Seems that Mars is like the Earth. Both follow Sods Law of Ground Investigation. That's the one that ensures e.g. the only lump of wood in your peat core will be in the middle of the period you're interested in.
Seems that Mars is like the Earth. Both follow Sods Law of Ground Investigation. That's the one that ensures e.g. the only lump of wood in your peat core will be in the middle of the period you're interested in.