Sea floor sediment and oceanic crust pieces are scraped off a subducting plate and accumulate in the complex.

subduction

Explanation:As a result, off the coast of the continental crust a trench will form pointing out the subduction zone and oceanic sediments will be scraped off the subducting plate to form the accretionary wedge. ...

During that subduction process ocean sediments would have accumulated along the trench forming an accretionary wedge.

Furthermore,

Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to high gravitational potential energy into the mantle.

i r r e l e v a n t

answer; rarely listen to the child's point of view;