PETROGLYPHS – DATING THE OTHER 95% OF ROCK ART

Society for American Archaeology, Sacramento, California, March 30—April 3, 2011
By Bryan C. Gordon, Canadian Museum of Civilization

I changed my title and contents to reflect research done since my abstract. I want to show you how you can date your rock art using simple testing. My pictograph dating is seen on my website. You can also Google Gordon Carleton Dating. I will focus here on dating petroglyphs.

My pictograph dating paper at the SAA Atlanta conference was based on fallen dried red ochre droplets and dust. These were on the surfaces of 5 mm scraped levels in a 20 x 25 cm soil test under the art (Slide 1). They were separated from soil grains using the ‘similar’ and ‘inverse’ functions in art software. Pigment particles also appear on wet glue-coated paper applied to each scraped level (Slide 2). Glue sheets remove about a mm of soil, as in these Stein Valley double tests in British Columbia. The remaining 4 mm of soil is filtered through a kitchen sieve. Even a cup of seemingly sterile Mexican desert sand gave a mg or more of carbon-datable material. Other soils may contain enough carbon for a cheaper regular radiocarbon estimate.

At the Atlanta conference I gave my results on Baja California’s Montevideo pictograph. Despite finding fallen pictograph chips, a critic asked proof of particles coming from the art. If natural, they should be in most soil levels, but were not. I adopted glue paper to capture them. (Slide 3) In Stein Valley we linked ochre particles to the art using Scattered Electron Microscopy.

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Slide 1
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Slide 2
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Slide 3
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