Sedimentary rocks form the surface part of the earth's crust. Such rocks belong to the Quaternary period. They are called sedimentary due to the fact that they are formed as a result of chemical and physical processes, as well as the vital activity of organisms. As a rule, these are deposits of small thickness, high mobility and weak connectivity.
Sedimentary rocks include:
- eluvial;
- proluvial;
- glacial;
- water-glacial;
- deluvial;
- lake;
- loeslike;
- alluvial;
- marine;
- eolian.
What is eluvium?
Let's take a closer look at eluvial deposits. Eluvium is the products of rocks formed as a result of weathering and not mechanically moved. There are a lot of types of this sedimentary material, since there are a large number of rocks, any of which is subject to destruction. In many ways, the composition of eluvium and its thickness depend on climatic factors and geographical location. In cold or dryconditions are dominated by physical weathering. In wet - chemical.
What is weathering?
Weathering, that is, a set of processes that destroy rocks or minerals, can be physical and chemical. Most often, rocks are exposed to these two types of weathering simultaneously or sequentially. Weathering factors include precipitation, time, temperature, humidity, and the presence of living organisms. If the rocks are loose or there are many cracks in them, then the destruction process will occur faster.
How to distinguish eluvium?
Main signs of eluvial rocks:
- are located at the site of the collapse of the original rock, while maintaining its frame and filling all the cracks;
- gradually form the original breed;
- ragged lower bound;
- consists of clay, ore, metals;
- no division into layers;
- contain particles of different size and composition.
How to determine weathering zones by profile?
Weathering zones can be used to determine how eluvium is formed.
The formation of eluvium occurs as follows. Under the action of the wind, various processes occur that form cracks. The cracks then widen and the debris falls down onto the parent rock. Over time, the parent rock is under a layer of large blocks. A small amount of debris fills the empty spaces. The upper clastic material becomes smaller and can be worn down to the smallest particles lining the upper horizon.
Zonesweathering:
- The zone of complete crushing is the uppermost part of the deposits, which is practically impermeable and plastic due to the presence of clay particles. The zone is composed mainly of small rock particles.
- The rubble zone is the next after the top one. It is named so because of the content in it of detrital material the size of rubble. This zone is permeable to water and contains almost no clay particles.
- Blocky zone - large fragments of parent rock formed as a result of weathering cracks. Water permeability is strong. It is important to note that the deeper, the larger the debris. If the bottom in this zone can be blocks with a diameter of more than a meter, then the top is most often located small fragments.
- Monolithic zone - the lowest zone, composed only of the parent rock, is an integral layer. Small cracks in the rock are filled with clay material.
Carbonate eluvium
Limestone eluvium is a reddish-brown rock composed of clays, loams, parent rock detritus and carbonates. In composition, it resembles marl eluvium, which is distinguished by an even higher content of clay particles. The properties of these two types of rocks include alkalinity, a high content of magnesium and calcium.
Soils on the eluvium of limestone and marl
Such soils contain a large amount of bases in their composition. They are characterized by low power, since eluvium is a sedimentary material. The advantage of alkaline soils is that they are goodare drained. However, this can also be a disadvantage during dry periods when plants lack water and minerals.
Clastic materials make processing difficult. Due to the content of macroelements in the soil, humus is formed, which increases fertility. It is precisely due to calcium and magnesium that these eluviums are considered one of the most favorable for use in the temperate and subarctic climatic zones.
Building on eluvium
Since weathering processes are constant, the possibility of building on these rocks should be assessed taking into account their further changes. Most often, eluvium is new deposits. They withstand static load worse, are subject to various physical, chemical and biological processes. Because of this, they are usually removed from the construction site and cannot be used as structure foundations.
