Cores from Kattegatt
The two cores, partly shown by the radiographs below, was sampled from and X-rayed on board R/V Aranda in connection with the ICES/HELCOM baseline study on contaminants in Baltic sedimens in 1993. Secondary, biogenic structures dominate in these two cores. In general the tube burrows were filled with sediment of less density (darker on the radiographs) than the surrounding sediment.
Radiograph of the topmost part of sediment core K1 (Kattegatt 1, station no. 155, depth 28 m) with bottom water on top.
This core from the southeastern part of Kattegatt was very compact also in the uppermost part and had a hardness index of 7.8. In the uppermost cm the mean value of the dry and wet bulk density amounted to 0.48 and 1.32 respectively, and the porosity to 83 %. The sedimentary structures, shown by the radiograph, reflect periods with high dynamic activity at the sediment-water interface. The sedimentary sequence is reworked both due to bioturbation and to erosion (and perhabs also due to trawling).
Radiographs of the upper part of sedimet core K2 from the northern part of Kattegatt. (Kattegatt 2, station no. 156, depth 75 m). The lead letters O and X are used for marking corresponding levels on the partly overlapping radiographs.
The hardness index of this bioturbated core was 3.5. In the uppermost cm the mean value of the dry and wet bulk density amounted to 0.22 and 1.17 respectively, and the porosity to 91.5 %. The downcore increase in accumulated amount of solids was comparatively high also in this core.
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