Gulf of Finland

Radiographic analyses of sediment cores.

Radiographs of the upper part of cores GF1 and GF2, both from a depth of 84 m in the south-western  and in the central part of the Gulf of Finland respectively (stations no. 181 and 182).

There is a considerable difference in sediment density between the softer, laminated upper part and the harder, bioturbated lower part of these cores, as shown for core GF1 by the curve below. The deposits in the uppermost part are reworked, possibly a consequence of trawling.

Downcore variation in content of solids in core GF1.

Partly overlapping radiographs of sediment core GF4 from a depth of 35 m in the southeastern par of the Gulf of Finland (station no. 183).

The density of this core was high in relation to the other X-rayed cores from the Gulf of Finland. The hardness index of this core was the second highest of the 34 cores, X-rayed during the Baltic Sediment Baseline Study in 1993.

Downcore increase in accumulated amount of solids in the upper part of the seven X-rayed sediment cores from the Gulf of Finland.

Partly overlapping radiographs of the upper part of core XV-1 from a depth of 61 m in the north-eastern part of the Gulf of Finland (station no. 187).

This core expanded 3 cm (6 %) in two hours after sampling. A cyclic variation between harder and softer layers can be found in the upper part of this core. If we assume that the three upper layers from a core depth of 0.7-3.9 cm and the five layers from a core depth of 13.7-19.5 cm are annual, then the mean annual rate of sedimentation for these parts of the core amounts to 2.0 kg of solids/m²/yr. If we assume that this value is also valid for the rest of the core, then the mean annual rate of sedimentation is 12.3 mm in thickness for the upper 20 cm and 9.5 mm for the upper half-meter of this core

Downcore variations in content of solids in the upper part of core XV-1. The given chronology and the given sedimentation rates are somewhat uncertain. In this core the annual layers are best preserved at a core depth of 14-20 cm.

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