[AlexW]

“Dating rocks can be a little tricky.”
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I’ll say......How on Earth can they determine the age of the carvings without a reference point?

[Rebel_Ace]

"....How on Earth can they determine the age of the carvings without a reference point?"

Actually, there would be two datapoints to look at with the carved rock.

(1) You could measure the external "oxidation" or other weathering effects on the UNCARVED area of the rock.

(2) You then measure the "oxidation" or other weathering effects on the CARVED area of the rock, and compare the two.

Since the carvings on the rock must be younger than the rock itself, the carvings would expose FRESH, UNWEATHERED rock to begin "oxidizing", you should be able to see what the difference is, and from other chemical experimental data, give an educated estimate for the time it would take to deposit that much weathering on the carved surfaces.

A real world example might be an old home with wooden trim that has been painted many times by previous occupants.

You see some wooden moulding with deep gouges in it. On the major surfaces of the wood, you strip away 8 layers of paint. In the areas with the gouges, you strip away only 3 layers of paint.

From data you gather elsewhere, you have learned that the average family repaints a room every 15 years.

3 Layers of paint in the gouges means that a 45-60 year guess for when the gouges occurred is reasonable, and backed up by testable evidence.