Ever since British astronomer Gerald Hawkins theorized in 1983 that Stonehenge was erected for astronomical observations, people have sought similar interpretations in ancient American Indian rock art.
Two men now say the petroglyphs in Parowan Gap were an Indian observatory to rival Stonehenge.Some experts are skeptical.
Garth Norman and Nal Morris say the petroglyphs show the Fremont Indians used the 600-foot-high cliffs in the narrow canyon to track the sun and moon.
One petroglyph panel shows a V-shape form they interpret as a calendar marking the start of summer and winter, they said.
"This was a massive observatory," said Norman, president of Archaeological Research Consultants in American Fork.
"It outstrips Stonehenge hands down," he told The Salt Lake Tribune.
Norman and Morris, a physicist, aren't the only ones who believe Parowan Gap was an ancient observatory.
Steve Manning, an amateur rock-art researcher, has done his own studies in the area and also has concluded that people were tracking the sun.
But he contends Norman and Morris "have gone far beyond what I consider to be reasonable" in their detailed interpretation of the rock art.
Manning, who is in charge of hazardous-waste disposal at the University of Utah, said Parowan Gap was a special site to the Indians because the axis of the canyon lines up naturally with sunrise on the winter solstice and sunset on the summer solstice.
Some archaeologists are skeptical of such claims. Similar "discoveries" have been announced by many other people, and few have withstood rigorous scientific review. Neither Norman and Morris nor Manning have published their conclusions in a peer-reviewed archaeological journal.
Parowan Gap cuts through the Red Hills, a low range of mountains that forms the western border of the Parowan Valley. Most of the petroglyphs are near the northern end of the gap, about 13 miles west of Parowan.
Based on the style and design of the images pecked into the rock, most archaeologists believe this gallery represents the accumulation of at least 1,000 years of art, stretching from the ancient Fremonts to the ancestors of present-day Southern Paiute Indians. Some of the art could be much older.
Images of lizards, snakes, mountain sheep, bear claws and humans decorate the cliffs, along with hundreds of abstract, stylized forms that have baffled modern observers.
Norman and Morris interpret an abstract rock-art panel known as the "zipper" as both a map and calendar. There are 180 cross-hatches on the V-shape form, which could correspond to the half-year between the summer and winter solstice. And the V-shape could represent the sun's movement along the horizon between the solstices.
They say another panel with 19 bars was a lunar calendar. Morris said if an observer stands next to the panel and views the moon through a nearby crack, it aligns with the moon's position once every 19 years.
What could be stone mounds have been discovered on the west and east sides of the gap where the Indians might have stood to watch the rising and setting sun. The sun in the gap aligns with these mounds on several days in the solar calendar.
Manning's more conservative claims for this site are based on two rock-art symbols he has found in areas throughout the West. They are concentric circles he interprets as the sun, and a series of triangles he says indicate time.
Using these symbols, he has been able to predict when the rising or setting sun will line up with a distant peak, butte or some other obvious topographic feature at 15 sites stretching from northern Utah to New Mexico.
"They marked the spot where they watched these events," says Manning. "I haven't found any that don't work. That's what makes this neat."
Williamson has found at least two buildings and a rock-art panel at Hovenweep National Monument that he believes were used to track the seasons.
Von Del Chamberlain, director of Hansen Planetarium, said Williamson's study is the "most convincing" evidence he's seen of archaeo-astronomy sites in the Southwest, but he remains cautious about most other claims.