Sedimentary Rock – Sedimentary rock is a rock that is formed from the compaction of sediment in the form of loose material. Sedimentary rock can also form from consolidation of sediments, as loose material, which is then transported to the site of deposition by wind, water, ice and gravity avalanches, ground movements.
Apart from being formed from sediment consolidation, sedimentary rocks can also form due to the evaporation of calcium carbonate solutions, salts, silica, and various other materials.
Sedimentary rocks are widely distributed on the earth’s surface. Although the thickness of sedimentary rocks is actually relatively thin, which is around 0 to 13 kilometers and only 2.2 kilometers will later be exposed on the continent. Sedimentary rocks are also a small covering of the earth’s crust, which is only about 5% of all these rocks are in the earth’s crust.
The process of abrasion or breaking of rock so that it settles into sedimentary rock itself can be done in several ways, namely by being deposited somewhere or through a mechanical sedimentation process, by evaporation which causes concentration and precipitation of saturated solutions or chemical sedimentation processes, biochemical processes as well as biomechanical processes (organic sedimentation processes), can also be formed primarily from magma or through volcanic sedimentation processes.
About Sedimentary Rocks
There are so many types of rocks that are around us. One type of rock is sedimentary rock. besides that there are also types of igneous rocks and metamorphic rocks. Sedimentary rock is a type of rock that is formed as a result of compaction of sediment in the form of loose material.
Sedimentary rock is rock that is formed from the deposits of various materials carried by wind or water. In addition, there is another understanding of sedimentary rocks, namely rocks that are formed due to the lithification process or the process of petrification from the results of weathering and soil erosion that have been carried away by currents and then settled.
An expert, Hutton in 1875 stated that sedimentary rocks are rocks formed by consolidation of sediments, as a loose material, which is then transported to the location of deposition by ice, water and, wind, as well as gravitational avalanches, ground movements or also landslides.
Apart from being formed from this, sedimentary rocks are formed by the evaporation of a solution of calcium carbonate, silica, salt, and also other materials. Besides that, did you know that sedimentary rocks actually have a very large number and are spread on the surface of the earth in this world?
Even according to Tucker in 1991, that 70% of the rock found on the entire surface of the earth is part of the type of sedimentary rock. But the rock is only 2% of the volume of the entire earth’s crust. This then indicates that the sedimentary rocks are spread very widely but the thickness is relatively shaped.
The earth’s crust itself is composed of various materials, not only rocks but also layers of soil, sand, and others. And these rocks are included in the elements that make up the composition of the earth’s crust.
The Process of Forming Sedimentary Rocks
Sedimentary rocks before they form undergo a process of compaction and compaction from loose material or sediment until they finally become intact sedimentary rocks. This process is then also known as diagenesis.
The diagenetic process itself can occur at atmospheric pressure and temperature up to 300 degrees Celsius and also a pressure of 1-2 kilobars which lasts from the time the sediment is buried until it is finally lifted and exposed again above the surface of the earth’s atmosphere.
Based on this, there are 3 types of diagnosis.
1. Eogenic Diagnosis
This diagnosis is the initial diagnosis which then occurs in sediments below the surface of the water.
2. Mesogenic diagnosis
This diagnosis is a diagnosis that occurs when the sediment is buried deeper.
3. Telogenic diagnosis
Is a diagnosis that occurs when sedimentary rocks are then exposed back to the earth’s surface caused by uplifting and erosion.
Those are the various kinds of diagnoses that occur in sedimentary rocks. Because of the various types, the degree of cohesiveness of these sedimentary rocks then consists of various kinds and varies.
Various kinds of cohesiveness of these rocks include loose materials, which are still in the form of deposits or sediments. At this stage material consolidation then occurs in dry conditions. But this will also decompose if put in water.
Sedimentary Rock Texture
Sedimentary rocks have a variety of textures. These sedimentary rocks can also have clastic textures or non-clastic textures. However, if the rock is very compact and has recrystallized or recrystallized again, then the sedimentary rock also has a crystalline texture.
Sedimentary rocks with a crystalline texture generally occur in types of limestone and sedimentary rocks rich in silica which are very compact and hard. Thus some information about sedimentary rocks that are widely found around us.
As a rock that is widely found around us, this sedimentary rock has many uses, especially for building materials or as a medium for decorating houses and buildings today. Such is the information about sedimentary rocks that we can learn so that you can then distinguish one type of rock from other rocks.
Types of Sedimentary Rocks
Sedimentary rocks are formed from igneous rocks and various other solid substances which then experience erosion in a certain place and eventually settle down to become hard. These sedimentary rocks generally also have a horizontally layered shape.
Did you know that this type of sedimentary rock can still be divided into several types? The types of sedimentary rocks will then be classified according to several categories. Many experts categorize or classify types with different numbers. Then, what are the types of these sedimentary rocks?
Sedimentary Rock According to Pettijohn (1975), O’Dunn and Sill (1986)
Pettijohn in 1975 and O’Dunn and Sill in 1986 divided sedimentary rocks based on their texture which are further divided into two major groups, namely clastic sedimentary rocks and non-clastic sedimentary rocks:
- Clastic sedimentary rock or also known as detritus, mechanical, exogenous sedimentary rock which is also a sedimentary rock consisting of clastics or rock debris that settles naturally or mechanically by its own gravity.
This type of rock is then formed as a result of rework or rework from pre-existing rocks. The reworking process that occurs as the formation of this rock itself includes erosion, transportation, weathering, and also redeposition or re-deposition.
- Non-clastic sedimentary rock is then a type of sedimentary rock group formed as a result of the evaporation of a solution or deposition of material in that place.
The process of rock formation can also occur by chemical, biological or organic processes, or a combination of the two, namely a combination of chemical, organic and biological. The process which is a combination of the two is also called a biochemical process.
Sedimentary Rock According to Sanders 1981 and Tucker 1991
According to Sanders in 1981 and Tucker in 1991 then classify or divide these sedimentary rocks into four categories namely:
- Sedimentary rocks detritus or clastics Chemical sedimentary rocks as sedimentary rocks that are formed through a chemical reaction, such as precipitation, evaporation, and also concentration. Examples of these chemical sedimentary rocks include salt rock, gypsum rock, stalactites, and also stalagmites.
- Organic sedimentary rock – Organic sedimentary rock, also known as sedimentary rock of bodily origin. Organic sedimentary rock itself is a sedimentary rock that comes from the remains of living bodies or is made by a living body. This type of rock group can then be broken down into two types, namely biomechanical sediments and also biochemical sediments.
Biomechanical sediment is a deposit of the remains of living body parts that settle naturally under their own weight, for example in limestone, shell rock, numilites, and also layered limestone. While biochemical sedimentary rock is a type of rock that occurs due to the deposition of limestone and silicium elements with living rock.
Sedimentary Rock According to Graha (1987)
This type of sedimentary rock is a sedimentary rock that is generally non-classical in texture. Graha in 1987 also divided these sedimentary rocks into four groups as well, which include:
- Detritus or clastic sedimentary rock, mechanical
- Coal or organic sedimentary rock and vegetation
- siliceous Sedimentary Rock,
- Carbonate sedimentary rock
Especially for this type of rock and also for siliceous sedimentary rocks, these are clastic sedimentary rocks and non-clastic sedimentary rocks. Then if it is based on the composition of its main constituents, clastic sedimentary rock or clastic textured, then it can be further divided into three types, namely:
- Siliciclastic sedimentary rock. This type of rock is a type of clastic sedimentary rock whose main constituent minerals are feldspar and quartz.
- Then there are also volcanic clastic sedimentary rocks. Volcanic sedimentary rock is a type of sedimentary rock with the main constituent material coming from volcanic activity, such as glass, crystal, and/or lithic.
- Carbonate clastic sedimentary rock or also known as limestone This type of rock is a clastic sedimentary rock with the main constituent mineral being carbonate material (calcite).
Those are the types of clastic sedimentary rocks according to their main constituent composition.