This thesis contains the results of the research on the burial of organic carbon in the North
Sea. Shelf seas, like the North Sea, are important areas of primary production and therefore
important possible sinks for Corg.
Calculations based on 210Pb and 137Cs sedimentation rates, and 3.5 kHz and Chirp penetrating
echo sounding data from the Norwegian Channel, Skagerrak and northern Kattegat (NE North
Sea), show that on a yearly basis 28x10^6 tons of sediments are deposited in the Norwegian
Channel and 46x10^6 tons per year in the Skagerrak and northern Kattegat. The Corg accumulation in these two areas is calculated as 0.83 and 0.17x10^6 tons per year respectively. Of this amount only 10% is accounted for by local primary production. The remainder is produced elsewhere in the North Sea or imported from the Atlantic Ocean, Norwegian Sea, Baltic Sea and terrigenous sources. Storm wave and -current induced bottom nepheloid layers are thought to be responsible for the transport of the fine grained sediments and the attached organic matter from the North Sea plateau into the Kattegat, Skagerrak and Norwegian Channel.
The recent preservation of Corg on the North Sea shelf is limited to 0.1x10^6 tons per year or about one tenth of the total preservation in the entire North Sea. On large parts of the shelf
sediments and organic matter are deposited only temporarily. The majority of the fine grained
sediments containing organic matter are transported over the shelf edge and deposited in the
Norwegian Sea, Skagerrak and Norwegian Channel.
Although on longer time scales (thousands of years) grain size (clay contents) explains the
variation in Corg contents of the sediments in time within each of the basins, it does not
explain the difference between the two. The Corg density (the amount of Corg per square metre
grain surface area) of the Skagerrak sediments is three times as high as in the Norwegian
Channel deposits. Curie point pyrolysis-gas chromatography-mass spectrometry shows that
there is a clear difference in the type of organic matter that is preserved in the Skagerrak and
Norwegian Channel. The sediments from the Skagerrak contain a higher percentage of
terrigenous organic matter than those from the Norwegian Channel. Since terrigenous organic
matter is more difficult to mineralize than marine organic matter, the total amount of Corg in
the Skagerrak sediments is higher.
If the North Sea is compared to other well studied shelf seas, than it becomes clear that the
preservation of Corg in the North Sea is very well comparable to present day preservation
processes on other shelves. All shelves show a Corg mineralization efficiency of 95% or more.
On most of the shelves none or only a very small fraction (<10%) of the preserved Corg is
buried in the shelf sediments. The remainder is transported over the shelf edge and stored in
canyons, on the continental slopes and abyssal plains. Only under exceptional conditions the
preservation of Corg in the shelf sediments is higher. In all cases the preservation of Corg is a
function of sediment accumulation rate, grain size and type of organic matter. On longer time
scales (glacials-interglacials) fine grained shelf sediments containing organic matter are eroded
and transported over the shelf edge, limiting the role of shelves as sinks for Corg even more.