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Revealing ancient rock art secrets using X-ray's vision;

Revealing ancient rock art secrets using X-ray's vision;

A mobile X-ray device has revealed a new insight into the pigments used in rock art without harming the site. Credit: Shumla Archaeological Research and Education Center

Prehistoric rock paintings are a source of interest across the world. Apart from its beauty, these strokes have a deep meaning, showing ancient rituals and important symbols. To learn more about these murals, historically researchers have turned to sampling methods that are harmful to the artwork, contradicting the archaeological conservation holdings. Today, scientists report that they have used an "X-ray vision" to get a brand new insight into layers of paint in rock art in Texas without unnecessary damage.

The researchers will present their results today at the 2019 American Chemical Society (ACS) National Spring Meeting and Exhibition.

"In this particular work, we used a technique called the X-ray (pXRF) fluorescence mobile spectroscopy, where a hand tool can be transported to a site and used there, in the van where, "says Karen Steelman, Ph.D. , who led the study. "It gives you an elementary analysis of specific material, and this is the first step in how ancient artists used different materials to make their paintings."

Steelman's research focuses on rock and cave art analysis, particularly in Lower Canyonlands Pecos in Texas. She and colleagues at the Shumla Center for Archaeological Research and Education have analyzed pigment composition in more than 10 sites in the region before, but were unable to see the bigger picture of how these pictographs were composed. . There are other methods of pigment analysis, such as plasma mass spectrometry that have been coupled inductive, asking for a sample of the rock art concerned, which leads to damage to; and site microscopes cannot detect paint layers in a complex mural.

For this particular study, Steelman visited colleagues at the Rattlesnake Canyon Site along the Rio Grande, known for its variety of illustrations. Using a 105ft wide mural as their test canvas, pXRF was used to measure 138 areas where the composition showed red, black, white and yellow pigments overlapping. In addition, measurements were taken in 90 locations of unpainted limestone, which provided an insight into the composition of the geological canvas.

Using the large amount of data collected from Rattlesnake Canyon, the team could set a pattern to the layers of pigment, as well as their elementary composition. The pXRF measurements revealed layers of black injection not previously seen under layers of red, made with manganese and iron oxide, respectively. These complex layers of pigment showed a level of sophistication seen in other Lower Pecos sites, which ethnographers have decided are a series of religious murals which revealed the complex nature of the hunter-gatherers' society occupying the region. from 2500 BCE to 500 CE.

In addition to their findings on the composition of the pictographs, Steelman, along with fellow colleagues Shumla, Victoria Roberts and Carolyn Boyd, Ph.D., found that the site appeared to include gun shooting damage. To confirm their suspicions, they again turned to pXRF to identify any trace elements that could have come from explosives. "Unfortunately, we often see suspicious bullet effects on rock art sites," Steelman said. "Most of these types of vandalism are older from the start of the 1900s, and we used the portable X-ray to determine which trace elements were present." In the impact sites, pXRF revealed the remains of lead, mercury and selenium, which were not present in the undamaged areas. A bright side to this discovery; finding damage on major archaeological sites is an opportunity to petition state and federal agencies for conservation funds to use for more extensive conservation measures.

With over 350 known rock art sites in the Lower Canyonlands Pecos only, Steelman and a team plan to continue to use pXRF to see the full picture of color tapestry and symbol to weave across the region. Flooding along the Rio Grande is a major threat to what the researchers describe as "the oldest books in North America," and they are on a mission to record and analyze as many sites as possible. keep these stories for generations and the future.

A micro-scale technique helps to preserve the legacy of rock art

More information:
Discovery of hidden layers with X-ray vision: New applications of pXRF to rock art studies, American Chemical Society American Meeting and Exhibition 2019 (ACS).

Provided by
American Chemical Society

Revealing ancient rock art secrets using X-ray's vision; (2019, April 1)
retrieved 1 April 2019

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