"Oceanic plates" are large sections of the Earth's crust that make up the floor of the oceans. They move and interact with each other, which can lead to the formation of features like underwater mountains and trenches. Full definition
The findings might apply to other oceanic plates as well. (sciencedaily.com)
Sediments from the Triassic in the deeper ocean have been mainly subsumed by subduction of oceanic plates, leaving but a sparse marine fossil record. (fossilmuseum.net)
Since, if I remember correctly, subduction generally occurs when a dense oceanic plate dives under a less dense continental plate, you'd have to get the waste to the seafloor and then bury it there in such a way that it wouldn't leak into the water before it sank deep enough into the Earth to be safely forgotten about. (realclimate.org)