Geochemical fractions and indicators of sedimentation conditions in the Barents sea

Research results of geochemical fractions and distribution pattern of the major and trace elements in the sediment cores of the Barents Sea are presented. In the sediment core AMK- 5193, located in the central part of the sea, Al, Cr and Ni were detected predominantly in the lithogenic form (75−97% of the total content) throughout the core. A large or a noticeable portion (from 65% to 30% from total contents) of Pb, Cd, Cu, Ni, Co, Mn, and As was found to be accumulated due to hydrogenous processes, such as adsorption on amorphous Fe-Mn oxyhydroxides and clay particles. In the uppermost oxidized layer (0−6 cm) of St. AMK-5193, where the most intensive exchange processes between the solid and liquid phases of bottom sediments happen, a significant increase in the proportion of geochemically mobile fraction of most metals was found. In this part of the core, the maximum content of Fe and Mn in the form of authigenic oxy-hydroxides which serve an effective sorbent of most trace elements, including heavy metals, was recorded. At st. 5194, the downcore rythmic covariation of the Si/Al, Ti/Al and Fe/Al ratios reflecting contribution of terrigenous matrix, as well as Al/Ca ratio (indicator of physical and chemical weathering) was revealed. Moreover, the Al/Ca ratio exhibited an asynchronous change with the Si/Al and Fe/Al ratios. Also, the downcore variation in the Ti/Al ratio was opposite to that of Mn/Fe (an indicator of geochemically mobile fraction). Variation of the Ti/Zr ratio, reflecting the range of aerosol transport of clastic material, is weakly expressed in the AMK-5194 core, which supports the proximity of the terrigenous source.