00:01.18 alan Thank you? Well welcome back everybody we're really blessed and honored to have Andy with us minerad Andre who's a biogeochemist and he's the gentleman who's been pioneering the ah xrf method of dating rock art throughout the world. 00:18.77 Andi Yes I am. 00:18.77 alan And Andy are you with us. So let's ah, open it up in the second segment and get to some of the nuts and bolts people tell us that rock art is nearly impossible to date and they also tell us that. Many of the methods that have been attempted are in fact, controversial and subject to um, some tremendous problems and scrutiny. Do you agree with that or no. 00:48.80 Andi Well, um I think there's a number of methods as you say and I think they have strength and weaknesses I think with any of those methods. It's ah very easy to produce wrong results. Um. But I think they all have have some merit of course brock art. Well some rock art actually contains carbon that one could the Principal use to um. 01:22.64 Andi Make ah carbon 14 age measurements and that is more or less sort of the the gold standard for actually determining ages in the sort of range to which it's applicable to some like 50000 years ah but in order for that to be valid. You have to have carbon which is actually directly connected to the rock art that you're studying and as I say with some kinds of rock art pictographs which are like painted onto rock. Um, there may be organic binders or charcoal that they've been using um and that that can be reasonably well related um to the actual age to the time of creation. So presumably. If somebody has taken for instance, charcoal to draw on on rock and create pictographs that way presumably that charcoal is contemporary with the artist more or less and thus it. Actually would reflect the data of of rock art creation similar things may be said for organic binders. 02:33.90 alan No now what? but right now what? But what writes what we're talking about here for the most part are rock drawings or what we call Petrolyphs and unfortunately when we do rock drawings in Petrolyphs those are lacking in the organics that typically. 02:43.20 Andi Right. 02:52.81 alan Are needed to do any sort of radiocarbon dating. So I guess as as you've pioneered and elsewhere and go ahead. Please go ahead. 02:56.42 Andi Yeah, precisely and I mean some are yeah I mean some petrolyphs ah appear to include some fragments of of organic matter under the newly formed rock varnish. And that has been used but has been also very controversial of Ron Doran took measurements along those lines and there's been a huge ah mess in the literature about ah whether those things were valid or not or all sorts of dark accusations have been made. Um, so ah, but that aside um, the creation of rock art petroglyphs consists in the removal of something and so if you remove something then well that makes it difficult to actually come up with a date and so people have been using. Weathering processes like the rate at which the sharp edges on the on the minerals that are in in behind the rock art so to speak at which those sharp edges become rounded again by by weathering. Ah. And that's been maybe a ah useful method. Um, for in some instances but it's quite difficult to calibrate. Ah, people have been using other approaches such as layering of inside rock barnish that has been newly formed. 04:29.70 Andi And there is a ah gentleman named you who has been using that successfully but the problem with most of those things is that um a they're difficult to calibrate and B many of them require actually removal of samples and that's just not something. That's very popular. In archaeology because you really don't want to um, start scraping away material from this precious rock Art. Oh. 04:54.86 alan Yeah, you don't want to be a just destructive Method. So what? what helps us with your method and and others that's non-destructive is to use some sort of a portable Xrf machine that we can quantitatively measure. The Ah trace elements that exist in the rock varnish am I correct. 05:19.28 Andi Right? Yeah I mean there's this wonderful instrument called the portable x-ray fluorescence analyzer or pxrf and that you can sort of visualize like something like a little bit heavy ah hair dryer. Um, it's got to put the size and shape of ah of a hair dryyer. It weighs a little bit more than that and so that's easily ah, portable into the field. It's ah, battery operated so you can pretty much with a couple of batteries operated for a whole day and. All you really need to do to make a measurement is you take this thing and hold it against whatever we want to measure the rock surface the petrolyph and press the trigger for something like ah 30 seconds so to maybe 2 minutes or so and then you have a measurement. Um, and so it's very easy in within one day or so to make 100 measurements and so that's another great advantage of this method is so you can get a lot of data and with a lot of data. You can do statistics and any error that may be in. Involved in ah in a single measurement um will can be either identified by being a statistical outlier or averaged over if you make ah a whole lot of measurements so that takes. 06:38.32 alan So what? you? So what? What we're what we're measuring and we're looking for is we take our machine and look in the interstices if that's if that's the right word we're looking for a spot where we can get a clean measurement within the glyph itself. Correct. 06:58.11 Andi Right? Yeah I mean you basically the spot size of this instrument is eight millimeters um what's that ah, a third of an inch for those who think in inch units. Um, and you can actually narrow it down to three millimeters but typically. 07:05.42 alan Right. 07:14.29 Andi Best measurements you get with the Eight Millimeter spot size. So all you need to do is basically you look at your ah your rock art element your um antelope or your um, your desert bighorn. That's been depicted and then you find the spot that's at least Eight millimeter in size. And then you make a measurement and what you measure is actually the concentration of Manganese because Manganese are the diagnostic element. Ah for rock varnish and you do this ideally within 3 4 or 5 spots within the same. Rockar same petrolyph the same rockart element and also you make the same kind of measurements in the untouched in the intact. Ah rock varnish that's surrounding your petroglyph and then from the ratio between what you measure on the petroglyph itself. And in the surrounding intact virgin desert varnish rock varnish from that ratio. You can then get an idea as to how long that petarclyph has been sitting there exposed to the formation of fresh new varnish on its surface. 08:28.71 alan So we need we need some means to to calibrate it. Don't we we need some sort of measure to ah understand what that ratio might mean chronologically correct. 08:40.69 Andi Exactly and that's ah the most difficult part really of this whole approach. You need calibration surfaces and as I pointed out before in Saudi Arabia we were very lucky because people may have made these dateable inscriptions. And in North America that's much more difficult because there are there's no writing people have not developed writing there. Native people have not developed writing in North america so we don't have inscriptions that have dateable types of of scripts. But there are other things there are transitions like that from the atlatl and spear to the bow and arrow which happened some two thousand one thousand five hundred two thousand years ago um there are also at other sites ah particular kinds of sandals. That ah, the native americans warned that show up in rock art and those sort of things again. Give you time markers that you can use um to determine the rate of new formation reformation of farnish on the petrlyphs. And thus again develop a measurement of the rate at which varnish accumulates and once you know that rate, um, then you can determine the age of unknown petrolyph surfaces. So. In other words, if you know that. 10:13.11 Andi X amount of of Manganese forms over 1000 years then if you measure 2 or 3 times that amount on a um on a petroglyph you know that it must be about 2 3000 years old 10:26.74 alan Yes, and so we have the the changes in technology. We've got the use of the out Lotl we've got the bow and arrow depicted. We also have some historic cliffs that will give us some sort of contact date and we try to sort of. 10:41.50 Andi Um, right. 10:45.99 alan Look at the superimmposition or the way in which we expect to see the different images and how they are depicted I just I've just published a a little booklet a small book on the depiction of projectile points. 10:55.10 Andi Um, friend. 11:04.19 alan Exist in the Koso rock art and those projectile points are a specific style of rock art and they date to the middle archaic and so we can use those as sort of an anchor as well which it would which would be a further interest certainly because we have some sort of a. 11:12.87 Andi Excuse you. 11:22.67 Andi Um, yeah, yeah, and in fact, on one and the most recent site that I worked on in North America which is in Northern Utah we also used a particular style of projectile point as ah as a time marker. 11:24.21 alan Ah, diagnostic. Yeah um. 11:38.40 Andi So that's quite useful if you have identifiable objects such as projectile points with ah with a specific outline. 11:48.73 alan What? Um, what do you remember? what projectile point form it was and and what the age was generally for that form. 11:55.55 Andi I Can't actually tell you right now off the top of my head that we'd have to look that up. Yeah. 12:01.66 alan Yeah, yeah, I'm going to have to look at that too that would be interesting. Um, it appears that there's a prominence There's only a particular time in prehistory and it seems to be rather consistent that throughout the Americas. Ah. There was what was called a fluorescence and ah in what some researchers call a hunting religion and that just existed in the middle archaic from about 2000 bc to about a d one and um, that's the that's sort of the the dating on many of these. 12:30.72 Andi Is it. 12:39.55 alan Projectile point images. So it's just just interesting to think about and to see how that all ferrets out so you were saying the the odyssey here you began doing this in the Middle East correct 12:53.70 Andi Um, that's right? Yeah um, and. 12:56.48 alan And and and and how did that go? What did you learn? What did you discover?? what? How did this? How was your technique refined and um and how did this this whole research ah position or research project. Develop. 13:15.40 Andi Yeah, um, well I had a collaboration actually with colleagues in in Saudi Arabia before when I was still not really thinking about um, ah, rock art and but I wanted to go to places in in Saudi Arabia where I could surely find good developed desert varnish to make measurements on the geochemical aspects of it. We were also interested in seeing whether we could find any evidence for the involvement of of microbes in the formation of the desert varnish and. So I thought well have not haven't not been in Saudi Arabia before and not really knowing where to go. How can I go to a place where I for sure find the desert varnish and I read some articles about Saudi Arabia and so then I stumbled on. 14:02.91 alan O. 14:10.88 Andi Rock art there I said well yeah I mean that's for sure a place where I find desert varnished because I can see all those pictures of rock art carved into into into desert varnish. So I said okay, well for my first field trip to to Saudi Arabia I just go to this place in the middle of um. Sort of central Saudi Arabia where all these pictures were made showing rock art surrounded by good rock vaish then I went there and was just. Totally fascinated by what I actually saw in in the rock art. There were some scenes where you saw men in lines sort of dancing. There were other scenes where you saw lots of camels so there were um. 15:04.72 Andi Various kinds of of animals a kind of a goat species and that's it's that's very abundant there and I I said well maybe I should actually focus more on the rock art And. Ah, was as I've mentioned before it's kind of hopeful that the archaeologists would be able to tell me ages of this rock art I saw that the the guys that were dancing they were covered with a varnish that was almost completely as stark as the surroundings and the camels were a lot. 15:30.20 alan Ah. 15:41.54 alan Um, oh wow. 15:43.33 Andi Lighter colored and some of the the eyebexes this wild desert goat sort of seemed to range all through the different kinds of of frack barnish sickness. So suggesting that. People have been depicting ibexes from the pre-neolithic basically up to yesterday and sort of in a similar way like you see pickhorn cheap in in North America which also go from the beginning of the holocene ten thousand years ago to very very recent. So. That's 1 thing as an aside that people apparently like to depict these sort of these sort of game animals. Fancy game animals anywhere in the world. You see fancy game animals depicted in the ah rock art in North of most Scandinavia. Way north of the polar circle anyway I was just fascinated by by the rock art and then decided to actually make a project out of it. Um, yeah, ah. 16:48.59 alan Let's let's hold it there and we'll pick it up on the next segment. Thanks Gang see in the flip flop.