RECENT SEDIMENTATION AND ORGANIC-CARBON BURIAL IN A SHELF SEA - THE NORTH-SEA

To obtain a carbon budget of the North Sea, recent sedimentation rates and organic carbon and nitrogen concentrations were determined on 27 box cores from the shallow North Sea (with a water depth <200 m and a surface area of 500 x 10(3) km(2)). The sedimentation rates in these b ox cores range from 5 to 35 cm.100 year(-1), C-org concentrations are <0.05-1%. Based on these numbers and published data the total amount o f C-org buried in the shallow North Sea is calculated as similar to 1 x 10(5) tons.year (-1). In large parts of the shallow North Sea recent sedimentation is (nearly) absent. Reworking of relict deposits and pa rtial mixing of these deposits with small amounts of recent fine grain ed sediments by biological and physical processes and human activities (beam trawl fishery) result in apparent sedimentation rates which are likely to exceed the real net sedimentation rates considerably. The r esults of this study suggest that the majority of the organic matter i s exported from the shelf over the shelf edge into the Norwegian Sea a nd into inner shelf deeps (Skagerrak and Norwegian Channel). Coarse gr ained shelf sediments are only of minor significance for the preservat ion of organic matter. (C) 1997 Elsevier Science B.V.