganese are greatly enriched in the brown surface layers but 

 not at the same stratigraphic level. The highest concentration 

 of non-detrital manganese occurs several centimeters nearer 

 to the sediment-water interface than does the highest concen- 

 tration of non-detrital iron. Beneath the surface layers the 

 concentration of both elements is greatly reduced except in 

 the secondary brown layers which are somewhat enriched in 

 non-detrital iron and very slightly in non-detrital manganese. 



Non-detrital material isolated from the upper manganese- 

 and iron-enriched layers gave no diagnostic X-ray diffraction 

 patterns and is probably amorphous or crypto-crystalline. Co- 

 prolitic material from one secondary brown layer was identi- 

 fied as the iron phosphate, vivianite. 



The concentration of non-detrital iron in 98 surface samples 

 generally increases toward the mouths of the Siberian rivers, 

 suggesting that these are the sources of iron in the Kara Sea. 

 The distribution of non-detrital manganese in surface sediments 

 apparently is controlled by factors other than distance from 

 source. The non-detrital Mn/Fe ratio generally increases away 

 from the river mouths, suggesting that iron is deposited nearer 

 the points of influx than manganese. 



The distribution of non-detrital iron and manganese with 

 depth in the cores appears to the controlled by post-depositional 

 processes, including dissolution, migration, and subsequent dif- 

 ferential oxidation of iron and manganese ions, rather than by 

 primary depositional processes or variability in the rate of 

 influx. 



