In a thread posted on this yesterday or Friday, we had a long & interesting discussion. (At least I was interested, since I studied archaeology while I was an undergraduate.)
In much of Northern England, the combination of highly acidic soil and VERY damp ground means that folks just decompose into nothing. When archaeologists are excavating prehistoric burial mounds, you shave off paper-thin layers of soil in likely burial areas, because nothing will be left but what they call "corpse shadows" - slight difference in coloration in the soil where the bones reacted with the soil as they decomposed. It looks pretty much like an X-ray.
Surprised that there was much of the wooden coffin left. Even the metal coffin-plate was in very rough condition.
So even the bones and teeth go?