At "our" lake, Fairhaven, a few years ago we persuaded the council to extend the paved launching area. Old (30 years ago) pictures show the grassed area from the park path to the lake side as being level, but to pave it the grassed area had to be dug down to a depth of about 15". Looking at the small cliff thus formed, strata were visible - dark, sand, dark, sand. I took the dark to be the result of guano-assisted plant life of summer, and the sand as, well, sand, having been blown in from the Ribble estuary over the winter and trapped by the grass. Presumably the sand was scenery worn away from somewhere else, deposited on the beach and subsequently blown back onto land. This sort of thing could go on world wide.
The old artifacts are not really sinking, everything else is building up.