That, in turn, may have spurred the ancient Chinese culture to move closer to the new river flow, study co-author Niannian Fan, a river sciences researcher at Tsinghua University in Chengdu, China, said Dec. 18 at the 47th annual meeting of the American Geophysical Union in San Francisco.
In 1929, a peasant in Sichuan province uncovered jade and stone artifacts while repairing a sewage ditch located about 24 miles (40 kilometers) from Chengdu. But their significance wasn't understood until 1986, when archaeologists unearthed two pits of Bronze Age treasures, such as jades, about 100 elephant tusks and stunning 8-feet-high (2.4 meters) bronze sculptures that suggest an impressive technical ability that was present nowhere else in the world at the time, said Peter Keller, a geologist and president of the Bowers Museum in Santa Ana, California, which is currently hosting an exhibit of some of these treasures.
The treasures, which had been broken and buried as if they were sacrificed, came from a lost civilization, now known as the Sanxingdui, a walled city on the banks of the Minjiang River.
"It's a big mystery," said Keller, who was not involved in the current study.
Archaeologists now believe that the culture willfully dismantled itself sometime between 3,000 and 2,800 years ago, Fan said.
"The current explanations for why it disappeared are war and flood, but both are not very convincing," Fan told Live Science.
But about 14 years ago, archaeologists found the remains of another ancient city called Jinsha near Chengdu. The Jinsha site, though it contained none of the impressive bronzes of Sanxingdui, did have a gold crown with a similar engraved motif of fish, arrows and birds as a golden staff found at Sanxingdui, Keller said. That has led some scholars to believe that the people from Sanxingdui may have relocated to Jinsha.
But why has remained a mystery.
Geological and historical clues
Fan and his colleagues wondered whether an earthquake may have caused landslides that dammed the river high up in the mountains and rerouted it to Jinsha. That catastrophe may have reduced Sanxingdui's water supply, spurring its inhabitants to move. [History's 10 Most Overlooked Mysteries]
The valley where Sanxingdui sits has a large floodplain, with 4.3 miles (7 kilometers) of high terraced walls that were unlikely to have been cut by the small river that now flows through it, Fan said.
And some historical records support their hypothesis. In 1099 B.C., ancient writers recorded an earthquake in the capital of the Zhou dynasty, in Shaanxi province, Fan said. Though that spot is roughly 250 miles (400 kilometers) from the historic site of Sanxingdui, the latter culture didn't have writing at the time, so it's possible the earthquake epicenter was actually close to Sanxingdui — but it just wasn't recorded there, Fan said. Geological evidence also suggests that an earthquake occurred in the general region between 3,330 and 2,200 years ago, he added.
Around the same time, geological sediments suggest massive flooding occurred, and the later-Han dynasty document "The Chronicles of the Kings of Shu" records ancient floods pouring from a mountain in a spot that suggests the flow being rerouted, Fan said. (Around 800 years later, Jinsha residents built a wall to prevent flooding.)
A river rerouted?
Together, the findings hint that a major earthquake triggered a landslide that dammed the river, rerouting its flow and reducing water flow to Sanxingdui, Fan said.
But if so, where did the river get rerouted? The team found clues high up in the mountains in the deep and wide Yanmen Ravine, at about 12,460 feet (3,800 meters) above sea level.
The modern-day river cuts through the ravine, which was carved by glaciers about 12,000 years ago. Yet the telltale signs of that glacial erosion — bowl-shaped basins known as cirques — are mysteriously absent for a long stretch of the ravine. The team hypothesizes that an earthquake spurred an avalanche that then wiped out some of the cirques about 3,000 years ago.
At this point, the theory is still very speculative, and additional geological data is needed to buttress it, Fan said.
And while the geological story is possible, Keller said, it doesn't answer the basic question: "What would motivate people to destroy their entire culture and bury it in two pits? And why didn't the culture reemerge at Jinsha?"
source: livescience.com by Tia Ghose