Among the geological formations found on our planet are cratons . The term craton is used to distinguish the stable internal portion of the continental crust from orogenic regions, which are linear belts of sediment accumulation and/or erosion subject to subsidence and/or uplift.
In this article we are going to tell you everything you need to know about craton, its characteristics and importance.
Continental crust
The continental crust is very old and eroded, containing ancient igneous and metamorphic rocks. Post-Archaean rocks retain a folded overburden of more or less metamorphic sedimentary rocks. The former are found in flat, almost flat, terrain, while the latter form mountains. A craton or cratogen (from the Greek kraton, meaning very flat bowl) is a landmass that has reached such a rigid state in the distant geological history that it has not undergone fragmentation or deformation because it has not been affected by orogenic movement. For this reason, cratons tend to be flat or have rounded low reliefs and are usually composed of ancient rocks. Submarine cratons are called neocratons.
What is a craton
The term craton is used to distinguish the stable interior parts of the continental crust from orogenic belts (continental margins, sedimentary basins, and orogenic basins), which are linear accumulations and/or zones of sedimentary erosion (basins) subject to subsidence and/or uplift (mountains). The broad central craton of the continent may be composed of shields and terrestrial platforms , as well as glacial bases. The shield is part of the craton, where Precambrian rocks are widely exposed at the surface. In contrast, the basal platform is covered by horizontal sedimentary deposits and sublevels.
The shield is a continental area composed of rocks that were formed in the Precambrian period, which were not covered by the sea. The shield is formed by the oldest rocks of the earth's crust, granitization and metamorphism. Since their origins, they have been stable and maintain their rigidity.
The fact that they have never been submerged by transgression is due to their having undergone vertical tectonic movements. They did not experience folding because they resisted all horizontal thrusts. Shields are generally igneous and metamorphic rocks exposed over a large area, with stable structures and little orogenic activity. In all cases, these rocks are over 570 million years old, and some date back 200 to 3,5 billion years.
Due to its stability, erosion flattens the topography of most continental shields. However, they generally have fairly convex surfaces and can be surrounded by sediment-covered areas called continental shelves. Bare areas, covered platforms and crystalline bases together constitute a stable part of the continental crust that constitutes the shield or craton.
Shields and their importance
The shield is usually the core of the continent, and most of it is bounded by a folded Cambrian belt of rocks. These bands were welded to the edge of the pre-existing earth shield, thus increasing the size of the original continent they formed. The edges of the shield are affected by the tectonic force, which in turn destroys and rebuilds them, as well as the craton in which they are located.
A craton is a large structural unit of the Earth's crust, composed of a large amount of stable rock, usually igneous and/or metamorphic. It is sometimes covered by thin layers of sediment. A typical craton is the Canadian Shield (Precambrian). Land parcels called "oceanic" or "submarine" cratons may not meet this definition. "Craton" is actually a synonym for shield.
A craton is a stable part of the continent's interior, characterized by its composition of ancient crystalline basement rocks. The term craton is used to distinguish these areas from mobile trenches, which are linear belts of deposited sediments. The vast central craton of the continent can be composed of two things: a shield and a platform. The shield is part of the craton, where (generally) the Precambrian basement rocks are widely exposed at the surface. In contrast, on the platform, the basement level is overlain by sediments.
Cratons of Paraguay
The craton consists of a very old core. Given its mobile nature, these cores merge to form a continent. However, they do not always appear on the surface. Paraguay has the Apa Craton (from the north) and the Tebicuary Craton (from the south). Beneath the Chaco region lies the Pampia Craton, which is separated from the RĂo de la Plata and the La Plata Craton.
The Transbrasiliano Lineamiento is a zone of suture, of union, of continental collision where the cratons are united, and it has continuity until West Africa, passing through the Brazilian territory. This first-order structure, as a suture, dates from the Lower Cambrian (528 million years) when Gondwana was formed.
There are controversies if the Tebicuary River craton belongs to the RĂo de la Plata or not, or if the Paraná (below the Paraná basin) is a different block from the RĂo de la Plata. However, the most widely accepted model is presented here.
Differences between craton, basin and fault
A craton is a stable area of ​​continental crust that has not experienced much orogenic or plate tectonics for a long time. A craton consists of a crystalline base of Precambrian rock, commonly called a shield, and a platform upon which horizontal or nearly horizontal sedimentary rocks surround the shield.
Basins are depressions in the Earth's crust formed by plate tectonics , where sediments accumulate. Continued deposition leads to further pitting or subsidence. Sedimentary basins, or basins for short, can be barrel-shaped or elongated. If hydrocarbon-rich source rocks combine under sufficient burial conditions and time, oil and gas can be produced in the basin.
Finally, a fault is a break or sheet-like surface in a brittle rock along which there is observable displacement . Depending on the relative direction of displacement between the rocks, or fault blocks, on either side of the fault, its movement is described as direct (or normal), reverse, or strike-slip.
I hope that with this information you can learn more about the craton and its characteristics.