Depositional environment
The seabed, in common with most landscapes, is shaped slowly and it has taken thousands of years to reach its present state. The depositional environment map shows which present-day processes are affecting the seabed. The map was compiled on the basis of the maps showing bottom sediments (particle size and mode of formation), and primarily shows where sediments are being eroded and deposited, and the current conditions on the seabed. Fine-grained sediments (mud and sandy mud) are mostly being deposited in the deepest areas. In shallower areas, there may be local erosion of fine-grained sediments on elevated areas, whereas sand is deposited on the lee side of those areas and where currents decrease in strength. Current erosion dominates in the shallowest areas, but here, too, fine-grained sediments may be deposited in depressions. An outwash layer of sandy gravel, cobbles and boulders remains on the seabed where the bottom currents are strongest. The strength of the bottom currents is indicated by the grain size of the sediments; mud shows weak currents and more coarse-grained sediments or erosion show stronger currents. The direction of bottom currents has so far been determined by studying the distribution of sediments in relation to areas where erosion and deposition are taking place. If transported sediments are lacking on one side of an iceberg plough mark, this shows that the current comes from that side and deposits sediments on its lee side. Modelling of bottom currents shows large variations in current direction and strength in accordance with the season and the tide cycle. In the continuation of the MAREANO program, detailed bottom current measurements and bottom current modelling will be carried out to support environmental studies and interpretations of depositional environments. |
