On a Chinese River, Archeologists Discover Salt’s Ancient History

The oldest confirmed salt production facility in China has been identified in an area of the Three Gorges scheduled to be flooded by a new hydroelectric dam, a team of Chinese and American archeologists announced this week in the Proceedings of the National Academy of Sciences.

The 4,000-year-old facility at Zhongba on the Ganjing River in central China was a major source of wealth and power for the emerging civilizations of the second millennium BC. Salt production has continued in the area ever since.

The site is located on a mound in the middle of the Ganjing, just three miles from the Yangtze River and about 120 miles downriver from the city of Chongqing.

The site is crucial for understanding the genesis of civilization in the region because of the importance of salt. Not only is salt a necessary dietary supplement and an agent for preserving meat, but it also was a valuable trade item and, therefore, a source of cultural influence.

No confirmed salt-making facilities had previously been identified in the country.

Rowan Flad of Harvard University and a team from several Chinese institutions found large quantities of three different types of pottery that were typically used for boiling water to crystallize salt. They also found oval pits with a thick clay lining that were used to concentrate brine.

High levels of magnesium and calcium on the earth surfaces at the site and in the pits correlated with the presence of those metals in the brine, indicating that salt production was occurring.

Residues in the bottoms of the pottery contain not only those elements, but also calcium oxide compounds that are still used by salt-makers in the region to remove impurities from the brine.

Flad speculated that the techniques developed by the team to study the residues in soil and pottery could also be used elsewhere to confirm the existence of salt-producing facilities.