West Texas prehistoric paintings get laser study


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A complex colorful mural painted on canyon walls some 4,000 years ago in West Texas is getting modern laser treatment as researchers try to unlock its mysteries and protect it from the unintended consequences of a nearby reservoir. 

Archaeologist Carolyn Boyd inspects prehistoric paintings at Panther Cave in Seminole Canyon State Park and Historic Site in Comstock, Texas. Researchers are using 3D scanning equipment to help with study of the paintings and develop plans to better preserve them [Credit: Michael Graczyk/AP]

Panther Cave, among the best known of several hundred prehistoric pictograph sites that dot the rugged canyons along the US-Mexico border, is being scanned with lasers to produce a high-resolution 3-D image in efforts to gauge the mural’s deterioration and detect images long ago erased by Mother Nature. They hope the project will help them preserve and decipher one of the oldest stories in North America. 

“They are ancient texts, not just drawing on walls,” says Carolyn Boyd, head of the Shumla School, an archeological research center working with state and federal agencies on the project. “We have knowledge now that these paintings are far more than graffiti. And with knowledge comes responsibility — a responsibility to take care of it.” 

Carbon dating shows the Panther Cave paintings — a combined 150 feet wide and 13 feet high — were made by prehistoric Native Americans at the same time the Egyptians were constructing the pyramids. Some images have human characteristics, some are unknown and some are animal figures, including the cave’s unmistakable signature 12-foot-long leaping red panther. The animal guards the hollowed out cavern overlooking the Rio Grande about 50 miles west of Del Rio. 

The two-week scanning process, extending into early June, will eventually give researchers a precise base line to track what appears to be accelerated deterioration due to increased moisture from the Amistad Reservoir and insects building nests or burrowing into the porous limestone walls. 

A camera about the size of a microwave oven passes over a 6- to 10-inch square per scan, collecting images accurate to 1mm. Color photographs are then overlaid on the images to give researchers a clear picture of how the site has changed over the centuries. Other images taken with color-sensitive photo equipment show parts of the paintings no longer visible. 

“It’s a powerful tool to see how the site has changed,” said Christopher Goodmaster, an archaeologist and laser scanning specialist. 

Goodmaster connects his equipment to a car battery for power and collects the individual images on a laptop computer. Like building a puzzle, he said he “mosaics it together to make sure we’re getting it all.” 

The project is expected to help researchers determine how increased populations of wasps and environmental effects are changing the paintings over the years. Photos from earlier decades don’t show the wasp infiltration, and some researchers speculate that the creation of the nearby Amistad Reservoir has made it easier for the insects to get their mud and make their nests here. The gigantic reservoir was created in 1969 when damming of the Rio Grande began flooding the steep canyons. 

“If you have one under your house, you take a pressure washer and whack it off,” said Jack Johnson, a park archaeologist for the Amistad National Recreation Area. “You can’t do that here.” 

One wasp, known as a mud dauber, builds pipe-like nests of mud that attach to the surface of the painted walls and harden like concrete. If and when the nests fall, they can take the paint with it. The second, called a blue dauber, infiltrates the natural holes in the limestone — smaller than the circumference of a drinking straw — for its nest and then seals the hole with its plaster-like mud. When its offspring emerges, it breaks through the plaster that also takes with it the limestone surface — and the paint — around the edge of the hole. 

“I just wish they’d go somewhere else,” Johnson said. 

Before Amistad was built, the floor of Seminole Canyon was about 300 feet below Panther Cave. Now the water is close. Although visitors only can reach the area by boat, they need to only climb a couple steel staircases attached to a dock to see it. The cave itself is corralled by a tall chain link fence topped by curled razor wire to deter vandals or souvenir seekers. 

The increased moisture from the reservoir also contributes to spalling, the weakening of the cave surface that causes it to flake off. 

Boyd believes the prehistoric paint was made of mineral pigments that gave it color and deer or bison fat held it together. It also may contain juice from yucca plants. The paint was applied with brushes of animal hair, feathers or fingers. Some of the images are extremely precise, indicating sophisticated measuring devices were employed. 

Given the height of the cave and size of some of the paintings, a form of scaffolding must have been used to reach the upper levels, like the area of “the big fat guy,” as Boyd laughingly identified one human-like image to some of her archaeology students involved in the project. 

“This one’s huge,” she exclaimed. “Look at him!” 

For data collection purposes, the figure depicted is now known as Anthropomorph 0083-A064. He’s 12 feet tall and 16 feet wide from the atlatl — a spear thrower — in his right hand to a power bundle of spears and a kind of boomerang in his left hand. He has adornments on his elbow and wrist and what looks like feathers at his hip. 

He joins at least four panthers in the cave, painted with shades of red, brown, yellow and black, and multiple “enigmatics” — images that still baffle archaeologists. There’s a large upside-down bat-like creature and several miniature versions, and some black rectangles and recurring symmetrical figures that appear to be a theme. 

“These folks didn’t have a written alphabet, so all of their knowledge, their history … is here on the wall,” Johnson said. 

“My job is to preserve this and keep it as it is so we can come back to it, back in another 1,000 years.” 

Author: Michael Graczyk | Source: Associated Press [May 29, 2011]



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