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Definition of Sedimentary Rock
Sedimentary rock is one type of rock which is formed as a result of compaction of sediment in the form of loose material. Sedimentary rocks or often also referred to as sediments are rocks that are formed from deposited materials carried by water or wind. There is another understanding of sedimentary rocks, namely rocks formed due to the process of petrification or lithification from the results of weathering processes and also soil erosion.which has been carried away by the current and then deposited. An expert, namely Hutton (1875) stated that this sedimentary rock is a rock formed by sediment consolidation, as loose material, which is transported to the depositional location by water, wind, ice and also gravitational avalanches, soil movements or landslides. Besides being formed from this, these sedimentary rocks are also formed by the evaporation of a solution of calcium carbonate, silica, salt, and other materials. This is what is called sedimentary rock.
Did you know that these sedimentary rocks are very numerous and widely spread on the earth's surface in this world? Even according to Tucker (1991), that 70% of the rocks found on the entire surface of the earth is a type of sedimentary rock. But the rock is only 2% of the volume of the entire earth's crust. This indicates that sedimentary rocks are spread very widely on the earth's surface, but their thickness is only relatively thin. The earth's crust is indeed composed of various kinds of materials, not only rocks but also layers of soil, sand, and others. And these rocks also include elements that make up the composition of the earth's crust . The rocks that make up the composition of the earth's crust are divided into various types and one of them is this sedimentary rock.
Sedimentary Rock Formation Process
This sedimentary rock undergoes a process of compaction and also compaction of loose material (sediment) to become a solid sedimentary rock. This process is known as diagenesis. The diagenetic process itself can occur at atmospheric temperatures and pressures up to a temperature of 300 degrees Celsius and also a pressure of 1-2 kilobars which takes place from sediment experiencing burial to being lifted and also exposed again above the surface of the earth's atmosphere . Based on this, there are 3 types of diagnosis, namely:
- Eogenic diagnesa, namely the initial diagnesa that occurs in sediments below the water surface.
- Mesogenic diagnosis, namely the diagnesa that occurs when the sediment undergoes a deeper burial.
- Telogenic diagnosis, which occurs when sedimentary rocks are exposed back to the earth's surface due to uplift and erosion.
Those are the various types of diagnesa that occur in sedimentary rocks. Because there are various kinds of this diagnosis, the degree of compactness of these sedimentary rocks also varies or varies. Various kinds of compactness of these sedimentary rocks include:
- Loose materials, namely those that are still in the form of deposits or sediments.
- Solid or indurated. At this stage the consolidation of the material occurs in dry conditions. However, it will decompose when put into water.
Those are some types of compactness that occur in sedimentary rocks. After we study the compactness of sedimentary rocks, then we will learn about the texture of sedimentary rocks.
Sedimentary Rock Texture
As previously stated, these sedimentary rocks have a variety of textures. Sedimentary rock can be textured clastic or non-clastic. However, if the rock is very compact and if recrystallization or re-crystallization has occurred, then this sedimentary rock has a crystalline texture. Sedimentary rocks that have a crystalline texture generally occur in limestone and also silica-rich sedimentary rocks which are very compact and hard.
That's some information about sedimentary rocks that are widely available around us. As rocks that are widely found around us, these sedimentary rocks have many uses, especially for building materials or to decorate homes and buildings today. Thus information about sedimentary rocks that we can learn so that we can distinguish this type of rock from other rocks.
Types of Sedimentary Rocks
Sedimentary rocks are formed from igneous rock or other solid substances which are then eroded in certain places and then settle and eventually become hard. Sedimentary rocks are usually in the form of horizontal layers. Did you know that this type of sedimentary rock is still further divided into several types? The types of sedimentary rocks are classified according to several categories. Many experts categorize or classify these rock types with different amounts. Then, what are the types of these sedimentary rocks?
1. According to Pettijohn (1975), O'Dunn and Sill (1986) – divide these sedimentary rocks based on their texture which is divided into two major groups, namely clastic sedimentary rocks and non-clastic sedimentary rocks.
Clastic sedimentary rocks are also called detritus, mechanical, exogenous sedimentary rocks which are sedimentary rocks consisting of clastics or crushed rocks that settle naturally or mechanically by their own gravity. This type of rock is formed as a result of reworking or reworkin from pre-existing rocks. The reworking process that occurs as rock formation includes weathering, erosion, transportation, and also redeposition or re-deposition. To support this process, several media are needed, namely water, wind, ice, and also the effects of gravity or its own weight. Especially for the latter media or this gravitational medium as a result of rock slides that have existed before.What we need to know from this type of rock group is that this rock group is fragmental or consists of grains or rock fragments so that it has a clastic texture. Examples of clastic sedimentary rocks include breccia, conglomerate, sandstone, and slab rock. Breccia is a sharp-angled gravel deposit that is still close to its place of origin. Conglomerate stones are gravel deposits whose corners are rounded (the corners that are far away are carried by the river). While sandstone is sedimentary rock derived from rock fragments measuring 1/16 to 2 millimeters.and also slate. Breccia is a sharp-angled gravel deposit that is still close to its place of origin. Conglomerate stones are gravel deposits whose corners are rounded (the corners that are far away are carried by the river). While sandstone is sedimentary rock derived from rock fragments measuring 1/16 to 2 millimeters.and also slate. Breccia is a sharp-angled gravel deposit that is still close to its place of origin. Conglomerate stones are gravel deposits whose corners are rounded (the corners that are far away are carried by the river). While sandstone is sedimentary rock derived from rock fragments measuring 1/16 to 2 millimeters.
Non-clastic sedimentary rock. Next we will discuss the types of non-clastic rock groups. This non-clastic rock is a type of sedimentary rock that is formed as a result of the evaporation of a solution or the deposition of material that is in the same place. The process of formation of this type of rock can occur by chemical, biological or organic processes, or a combination of the two, namely a combination of chemical and organic or biological. The process which is a combination of the two is called biochemistry. The process of rock formation that occurs biologically or organically is the formation process carried out by certain natural activities, namely by plants and animals. An example of this organic rock formation process is the formation of the home of marine animals or corals,accumulation of animal shells (fossils), and the burial of wood as a result of the land subsidence into the sea.
2. According to Sanders in 1981 and Tucker 1991 - classify or divide these sedimentary rocks into four kinds, namely:
Detritus or clastic sedimentary rock
Chemical sedimentary rocks – Chemical sedimentary rocks are sedimentary rocks that are formed through chemical reactions, such as evaporation, precipitation, and concentration. Examples of these chemical sedimentary rocks are rock salt, gypsum rock, stalactites, and also stalagmites.
Organic sedimentary rocks – These organic sedimentary rocks are also known as sedimentary rocks of bodily origin. Organic sedimentary rock is sedimentary rock derived from the remains of living bodies or made by living organisms. This type of rock group can be broken down into two types, namely biomechanical sediments and biochemical sediments. Biomechanical sediments are deposits of the remains of living body parts that settle naturally under their own weight, for example, limestone, shells, numilites, and layered limestone. While biochemical sedimentary rocks are rocks that occur due to the deposition of limestone and silicium elements with living rocks.Examples of these rocks are limestone reefs or shellfish animal houses and also diatomaceous earth or the deposition of silicon elements due to the presence of carbon dioxide in the water which is absorbed by diatomaceous algae.
Volcanic clastic sedimentary rock. – Especially for this type of rock, it is a sedimentary rock that has a clastic texture with the main constituent materials derived from volcanic activity.
3. According to Graha (1987) – This type of sedimentary rock is a sedimentary rock which is generally non-classical in texture. Graha divides these sedimentary rocks into four groups as well, namely:
- Detritus sedimentary rock (clastic/mechanical)
- Coal sedimentary rock (organic/vegetable)
- Silica sedimentary rock, and
- Carbonate sedimentary rock
Especially for this type of rock and also this silica sedimentary rock can be a clastic sedimentary rock or a non-clastic sedimentary rock. Then based on the composition of the main constituent, clastic sedimentary rocks or clastic textured, can be further divided into three kinds. Namely:
- Siliciclastic sedimentary rock. This type of rock is a type of clastic sedimentary rock whose main constituent minerals are quartz and feldspar.
- Then there are volcanic clastic sedimentary rocks. Volcanic sedimentary rock is one type of sedimentary rock with the main constituent materials derived from volcanic activity, such as glass, crystal, and/or lithic.
- The last one is clastic carbonate sedimentary rock, also known as clastic limestone. This type of rock is a clastic sedimentary rock with the main constituent minerals being carbonate material (calcite).
Those are the types of clastic sedimentary rocks according to their main constituent composition. Next we will discuss the color of sedimentary rocks.
Sedimentary Rock Color
If we generally find that the rock is dark, i.e. black or slightly grayish, then this sedimentary rock has a slightly subdued or light color. This sedimentary rock has a distinctive color. The color of these sedimentary rocks is generally light or bright, such as white, yellow, or light gray. However, this sedimentary rock is not always bright or light in color. These sedimentary rocks have dark colors, namely dark gray to dark black, as well as red and brown. Thus this sedimentary rock has a variety of colors. The color variation of sedimentary rocks is caused by the composition of the constituent materials.
