That much I understood but where I was uncertain was getting different carbon dates for different parts of the tree. I assumed the item would give one date overall. I’m still not sure if I’m right about that but if so then it makes sense.
Ahhhh... well in that case the younger date could have come from fungus or spores that may have grown on the old log if it became partially exposed at some point or an air pocket became trapped under it. The growth would have died away a long time ago but left biological material causing C-14 ratio-contamination between cracks in the much older log — that’s just one example.