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Sedimentary Basins

Sunday 1 January 2017, by Imeru Alfonzo Hernandez

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Sedimentary Basins

The most modern theories consider the origin and location of the sedimentary basins with respect to the tectonic framework where they are found. According to this the location of the basins can be described in reference to three fundamental factors: Type of lithosphere that makes up the basement of the basin, Proximity of the basin to a plate limit and Type of structural deformation predominant in said plate limit .

Basins can be described according to the following tectonic frameworks:

1. OCEAN BASINS: Its base is oceanic crust. Here the proximity to the dorsal (minimum sedimentation rates, mainly siliceous and calcareous muds) or the continental margin (important clastic and non-clastic contributions) will govern the sedimentation.

2. SEPARATE CONTINENTAL MARGINS (RIFTING): Here the sedimentation will be governed by the evolution of the rift process. In the first stage the crust rises and over it appear volcanoes that erupt alkaline lavas. These surveys are very important sources of sediments (such as the so-called red layers, sandstones and conglomerates). When the crust begins to fracture, these sediments interstratify with volcanic flows and when the area invades the sea, proto-oceanic gulfs form. In these gulfs the circulation is restricted and therefore organic matter can accumulate (black shales, hydrocarbon mothers), if the climate is arid, evaporites can also be formed. In this stage the subaerial volcanism is null. There comes a time when the continental crust has decreased its thickness and becomes similar to the oceanic, appearing a dorsal or center of expansion. Two passive margins are then generated, which receive the sedimentary contributions from the continental blocks, generating a basal prism or clastic wedge, which covers the deposited sequences, forming a continental shelf. If the clastic sedimentation is very large (fed by large rivers), up to 18 km thick terraces of clastic sediments and shallow marine carbonates can be generated. In areas of low clastic contribution, the sedimentation will be governed by reef limestones and evaporites (arid climates).

3. ARC - TRENCH SYSTEMS: Here crust is destroyed and volcanic - plutonic arcs are generated that are important sources of sediments. In addition there is the creation of a subduction complex or accretion prism. Likewise, between the generated arcs, the formation of sedimentary basins is possible. The location of ophiolites is also important here.

4. SUTURE BELTS: Where two continental blocks are juxtaposed. When the two continents collide, the sequences of the aforementioned basins are deformed and can be destroyed. Likewise, a characteristic basin called Peripheral is created.

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