Radiograph of the two uppermost varves (the deposits in 1976 and in 1975) in core 156 from a depth of 52 m in the southern part of lake Lilla Ullfjärden. The dark, round and elliptical spots mark the presence of gas in bubble-phase. Date of coring: 1977-03-23. From Axelsson 1979 (Ymer 99).

The length of this gas-rich core increased by about 12 % (in the coring tube) during part of the day of sampling, that is from 57.7 cm just after sampling in the morning to 64.5 cm just before X-raying in the afternoon. This expansion was a result of reduced hydrostatic pressure and temperature rise.

Stereoradiographs of concretions in core 641 from a depth (during sampling) of 24.5 m in lake Lilla Ullfjärden.

Click here to get a better resolution of the stereoradiographs.

A comprehensive study of the deposits in the lakes Lilla Ullfjärden and Stora Ullfjärden was published by Laila Bodbacka Fältman in 1993 (Fältman, L. Bodbacka, 1993: Sedimentary structures and sediment accumulation in the lakes Lilla Ullfjärden and Stora Ullfjärden, studied by the X-ray radiographic technique. UNGI Rapport Nr 83, 119 pp). Her description of sedimentary structures in Lilla Ullfjärden was based on radiographs of 91 sediment cores.

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