Geopetal structure

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Fossil spirit level

Geopetal structures are structural features that serve to determine the chronological deposition sequence of sedimentary rocks . Taking into account the stratigraphic principle , they are important criteria for differentiating between normally stored and overturned structures.

The following main types are distinguished:

  • Internal structure - layer characteristics that can be found within a layer
  • External structure - structural features on the layer surfaces
  • Tectonic fabric - relationships between stratification and foliation

Internal structure

Within a rock layer, the following can serve as characteristics of the storage sequence:

  • graded stratification - vertical grain size differentiation
  • sessile animals in the sediment in living position - e.g. B. corals
  • Worm burrows
  • partially filled cavities, especially in fossils, the filling of which points downwards in the direction of gravity. This sometimes even allows subsequent tilt angles to be determined ("fossil spirit levels")
  • Oblique stratification within the layer
Internal structure Geopetal Reiki.jpg

External structure

At the layer boundaries and on the layer surfaces, the geopetal structures serve:

  • asymmetrical flow ripples ( ripple marks )
  • Oscillation ripples
  • Regulated mussel shells, the convex side of which shows "up", as they are tilted by the current
  • Dry cracks - pointed wedges point downwards
  • Rock salt pseudomorphs - prints point upwards
  • Raindrop impressions in the sediment
  • Animal traces of life in general, as far as identifiable
  • Root soils ( coal )
  • Washout marks
  • Debit marks
  • Grinding marks
  • Erosion and transgression discordances
External structure Geopetal Reiki.jpg

Tectonic structure

The relationship between stratification and foliation applies:

  • when stratification and foliation collapse in the same direction
    • Storage normal if the stratification is shallower than the foliation
    • Storage tips over when the stratification is steeper than the foliation
  • if stratification and foliation collapse in opposite directions, storage is always normal

The positional relationship of "drag-folds" to a large fold can also serve as a geopetal structure.


  • Bruno Sander : Contributions to the knowledge of the accumulation structure (rhythmic limestone and dolomite from the Triassic) . Mineralogisch-Petrologische Mitteilungen, Volume 48, 1936, pp. 28-209
  • Robert R. Shrock : Sequence in layered rocks - a study of features and structures useful for determining top and bottom or order of succession in bedded and tabular rock bodies . New York 1948, 507 pp.
  • B. Hückel & Volker Jacobshagen : Geopetal sedimentary structures in the main dolomite and their significance for the tectonic analysis of the Northern Limestone Alps. Journal of the German Geological Society, Volume 113, 1961, pp. 305-310
  • Adolf Seilacher : Preservational history of Ceratite shells . Palaeontology, Vol. 14, 1971, pp. 16-21