I've just watched a program by Bettany Hughes, "Treasures of the World" Ser 2 Ep 1 where she shows rock art and graffiti, from the neolithic onwards found on the Hisma plateau, Saudi Arabia.

What immediatly struck me was the stark contrast between the colour of the rock and the engravings.  They look very fresh.  The rock is a sandstone weathered to a dark colour.  The engravings are the colour of sandstone, freshly broken.

As a contrast, she showed one of a 4X4 done by a Bedouin which looked more weathered than the 'ancient' markings.


Any ideas or comments, very much appreciated.

I haven't seen the program but I guess you are referring to these sort of graffiti which include both recent and ancient inscriptions side by side (this pic is taken from saudiarabiatouristguide.com and I chose that particular image as there are - apparently so, I'm no expert - neolithic depictions of antelope and ostriches at upper left, with a slightly-more brightly-carved 4x4 car with its obvious round wheels, scratched at bottom right):



I don't really know ... however I assume that the area has been arid for a very long time and still receives very little rainfall and thus the rocks and carvings do not actually weather much at all, although obviously they acquire a dark patina (from oxidation or other surface chemical reactions) over very long time. Accordingly the graffiti, whether done just a few years ago, or several millenia ago, are all still 'recent' enough in a geologic sense to have simply scratched through the very old dark-coloured surface patina and exposed the lighter-coloured underlying rock, no?

PS : A quick look online suggests that geologically the sandstone rock formation is an inselberg, meaning it has existed as an exposed isolated craggy escarpment for many millions of years and certainly considerably longer (by an order of thousands) than the 10, 000 years age of the earliest carvings, made when the rocky outcrop overlooked a shallow lake surrounded by grasslands with grazing animal herds.

Hi Meles
Yes.  You are correct on all counts.
The ones in the photo are what I am asking about, and they look as though they have some age to them. The ones in the program looked like they had only been done yesterday.
Clever use of light/filters or "Refreshed" to make them stand out?  Very naughty if so.

You would think that for a country literally sitting on many tonnes/barrels/dollars worth of hydrocarbons hidden away in its rocks, the geology of Saudi Arabia would be very well understood - albeit that much of the detailed information might be buried in confidential company reports and pay-to-view academic papers - nevertheless my quick search online yielded very little about the surface geology of the Khasm Al-Asmar and Khasm Musayqirah petroglyphic sites. As they both have UNESCO listed status I was quite surprised about this general lack of background information.

IamFof wrote:

Clever use of light/filters or "Refreshed" to make them stand out?

Yes indeed ... short-wavelength (blueish) lighting and clever filters can often make a picture more contrasty, rugged, grainy, grittier and generally more ancient than the reality. That at least is what I say to console the rough-looking elderly man who forlornly stares out at me every morning from the bathroom mirror. I don't recognise him and while "refreshed" isn't the word that most readily comes to mind, I have to admit he does look vaguely familiar.

And is that a 'possum as your avatar? Marsupials are certainly cute but I'm more of a mustelid man myself.

I know the feeling.
Yes it is a Brushtail Possum which regularly visited to have a gorge.
The face, the stance shouts out to me "What you lookin' at mush?"
I would never have guessed about you, but for the fine image of Brock.