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An accretionary wedge or accretionary prism forms from sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust , but in some cases the wedge includes the erosional products of ...
Oceanic-continental convergence and creation of accretionary wedge Stages of accretion through time with accretionary wedge and volcanic island arc. In geology, accretion is a process by which material is added to a tectonic plate at a subduction zone, frequently on the edge of existing continental landmasses.
Basin depth depends on the supply of oceanic plate sediments, continentally derived clastic material and orthogonal convergence rates. [1] [2] The accretionary flux (sediment supply in and out) also determines the rate at which the sedimentation wedges grow within the forearc. [1]
The first is by frontal accretion, in which sediments are scraped off the downgoing plate and emplaced at the front of the accretionary prism. [2] As the accretionary wedge grows, older sediments further from the trench become increasingly lithified, and faults and other structural features are steepened by rotation towards the trench. [27]
Accretionary wedges in front of subduction zones are normally covered by oceans and the weight of the seawater on top of the wedge can be significant. The load of the water column is the hydrostatic pressure of the water column, multiplied by a factor α + β {\displaystyle \alpha +\beta } (the angle between the top of the wedge and the base of ...
Smaller 'trench slope basins' can form in association with a trench can form directly atop the associated accretionary prism as it grows and changes shape creating ponded basins. [53] [54] Trench fill sedimentary basin in the context of a convergent plate boundary: Middle America Trench [55] Western edge of Vancouver Island; Aleutian Trench ...
An accretionary prism or accretionary wedge is formed from sediments that are accreted onto the non-subducting tectonic plate at a convergent plate boundary.Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust but in some cases includes the erosional products of volcanic island arcs formed on the overriding plate.
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.