Autocompaction of shallow silty salt marsh clay

Empirically derived algorithms are suggested by means of which it is possible to evaluate relations between physical properties in silty salt marsh clay. A relation between loss on ignition, sand content and bulk dry density in the topmost 5 cm was found to explain 84% of the variation of the latter. The bulk dry density in the topmost ≈ 0.5 m was found to vary as a logarithmic function of depth below the surface controlled by two constants directly dependent on the bulk dry density in the topmost 5 cm. Integration of this function illustrates that mass depth (MSDz) down core can be directly related to the bulk dry density of the surface layer. For sediments with a surface bulk dry density between 400 kg m− 3 and 800 kg m− 3 the porosity was found to vary (+/−10%) with MSDz as another logarithmic function. The results allow for an evaluation of the use of marker horizons in the topmost layers. Right after such a layer has been spread on the surface, sedimentation measured in length per time (accretion), will be significantly larger than for subsequent periods. Using marker horizons, it is therefore not trivial to know the level of the marker, as deeper located markers will indicate successively smaller accretion rates with the same sediment input.