Gyttja (also gray mud floor or Mudde ) is an subhydrischer floor (underwater bottom ) in a well ventilated nutrient- rich waters or results from longer-term to perennial flooding / Überstauung. The gray to gray- black mud rich organisms consists of fine mineral material that is heavily infiltrated with organic materials, which are caused by large-scale reduction of plant and animal substances. They are ( or also called aggradation ) formed during the sedimentation.

Specified dry soils of this type are rich in nutrients and high water holding capacity, but the swell considerably when changing moisture and shrink.

If the mud sauerstofflos and therefore hardly enlivened, it is called digested sludge ( sapropel ).

The term goes back to the Swedish term for "mud " or " silt " and was introduced by Hampus of Post 1862 in the scientific literature.


  • Soil type
  • Clastic sedimentary rock
  • Biogenic sedimentary rock
  • Sedimentation