Answer:
Downwarping known as a basin
Explanation:
Under the Principle of Original Horizontality, sediments are always deposited in horizontal beds. Any bed that is found to be tilted has undergone a geological transformation. The Principle of Superposition states that the younger beds are always found overlaying older beds. In a horizontal sequence, the youngest rocks will always be at the top.
Upwarpings, or domes, are uplifts of the ground caused by tectonic deformation. Because domes are spherical or ellipsoidal protrusions on the Earth's surface, the younger rocks are said to be on the periphery, whereas the oldest rocks are in the centre.
In a downwarping, or basin, the deformation of the ground produces a concavity. Whereas in an upwarping we have one point of uplift, in a downwarping we have two points of uplifting (in a tectonic deformation, product of subduction such as the Chilean Central Valley), or one point pushing down because of isostacy (such as the Hawaiian Through). In these basins, the youngest rocks stay near the centre of the concavity (or inside).
Horsts occur when two main faults push a fragment of the crust upwards, and the adjacent fragments downwards (these two fragments are then called grabens). In a flat undeformed ground, the horst keeps the youngest rocks on top. If the fault system develops in either a dome or a basin, then the position of the older and younger rocks is determined by the position they had after the deformation of the ground.
Finally, in a fold and thrust mountain belt, such as the Pyrenees, the ground is deformed due to the collision of two continental tectonic plates, producing a system of faults, synclines and anticlines. In general, younger rocks remain in the surface, but the new generated system of faults can put older rocks on top of younger ones.
