At least one of those marks looks like a recognisable rune. (At least I think so. it's been a goodly while since I dabbled in suchlike).

I think the likelyhood of a crossed gate type motif occurring by chance must be pretty small.

Its hard to see from the tiny picture - id appreciate a full resolution one if you could send me a jpeg ? But from what I can see, the mark shaped like 'R' is visible and this is usually associated with travel, journey or a passage. This could be a reference to the passage of the spirit into the next world or literally a waypoint for a traveller on the road. The lichen appears to cover the incisions, so it doesnt look recent. Earthstepper will probably know best.