I'm not sure this is a marker. Their looks like a face looking at a somewhat heart which would mean keep going until you find a rock shaped like a heart and that is where the Gold will be. In a situation like this I would do just that start looking for a rock carved heart in that location you should start finding other signs like a turtle if not then it is natural erosion.
I wonder about that face's eye. If it looks drilled well i saw an interesting pic elsewhere on the net, with two large drill holes right near a bricked up tunnel or cave entrance. That person stuck a couple of large sticks in them to find directions.
Might be worth a look around to see if something like is occurring here.
I can only tell what I see, Knight with Helmet, Spaniard also with helmet, small elephant head with ears, a Great Shield at bottom front, and in the center The King with a Gold Corona or Crown. I think so, Royal Trail TD
I would investigate the area the eye is looking at very well and to know for sure where it is looking I might put a strait stick in that eye. I did not think any thing when I first looked at the face but their are things there that look man made so it wouldn't hurt to take a look.