Oceanologia (Jun 2006)
Spatial variability of recent sedimentation rates in the Eastern Gotland Basin (Baltic Sea)
Abstract
In order to study recent sedimentation rates in the Eastern GotlandBasin, 52 short sediment corescollected fromthe deepest part (< 150 m) of the Basin in 2003were investigated.The upperparts of all the cores were distinctly laminated and dark incolour, followed by a homogeneous, greyish lower part. The thicknessof the laminated sequences varied from 17 to 300 mm. 210Pb datinganalyses of selected cores revealed that the change from non-laminatedto laminated sediments happened about 100 years ago, indicatinga shift from predominantly oxic bottom water conditions to anoxicconditions. Used as a time marker, this shift in the sedimenttexture enabled sediment accumulation rates to be estimated forall sediment cores. The observed mean linear sedimentation ratefor the whole basin was 0.93 ± 0.67 mm y-1. The respectivebulk sediment accumulation rates ranged from 10.5 to 527 g m-2 yr-1with an average of 129 ± 112 g m-2 yr-1, indicatinga high spatial variability of sedimentation rates within thebasin. This agrees very well with the long-term sedimentationpattern since the Litorina transgression. The observed patternclearly reflects the hydrographic conditions at the seaflooras studied by modelled near-bottom current velocities.
