What are the types of sedimentary structures

The title of this article is ambiguous. Further meanings are listed under stratification (disambiguation).
Layers in the alpine shell limestone of the Partnach Gorge

The Layering is a characteristic of sedimentary rocks. However, volcanites and plutonites can also have stratifications, and the stratification can also be preserved during the metamorphosis of sedimentary rocks.

The sequence of layers mostly results from the sedimentation of different materials or changing deposition conditions. There can be differences in the mineralogical composition, grain size, color and texture.

The investigation of geological and pedological stratifications and their chronological assignment is called stratigraphy (stratification). The components contained in the individual layers and their fossils enable the temporal and genetic correlation with deposits of the same age, often distant.

Sedimentary structures

Sedimentary structures reflect the deposit conditions. They can be formed in the sediment or characterize the top or bottom of the layer. Sediment structures provide information on the type of transport (e.g. wind, flowing water, sedimentation from the water column), represent top-bottom criteria in folded areas, allow the direction of flow to be reconstructed and point to the living world.

Different sediment structures are:

  • Hummocky cross stratification (symmetrical ripple structures that were formed by oscillating storm waves. They therefore mainly occur in shelf areas from 30-50 m depth (only the convex parts of the ripples can be observed).)
  • Swalley cross stratification (As above, only the ripple valleys have been preserved; they occur in the deeper shelf environment.)
  • Herring bone stratification) (An opposite oblique stratification can be observed every few centimeters; this indicates a deposit in the shallow marine area with strong tidal influence.)
  • Flute marks (Missing material that was torn away by a storm event.)
  • Load casts (load marks can be observed on the underside of sediment layers; they arise from sudden superimposition of denser layers, which are pressed into the sediment.)
  • Flaser bedding (ripple structures filled with mud; they occur in the vicinity of changing flow conditions, e.g. in river mouths or under the influence of tides)
  • graded stratification - vertical grain size differentiation in one layer

See also

  • Facies, stratum
  • Bank, foliation