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{{Short description|Processes associated with the deposition of a particular type of sediment}}(File:Main depositional environments.svg|thumb|320px|right|A diagram of various depositional environments)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

(File:Tsunami deposit environments.png|thumb|400px|Diagram to show the different depositional environments in which tsunami deposits are formed – partly after Shanmugam 2006 JOURNAL, Shanmugam G., 2006, The Tsunamite Problem,weblink Journal of Sedimentary Research, 6, 5, 718–730, 10.2110/jsr.2006.073, 2006JSedR..76..718S, )(File:Araripe Basin - depositional environments and sequence stratigraphy.jpg|thumb|Depositional environmental model of the Araripe Basin formations, NE Brazil)ContinentalWEB,weblink Basics—Table of Depositional Environments, commons.wvc.edu, 2020-01-13, JOURNAL, Earle, Steven, September 2015, 6.3 Depositional Environments and Sedimentary Basins – Physical Geology,weblink Physical Geology, 2020-01-13,

• {{annotated link|Alluvial}} – type of Fluvial deposit. Caused by moving water in a fan shape (Alluvial Fan) and containing mostly impermeable and nonporous sediments well sorted.
• {{annotated link|Aeolian processes | Aeolian}}. Often in deserts and coastal regions and well sorted, large scale cross-beds
• {{annotated link|Fluvial}} – processes due to moving water, mainly streams. Common sediments are gravel, sand, and silt.
• {{annotated link|Lacustrine deposits|Lacustrine}} – processes due to moving water, mainly lakes. Common sediments are sand, silt, and clay.

Transitional

• {{annotated link|River delta | Deltaic}} (possible cross beds, ripple marks)WEB,weblink Basics—Table of Depositional Environments, commons.wvc.edu, 2020-01-13, Common sediments are sand, silt, and clay.
• {{annotated link|Tide}} – processes due to tidal currents, creates tidal flats (fine-grained, ripple marks, cross-beds).WEB,weblink Basics—Table of Depositional Environments, commons.wvc.edu, 2020-01-13, Common sediments are silt and clay
• {{annotated link|Lagoon | Lagoonal}}. Little transportation, creates lagoon bottom environment. Common sediments are carbonates (in tropical climates).
• {{annotated link|Beach}}. Caused by waves and longshore currents. Creates beaches, spits, and sandbars with the common sediments of gravel and sand.
• {{annotated link|Lake}}

Marine

• {{annotated link|Shallow water marine environment}} – processes due to waves and tidal currents, creates shelves and slopes, lagoons. Common sediments are carbonates (in tropical climates) or sand, silt, and clay (elsewhere)
  • {{annotated link|Upper shoreface}}
  • {{annotated link|Lower shoreface}}
• {{annotated link|Abyssal plain|Deep water marine environment}} (abyssal plains) caused by ocean currents. Common sediments are clay, carbonate mud, silica mud.
• {{annotated link|Reef}} caused by waves and tidal currents. Also creates adjacent basins. Common sediments are carbonates.

Others

• {{annotated link|Evaporite}}
• {{annotated link|Glacial}}
  • Till – angular to rounded grains, poorly sorted, unstratified (massive)
  • Outwash – ripple marks, cross-beds, similar to stream channelWEB,weblink Basics—Table of Depositional Environments, commons.wvc.edu, 2020-01-13,
• {{annotated link|Volcanic}}
• {{annotated link|Tsunami deposit|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

{{Reflist}}

• Harold G. Reading. 1996. Sedimentary Environments: Processes, Facies and Stratigraphy. Blackwell Publishing Limited.

External links

• weblink" title="web.archive.org/web/20090228095248weblink">Sedimentary Environments Classification Charts
• Depositional environments on e-notes