Northern Baltic Proper

Partly overlapping radiographs of the upper part of core LL (= core LL19) from a depth of 200 m in the Northern Baltic Proper (station no. 180, the uppermost part in stereo).

The black, round and elliptical spots mark the presence of gas in bubble-phase. The upper 0.3 m of this core expanded about 10 % in length (in the coring tube) after sampling due to the formation and expansion of gas bubbles, which resulted from the reduced hydrostatic presssure and temperature rise. Therefore the core data are recalculated to represent in situ values.

Downcore variations in content of solids in the upper part of core LL (=LL19). The given chronology is somewhat uncertain. The lowest density values are due to the presence of gas in bubble-phase.

Downcore variations in content of solids in core LL19. From Axelsson 1997 (SGU series Ca 86).

The uppermost, gas-rich part is very loose in relation to the lower, bioturbated. The average dry bulk density for the core depth 0.40-0.75 m is 7 times higher than for the uppermost 0.30 m of the core (after core expansion). This is reflected also by the given values of linear sedimentation rate. These, rather uncertain values, are based on the assumption that the layering is seasonal in the upper part of the core and that the mass accumulation rate here is representative also for the rest of the core.

Radiographs of the uppermost part of cores LL1 and LA.

Core LL1 is from a depth of 166 m (station 180S, secondary station), rather close to coring station LL19 (=station no 180). Core LA is from a depth of 215 m in the Landsort Area (station no. 179). A number of thin couplets on top of a dense network of tube burrows characterizes these cores. The tube burrows are filled with sediment of less density (darker) than the surrounding sediment.

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