Dear Dr. Garfinkel

I have dealt with carvings in rocks but not from the archeologist´s point of view who I feel at the very end has the final say as to what period of painting and carving the petroglyphs pertain to. This is especially true when no anthropogenic "mineral" matter has been preserved. I always tried to get a picture as accurate as possible of the human material (ochre, smelting residues) using trace element, including REE and then I attempted to find a quarrying or smelting site where you can date the processing or mining of the material. I am not sure if the portable XRF is able to the deliver data as precise as necessary as to the trace element content. I am not a specialist in magnetometry but Fe minerals may offer a clue to date the artifacts. It will certianly end up in a trial and error operation. There is no technical blueprint in my opinion suitable for each and every rock painting.

Good luck !

Harald G. Dill

Harold,

Thanks for your insightful answer.  

Best,

Dr. Alan Garfinkel

http://www.dralangarfinkel.com

Alan,

There's a session on academia.edu that may be of interest:

https://www.academia.edu/s/d87624f6ad

Based on my research, there is no one method for dating petroglyphs that can be applied globally.  In the case of the panels I've studied in Ireland and the UK, knowing what the motifs depict, can help immensely in dating both the panels and the sites/monuments where they are found. 

 By searching  the available current literature on this interesting subject and looking  for the specific answers to the questions you are asking for ;  the conclusions are :   The accurate `absolute ` Petroglyph dating method chosen , first needs to be `individualized to the petroglyph to   be analyzed  ` depending on the structure of the  material the petroglyph is created , presence and  accumulation of  Carbon  or other organic material like `Algal tufa samples` on the surface timely fashion   as well as the location of the petroglyph  .  

    Radiocarbon(Carbon isotope analysis by  dating the accumulated carbonate(C isotope)  deposits or the samples of organic matter and rock varnish by Accelerator Mass Spectrometry   ,  X ray fluorescence spectrometry and   digitized colorimetry to achieve seriation dating of ferromanganese patina  are the  three  techniques mentioned in the literature below .  

http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1787&context=usgsstaffpub

http://www.ifrao.com/wp-content/uploads/2014/08/27-2-BednarikAgra.pdf

http://www.ifrao.com/wp-content/uploads/2014/08/26-1-Colorimetry.pdf

http://www.sciencedaily.com/releases/2013/08/130813121622.htm

https://www.scahome.org/publications/proceedings/Proceedings.09Whitley.pdf

We have attempted using XRF and cross checking it with other independent means.  It seems to work out for desert varnish dating of petroglyphs.

Alan: I have a session on ResearchGate.net and Academia.edu which may interest you. One problem is the cost of AMS dates. Bryan.

Bryan,

I included the link to your session on academia.edu in my earlier post.

Dear all, the cost of AMS is not as much as limitation of desert varnish dating.  Carbon content in the material is very low and although nowadays we have tools for doing samples that contain as little as tens of micrograms of carbon, I do not know anyone who tried to do this again after publication in Science 1998 that was led by Beck et al., Perhaps it is time to try again. Best, Irka

Andy Gleadow just gave a wonderful talk on this subject.  Not sure how much they've published yet, but they're using (and actively developing) a wealth of techniques to date rock art in the Kimberley region of Western Australia.

 I believe this is fission track what he applies. Did he show any C14 ages? It would be interesting to see that. Best, Irka

Well said, Alicia: Each pictograph or petroglyph must be evaluated for possible dating on its own merits. I chose micro-stratigraphy because most people can do it with very simple equipment. Bryan.

   The technique  that  Colorado University Boulder Researcher  Geochemist  Larry Benson had used for the age determination of Boulder Petroglyphs * created over limestone rock is Accelerator Mass Spectrometry  measurement of C14 isotope  ratio  from the  carbonate crusts over the petroglyphs ( the color of the rock was darker than the later accumulated carbonate crust so he can take carbonate  samples )  ...

    The radiocarbon dates on the samples indicated the carbonate layer underlying the petroglyphs dated to roughly 14,800 ago. - 

  Carbonate  C14 isotope  ( Which is constantly created by  bombardment of  N14  by cosmic radiation over millions of years  and relatively constant rate of formation in the atmosphere )   is converted to Carbonate CO3   ( in which  C14 isotope` comes from atmosphere ) .

  At the boulder petroglyphs the sample abrasion process did not always reach the inner (oldest) part of the carbonate crust, but they collected 6 samples  and radio carbon dated the samples  with Accelerator Mass Spectrometry . The problem is the  Each and every Crust sample is the end result of `layer by layer` \ molecule by molecule  accumulation of carbonate over the  freshly carved Petroglyph  rock  surface . In other words  Recent and the oldest  all mixed up together  at the crust sample. What we are interested is the  inner(oldest) molecules  and the oldest  `INNERMOST LAYER`  layer  should be  chosen   for  the dating sample  .

 After this information above   theoretically speaking :  IF   ``the  ` FIRST LAYER`   or  BASAL LAYER  OF CARBONATE  FORMATION   on the FRESHLY CREATED  PETROGLYPHS  thousands of years ago  by the  absorption   of C14 isotope containing CO2 from the atmosphere`as  Carbonate salt` over millennium``   CAN BE SAMPLED  AND  MEASURED  ‘',  `differentially`   as the oldest  bottom  layer  over the  bed rock   , which should be the   LAYER OF  C14  ISOTOPE CONTAINING CARBONATE  MOLECULES  OVER THE  BED ROCK  STRUCTURE  - the marginal line is  differentiated by ` color difference` of bed rock and newly formed carbonate crust sample -. Than this  BASAL(Innermost) LAYER  OF CARBONATE  accumulation over the   petroglyph  ROCK  could be the most accurate dating of  Petroglyphs` age  rather than measuring entire crust samples  .

 In other words initial Carbonate layer  which occurs  immediately  over the `freshly created  rock surface` ..

Generally  Acid Hydrolysis of Carbonates  CO2 generation than conversion of CO2 to Graphite (Graphitization)  is used for sample preparation for the Accelerated Mass Spectrometry

* http://www.colorado.edu/news/releases/2013/08/13/new-cu-boulder-led-research-effort-dates-oldest-petroglyphs-known-north

http://rockartblog.blogspot.no/2014_01_01_archive.html

http://www.radiocarbon.com/accelerator-mass-spectrometry.htm  Accelerator Mass Spectrometry

http://www.sjbas.org/CASBulletinApril2014.pdf

http://pubs.usgs.gov/circ/2004/1267/pdf/Tufas%20of%20Pyramid%20Lake.pdf The Tufas of Pyramid Lake, Nevada

  Let me add one more  thought that I have  on this very interesting subject that it may be helpful someone in the future for `Accurate Petroglyph Age  Dating `..   Laser Ablation  isotope-ratio mass spectrometer (IRMS) allows the precise measurement of mixtures of naturally occurring isotopes and the  measurements are made by ionization of a solid source surfaces , ( it simply vaporizes and ionizes the minute area at the surface of the sample by Laser beam  ) whereas stable isotope measurements of light elements (e.g. H, C, O)  are done . In other words  it is the ideal and preferred  method to measure the particular surface(inner most –oldest layer of carbonate C14 )  for Isotope ratio , as I had explained  in my previous comment above ; the main problem of Geochemist Larry Benson`s method  that he  had used for the age determination of Boulder Petroglyphs  created over limestone rock is Accelerator Mass Spectrometry  measurement of C14 isotope  ratio  from the  carbonate crust samples ( entire crust  old and newly created (mixed) Carbonate layer over layer on the petroglyph carved surface of different color limestone .. 

   What it means  is  the  Laser Ablation Isotope-ratio Mass Spectrometer IRMS  is done by `vaporizing`  and ionizing ONLY THE SURFACE  of the sample of Carbonate layer that had occurred shortly after the petroglyph created thousands of years ago .  In other words  in order to use this method  ; you have take `Microtome cut slices tangentially ` similar cutting techniques used  for pathology specimens of tissues  or for the specimen preparations to look under the scanning electron microscope `    the  cut slices  are parallel(adjacent) to the immediate layer of petroglyph carved rock surface – CLOSER THE SLICES TO THE ROCK SURFACE MORE ACCURATE THE  LASER ABLATION  `IRMS`  BASED DATING WILL BE- ..

  This technique if properly done can be used most Petroglyphs that has Carbonate or Organic fossilized Carbon  accumulations over the Petroglyph carved surfaces . I have not seen  in literature that ANYBODY had ever used this technique YET  for Petroglyph dating ...Just the idea .. Good luck

https://en.wikipedia.org/wiki/Isotope-ratio_mass_spectrometry

http://www.ncbi.nlm.nih.gov/pubmed/21488126 Laser Ablation IRMS

The abstract and the literature link for the Laser Ablation IRMS technique  is http://onlinelibrary.wiley.com/doi/10.1002/rcm.4985/abstract

How about Terrestrial Cosmogenic Nukleides (TCN) - Method? I heard it takes a Long time but gives good results if you compare the scratched/worked part with the natural Surface.

 Well ,  Terrestrial COSMEGENIC Nuclides  for Petroglyph dating  is a nice idea  BUT when we go to the fine details of this method  we realize that too many `Variables` and` Estimates` are involved  which ultimately end up as `unknowable ` or ` not estimable `.   :

“The two most frequently measured cosmogenic nuclides are beryllium-10 and aluminum-26. These nuclides are particularly useful to geologists because they are produced when cosmic rays strike oxygen-16 and silicon-28, respectively. The parent isotopes are the most abundant of these elements, and are common in crustal material . As oxygen-16 is also common in the atmosphere, the contribution to the beryllium-10 concentration from material deposited rather than created in situ must be taken into account.10Be and 26Al are produced when a portion of a quartz crystal (SiO2) is bombarded by a spallation product: oxygen of the quartz is transformed into 10Be and the silicon is transformed into 26Al .” ( * )

  THE PROBLEMS  WITH THIS METHOD  TO BE USED FOR PETROGLYPH  SURFACE EXPOSURE  and measuring  THE RELATIVE CONCENTRATION DIFFERENCES  OF COSMEGENIC NUCLIDES  AT THE CARVED SURFACE AND THE ORIGINAL ROCK SURFACE ` ARE :

  a- The cumulative flux of cosmic rays at a particular location can be affected by several factors, including elevation, geomagnetic latitude, the varying intensity of the Earth's magnetic field, solar winds, and atmospheric shielding due to air pressure variations. RATES  of nuclide production must be ESTIMATED order to date a rock sample ..In other words YOU HAVE TO ESTIMATE THE DATE WITH SEVERAL INDEPENDENT VARIABLES which `mathematically speaking` will definitely change wildly according to each factor ..In other words it is simply becomes  `unknown`.  

  b- The `depth of the carving` on the rock surface  has to be adequately deep , rather than superficial . Since the `penetration of cosmic rays  can be deep depending to the atomic weight density of elements(shielding effect) of the minerals that make up  that particular rock .  

( * ) https://en.wikipedia.org/wiki/Surface_exposure_dating