That rock is certainly shaped and smoothed over the edges and that does look like a turtle. Are there any other large rocks, boulders, and / or stones in the area? The only way to investigate this rock is to follow the compass heading indicated by the "head" of the turtle and see what you find. Look for other signs and symbols along that heading. IF there are any, they could be almost any distance from this rock; a few yards to a few miles. If this is a symbol rock along a trail, the next symbols / monument will probably be less than a mile.
Good luck. Hope this is a trail sign that you can investigate. At the LEAST, it is an interesting find as a rockhounder. Just please don't move the rock; just in case it IS a trail marker.
Cool rock.
Are there any other outstanding things within 100 feet of it?
Check in all directions and make sure that there are no ther rocks stumps trees
or other natural things placed in unnatural places or positions.
If there are no other questionable things in the area,
It is still a cool rock.