Duvnäsviken Bay

Coring sites in Duvnäsviken 1984-03-13.

Water depth during coring: 19 m (coring site 1000), 21 m (coring site 1001), and 19 m (coring site 1002).

Partly overlapping radiographs of the upper part of core 1000 from Duvnäsviken. The dark, more or less round or elliptical spots mark the presence of gas in bubble-phase. For location see the map above.

The upper, gas-rich deposits were very loose in this core, which expanded about 2 cm in length after sampling due to the formation and expansion of gas bubbles, which resulted from the reduced hydrostatic pressure and temperature rise.

Downcore variation in content of solids in the upper part of sediment core 1000, calculated from the recorded film density along the centerline of the radiograph.

The average wet an dry (salt-free) bulk density for the upper 0.2 m was as low as 1.03 and 0.05 respectively. The mean value of the organic content, determined as the loss on ignition, was high in this part of the core and amounted to 23 %. For the 50 years` period 1930 - 1980 the calculated mean annual rate of sedimentation at this coring site amounted to 0.322 kg/m² (4.6 mm). The salinity, the density , and the pH of the bottom water in the coring tube was 4.63 ‰, 1.004 and 7.32 respectively.

Sediment cores 1001 and 1002 were also gas-rich, very loose, and expanded in length after sampling, core 1001 about 3 cm and core 1002 about 2 cm. The differens in hardness index (the accumulated amount of solids in g/cm² down to a sediment depth of 10 cm) between the three cores 1000 - 1002 was inconsiderable. The value was very low and amounted to only 0.3.

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