Sediment facies and hydrodynamic setting: a study in the south western Baltic Sea

Abstract

This study aims at investigating the relationship between sedimentary facies and hydrodynamic setting by applying statistical analysis of sedimentological data and hydrodynamic modelling. The facies description bases on a dataset of grain-size analysis of surface sediments of the southwestern Baltic Sea. The facies is described by the grain-size parameters median, sorting, and skewness – parameters of a distribution function fitting the grain-size data. The function was derived from a formula proposed by Tauber (1995). The three grain-size parameters were mapped for the southwestern Baltic Sea area applying ordinary kriging (Journel and Huijbregts 1978). The study area was subdivided into uniform facies regions using the concept of regionalized classification after Harff and Davis (1990). The near-bottom hydrodynamic conditions controlling sediment deposition are represented by the average kinetic current energy, the average kinetic wave energy, and the average current vector derived from results of numerical modelling covering a period of 1 year (Rietz et al. 2000). Transport pathways in the southwestern Baltic Sea were postulated based on the directions of the average current vectors which are assumed to be the preferred directions for clastic material transport. A comparison of the hydrodynamic conditions at selected test locations along the preferred transport pathways with the granulometric facies reveals the common case of a direct genetic dependency between the surface sediment facies and the recent hydrodynamic setting. An exception occurs within the Pomeranian Bight. Results indicate that the sediments of this area have not been accumulated under the present-day conditions which supports the findings of Wehner (1990) reporting a glacio-fluviatile late Pleistocene genesis of the sediments there.