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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 collision of this oceanic material causes crustal thickening and mountain-building. The accreted material is often referred to as an accretionary wedge or prism. These accretionary wedges can be associated with ophiolites (uplifted ocean crust consisting of sediments, pillow basalts, sheeted dykes, gabbro, and peridotite). [75]
Accretionary margins, such as the southern Peru-Chile, Cascadia, and Aleutians, are associated with moderately to heavily sedimented trenches. As the slab subducts, sediments are "bulldozed" onto the edge of the overriding plate, producing an accretionary wedge or accretionary prism. This builds the overriding plate outwards.
The formation of a forearc basin is often created by the vertical growth of an accretionary wedge that acts as a linear dam, parallel to the volcanic arc, creating a depression in which sediments can accumulate. [45] [46] [47]
The result of these feedbacks is the stable angle of the wedge known as the critical taper. When natural processes (such as erosion, or an increase in load on the wedge due to emplacement of a sea or ice cap) change the shape of the wedge, the wedge will react by internally deforming to return to a critically tapered wedge shape. The critical ...
The western boundary of this basin was created by the growth and uplift of an accretionary wedge consisting of sedimentary, volcanic and metamorphic rocks scraped off the subducting plate. The uplift of this accretionary wedge acted like a dam to form the western side of a basin in which the Great Valley Sequence was deposited.