SEDIMENTARY ENVIRONMENTS: CHARACTERISTICS AND MAIN TYPES - GEOGRAPHY - 2024

The sedimentary environments are areas of the earth surface where deposited and build up large volumes of solid material (sediment) which were transported by atmospheric agents climate-erosion.

This phenomenon is studied in detail by geology, especially to understand and recreate the terrestrial conditions of the past. The accumulation of sediment in the soil of a place compacts the solid material over time, forming what are called sedimentary rocks.

The composition of these rocks will vary depending on the climatic conditions of the moment, the place and the transporting agents involved. When studying the composition of the soil and its sedimented material, much of this information is interpretable.

They can have very varied physical, chemical and biological properties that can be translated into types of material (mineral or organic), sizes, place of origin, temperature at which it was processed, salinity, oxidation, pressure, degree of acidity (pH) and the time or era in which it was cemented.

Sedimentary environments such as canyons, coastal rocky cliffs and rocky deserts show on the ground and on the walls the material solidified over centuries in typical horizontal layers or facies, one above the other.

Classification according to the type of participating agent

The types of sedimentary environments can be classified according to the climate in which they occur, the geometric composition of the sediments, the sequence of facies and the type of climatic-atmospheric agent of the phenomenon.

This last classification is the best known and is the one that will be explained below.

1- Terrestrial sedimentary environments

They are the areas whose sedimentation process occurs on land. In this case, it is the water, wind and ice that erode, transport and deposit the solid material on the ground. These environments are independent of the influence of the maritime coasts and their natural agents.

Geology recognizes 5 types of terrestrial sedimentary environments:

River

It is the one that most commonly exists in the terrestrial areas of the planet. Rivers are the agent of massive transport of large volumes of sediments, and they deposit the material along the water banks and on the floor of the river bottom.

Inclined or high velocity channels tend to deposit medium and large rocks. Where the speed of the river decreases, the soil and banks present smaller material, such as sand and gravel. If the water movement is very minimal, mud can form.

The action of rivers is one of the agents that most shapes the landscape through which it flows.

Alluvial

It occurs at specific times due to transitory water currents resulting from heavy rains or floods.

Lacustrine

It occurs as a result of the water deposit from rainfall and internal rivers. When the speed of the water reaches the lake, lagoon or pond, solid materials are deposited on the ground at different distances both from the shore and from the water inlets.

That distance depends on the speed with which the water is moving. Far and deep, mud forms on the ground. The banks are usually sandy and in the vicinity of the water inlets there is larger material, such as gravel or small rocks.

Glacial

It is the sedimentary environment that exists where the accumulation of snow forms ice. It generally occurs in the heights or in very cold areas. This accumulation of ice also deposits sedimentary material.

Depending on the time and pressure, some sediments may have been part of the soil, which ended up being detached due to the force of the glacier moving downhill. This movement is usually very slow in time or extremely sudden.

Wind

It occurs in areas with little rainfall and scarce rivers. The driest areas of the planet, such as deserts, are only affected by the wind due to the transport and deposit of solid material.

The action of the wind takes off tiny particles from the rocks, which are responsible for forming sandy dunes. However, the soil erodes when the rains arrive and it is the water that carries larger material.

2- Marine sedimentary environments

They occur in the interior of the oceans and independent of coastal agents and phenomena. Sediments can be transported by ocean currents and accumulate anywhere on the ocean floor.

The depth and slope of the soil is also an important factor in the movement of sedimentary material.

Coral reefs are shallow sedimentary environments and are formed by the interaction of marine animals and mineral material carried by currents. These can grow quickly where they receive more nutrients from the sediment deposit.

In the depths there are abyssal sedimentary environments and continental shelf. These have very little solid ground material.

The platform ones receive more sediment from the expulsion of material from the movements of the tectonic plates

3- Sedimentary transition environments

They are those that exist from the interaction of water on the coasts in a complex system intertwined between terrestrial and marine processes. Both rivers and waves are carriers of many sediments, and these shape coastal landscapes.

Beaches are the most common coastal sedimentary environments. They are usually made up of sand and gravel that has been eroded, transported and deposited over centuries by the movement of waves against the ground.

Where the force and energy of the tide and waves are low, terrestrial processes dominate and the sedimentary environments of delta are formed, product of the mouth of the rivers. Here it is the sea that receives the greatest amount of sediment from the land.

Otherwise, where the mouth is weak and the tide and waves are strong, the sediments of the river are returned together with material carried by the sea currents. In these cases the delta is flooded with seawater and the well-known rivers of salt water are formed.

Intertidal zones occur on coasts whose tides change frequently in short periods of time. They are large areas that remain covered during high tide and uncovered during the retreat from the sea.

On some coasts there may be sedimentary albumen environments, which form salty lagoons. They are usually separated from the visible sea by thin cords of land or sand, but may be connected to the sea at small points.

References

1. Ondine Evans (2009). Sedimentary Environments. Australian Museum. Recovered from australianmuseum.net.au
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3. This Old Earth. Sedimentary Environments. Recovered from thisoldearth.net
4. Science Encyclopedia. Sedimentary Environment. Recovered from science.jrank.org
5. Vic Di Venere. Sedimentary Environments - Historical Geology Notes. Earth and Environmental Sciences. Columbia University. Recovered from columbia.edu
6. Thomas R. Holtz, Jr (2014). Terrestrial Sedimentary Environments - Historical Geology. University of Maryland - Department of Geology. Recovered from geol.umd.edu