Coring in Sigtunafjärden

Two cores where sampled in this lake basin in 1978-06-30 and three more in 1979-03-05. The upper part of one of these cores in shown below.

Radiograph of the upper part of core 480 from a depth of 31 m in the southeastern part of Sigtunafjärden. In this core the thickness of most of the faintly marked varves varied between 1 and 2 cm. The curve, showing the downcore variation in dry bulk density, is based on film-density values, recorded along the centerline of the radiograph.

This core expanded after sampling due to the formation and expansion of gas bubbles, which resulted from the reduced hydrostatic pressure and temperature rise. Therefore the core data are recalculated to represent in situ values.The expansion amounted to 6.3 cm about one day after sampling (increase in core length from 79.6 to 85.9 cm = 8 %). Down to a depth of 75 cm the mean value of the wet and dry bulk density amounted to 1.16 and 0.246 respectively, and the mean value of the organic content to 10.1 % (determined as the loss on ignition).

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