Among the geological formations that we find on our planet we have the craton. The term craton is used to distinguish the stable inner portion of the continental crust from those orogenic regions, which are linear belts of accumulation and / or erosion of sediments 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-Archean rocks retain a folded overburden of more or less metamorphic sedimentary rocks. The former are found in flat, almost flat terrain, and the latter are mountains. Craton or cratogen (from the Greek Kraton, meaning very flat bowl) it is a land mass that has reached such a harsh state in distant geological history. Since then, it has not suffered fragmentation or deformation because it has not been affected by the orogenic movement. For this reason, cratons tend to be flat, or have round bas-reliefs, and are usually ancient rocks. The underwater craton is called nesocratons.
What is a craton
The term craton is used to distinguish stable internal parts of the continental crust from orogenic belts (continental margins, sediments and orogenic basins), which are linear accumulations and / or zones of sediment erosion (basins) subject to subsidence. And / or uplifts (mountains). The broad central craton of the continent can be composed of shields and ground platforms, as well as glass bases. The shield is part of the craton, in which Precambrian rocks are widely found on the surface. In contrast, the base platform is covered by horizontal sediments 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 for transgression is due to the fact that they have suffered 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 few orogenic activities. In all cases, these rocks are more than 570 million years old, and some date back 200 to 3,5 billion years ago.
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 larger structural unit of the earth's crust, made up of a large number of stable rocks, generally igneous and / or metamorphic rocks. Sometimes covered by small sediments. A typical craton is the Canadian Shield (Precambrian). Parcels of land called "oceanic" or "underwater" cratons may not meet this definition. "Craton" is actually a synonym for shield.
The craton is a stable part of the interior of the continent, characterized by being composed of ancient crystalline basement rocks. The term craton is used to distinguish these areas from moving trenches, which are linear belts of deposited sediments. The huge central craton of the continent can be made up of two things: an earth shield and a platform. The shield is part of the craton, in which (generally) the rocks of the Precambrian basement are widely exposed on the surface. In contrast, on the platform, the basement or sublevel level is overlaid by sediment.
Cratons of Paraguay
The craton consists of a very old nucleus. Given their mobile nature, they merge to form a continent. However, they do not always appear on the surface. Paraguay has the Apa Craton river (from the north) and Tebicuary (from the south). Below the Chaco is the «Pampia» Craton, which it is separated from the Río de la Plata and the Craton de La Plata.
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 Río de la Plata or not, or if the Paraná (below the Paraná basin) is a different block from the Río de la Plata. However, the most widely accepted model is presented here.
Differences between craton, basin and fault
The craton is a stable area of the continental crust and has not experienced much orogenic tectonics or plates for a long time. The craton consists of a crystalline base of Precambrian rock commonly called the shield and a platform on which horizontal or near-horizontal sediments or sedimentary rocks surround the shield.
The basins are depressions in the crust formed by plate tectonic activity, where sediments accumulate. The persistence of the deposition will produce an additional degree of pitting or subsidence. Sedimentary basins, or basins for short, can be barrel-shaped or elongated well. If the enriched hydrocarbon source rocks are combined under conditions of sufficient time and depth of burial, oil and gas can be produced in the basin.
Lastly, the fault is a interruption or laminar surface existing in brittle rock along which there is an observable displacement. Depending on the relative direction of displacement between the rocks, or fault blocks, on both sides of the fault, their movement is described as direct (or normal), reverse, or course displacement.
I hope that with this information you can learn more about the craton and its characteristics.