A
foreland basin is a
structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by
crustal thickening associated with the evolution of a mountain belt causes the
lithosphere to bend, by a process known as
lithospheric flexure. The width and depth of the foreland basin is determined by the
flexural rigidity of the underlying lithosphere, and the characteristics of the mountain belt. The foreland basin receives
sediment that is eroded off the adjacent mountain belt, filling with thick sedimentary successions that thin away from the mountain belt. Foreland basins represent an endmember basin type, the other being rift basins. Space for sediments, accommodation space, is provided by loading and downflexure to form foreland basins, in contrast to
rift basins, where accommodation space is generated by lithospheric extension.