Depositional environment

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Main depositional environments.svg

In geology, depositional environment or sedimentary environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record. In most cases the environments associated with particular rock types or associations of rock types can be matched to existing analogues. However, the further back in geological time sediments were deposited, the more likely that direct modern analogues are not available (e.g. banded iron formations).

Types of depositional environments

Diagram to show the different depositional environments in which tsunami deposits are formed - partly after Shanmugam 2006 [1]
Depositional environmental model of the Araripe Basin formations, NE Brazil

Continental

Transitional

  • Deltaic – Silt deposition landform at the mouth of a river
  • Tidal
  • Lagoonal – A shallow body of water separated from a larger body of water by barrier islands or reefs
  • Beach – Area of loose particles at the edge of the sea or other body of water
  • Lake – A body of relatively still water, in a basin surrounded by land

Marine

Others

  • Evaporite – A water-soluble mineral sediment formed by evaporation from an aqueous solution
  • Glacial
  • Volcanic
  • Tsunami – Sedimentary unit deposited by a tsunami

Recognition of depositional environments in ancient sediments

Depositional environments in ancient sediments are recognised using a combination of sedimentary facies, facies associations, sedimentary structures and fossils, particularly trace fossil assemblages, as they indicate the environment in which they lived.

References

  1. ^ Shanmugam G. (2006). "The Tsunamite Problem" (PDF). Journal of Sedimentary Research. 6: 718–730. doi:10.2110/jsr.2006.073.
  • Harold G. Reading. 1996. Sedimentary Environments: Processes, Facies and Stratigraphy. Blackwell Publishing Limited.

External links

  • Sedimentary Environments Classification Charts
  • Depositional environments on e-notes
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