Can you see the marks? 

Here is the same photo with the marks outlined. Compare the 2 photos carefully. You'll notice there are few hills of this size in the area, so the marks are not being selected to fit in the theory.
Look where each dot is and compare it to the photo above, to get an idea what these marks look like.
Drawing the lines through the dots makes six right angled triangles pointing directly at the center of the face mouth. Check the angles yourself to confirm the accuracy. Note how the line goes through the small rectangular shape. These are quite common and always go along one of these lines.