Conglomerate, rarely psefit, is a term for the consolidated equivalent of gravel. This name applies only to rocks with a predominance of worked (rounded) fragments larger than 2 mm, the name breccia is usually used for sharp-edged fragmentary sedimentary rocks.
The term conglomerate was introduced in 1835 by Ch. Lyell.
Conglomerates are composed of layers of older rocks, primary softer material that fills the gaps (matrix) - mostly sand or clay and chemically precipitated cement (sealant). Facies larger than 2 mm should make up more than half of the rock. If the individual forms do not touch each other (they are loosely laid in it and covered by the base material), they are usually poorly processed (structurally immature). Ripe agglomerates contain a small amount of ground material and are usually well sorted (with the individual layers touching each other).
Cement is usually calcite, siliceous, ferruginous in arid environments. Its composition depends on the chemical composition of the solutions circulating in the sediment. In the case where the base material predominates in the agglomerates, individual forms are often coated with clay.
Conglomerates are not a homogeneous group of sediments, they are divided based on several criteria (according to the place of deposit, according to the chemical composition of the cement, according to the petrographic description of fragments, structure). The division also applies to gravels and breccias.
According to the origin of the fragments
According to the origin of fragments, agglomerates are divided into:
- epiclastic conglomerates - fragments come from weathering processes
- pyroclastic conglomerates - formed during the deposition of volcanic products
- cataclastic conglomerates - arise during tectonic movements of the earth's crust (landslides, slides, collapses). Sharp-edged fragments - breccias - predominate in this group
- impact breccias - arise as a result of meteoritic impacts.
If conglomerates are formed from layers of the same rock composition, they are called monomictic. Polymictic conglomerates have layers of diverse composition. In the event that two-three or only a few rock types prevail in the formations, the term oligomictic can be used.
The study of the petrographic composition of conglomerate formations makes it possible to conclude about the original material of the conglomerates, the conditions of formation, the method of transfer and formation, the direction of sediment transport in the past and other important factors. An example is the expansion of clayey rock deposits, which are not resistant and indicate a short transport of sediment in conglomerates. The appearance of rock formations, which are no longer present in the area where the conglomerates were formed, is proof that its source area was completely eroded.
According to the place of sedimentation
According to the place of lithification (hardening) of the sediment, agglomerates are divided into:
• intraformational agglomerates - formed by the disturbance and subsequent consolidation of already existing sediments directly in the place of the sedimentation pool. Such processes most often occur below the surface (sea, lake). Individual fragments are mostly not processed, as their transport is minimal, they are often referred to as intraformational breccias. This group of agglomerates is not very widespread.
• extraformation conglomerates - it is the most important part of conglomerates. They are formed by weathering and the subsequent transport of weathered material to the place of sedimentation.
By structure
• orthoglues - their internal structure is formed by contacts of forms and coarser grains. It does not contain clay-sized grains, or only trace amounts.
• paraclastics are conglomerates that contain more fine-grained material than coarse fragments (individual forms are chaotically distributed in the basic mass). Such sediments mostly come from a terrigenous (terrigenous) environment (whether different mudflows or sediments of glacial origin - tillites).
During the ascent to the pyramid, we have various opportunities to observe the exposed blocks on the pyramid. Where we can see different sizes and forms of agglomerates.
Bosnian pyramid of the Sun
With its height of over 270 meters, it is the tallest pyramid in the world. It has a regular pyramid geometry with three preserved sides: north, east and west. It is lined with rectangular blocks. According to the Institute of Materials from Bosnia and Herzegovina (2006-2008) and the Politecnico di Torino from Italy (2009), the blocks are made of the highest quality concrete material superior to modern concrete. In fact, the attitude towards pyramids varies. Some consider it a pyramid, some consider it a natural creation. It depends on who researched it and who financed it. When you explore a place, you can form your own opinion as to whether it is natural or artificial.
Your task will be:
1. Observe the clumps along the road and guess what type of clump it is based on the sedimentation.
2. What type is it according to the structure?
3. Compare the clumps found on the way to the castle and the stones from which the castle is built. Are they of the same nature or different?
4. Consider the fact that it is not concrete as they were created and got to the places where they are now.
5. Do you think it is agglomerate or mechanical concrete?
6. Photo from the place or from the way to the top of the pyramid from an interesting place.
Source/ photos: Wikipedia, own photos and studing place