New findings offer clues on ancient salt production

Salt, a crucial cooking ingredient, is often a feature on the dinner table that continues to quietly influence culinary culture. For archaeologists, however, it may help draw a grand picture of civilization.

Off the coast of East China, an ongoing research project which began in 2022 on the Zhoushan Islands in Zhejiang province unveils a massive, prehistoric salt production complex that would fill many gaps in academic studies, as revealed during a Thursday media conference held by the National Cultural Heritage Administration in Beijing.

"Dating back to between 4,800 and 4,500 years ago, they compose the oldest and the largest known remains of sea-salt production in China," said Zhu Xuefei, a leading archaeologist of the project from the Zhejiang Provincial Institute of Cultural Relics and Archaeology.

She added that the 60,000-square-meter Yaojiawan site in Daishan county, Zhoushan, yields the most important findings, though only 1,430 sq m have been excavated.

Archaeologists discovered workshops featuring salt production remains, including salt stoves, piles of discarded salt-making debris, areas for stacking and firing salt, zones for piling deposits, and suspected brine processing facilities. As the deposits continued to pile up over centuries, terraces rose from the ground for human settlements.

A large number of pans related to salt boiling have also been unearthed, along with small red clay pots that were possibly used to store brine.

The Yaojiawan site is only 4 kilometers from the sea, and "wan" in its name means bay in Chinese. Zhu believed it was part of a bay in ancient times, thanks to support from various high-tech analytic approaches in the lab.

Research on environmental changes in history, based on local soil samples, showed that the last time the sea inundated this area was no more than 1,000 years ago, which offered an ideal condition for salt production.

Excavations also proved that salt production activities on the site lasted until about 2,500 years ago.

Technical analysis also helps experts put the jigsaw puzzle back together. Facing numerous broken pieces of production facilities, it seemed a challenging task to tell what they were used for.

"Salt can dissolve in water," Zhu explained. "So their distribution on the facilities is random. It's difficult to figure out the original position of the pieces if we only look for salt."

Instead, researchers used X-ray fluorescence analysis to look for calcium and other elements that were precipitated in the salt production process. The presence of calcium in various components can help to identify their nature on the production line. As a result, the team gradually began to reconstruct a picture of these salt production facilities.

Chen Xingcan, a veteran archaeologist with the Chinese Academy of Social Sciences, said, "We have many ancient Chinese documents on salt production.

"But how did these facilities work in every phase? We need more physical evidence, and the new findings offer much key information."

And tracing the origins of the findings on Zhoushan Islands to 4,800 years ago offered an even bigger horizon: it was the peak time of Liangzhu culture.

The culture, known for its jade worship, rice cultivation, and water conservancy, dates back 5,300 to 4,300 years ago and was centered around the Archaeological Ruins of Liangzhu City, located in present-day Hangzhou, Zhejiang's provincial capital. The ruins are inscribed on the UNESCO World Heritage List.

"Salt production may provide a key economic pillar and offers a fresh angle to understand Liangzhu in the future," Lin Liugen, a professor of archaeology at Zhejiang University, said. "It also inspires us to wonder whether Liangzhu culture expanded to the sea as well."

Using recent findings as a benchmark, the research team has already nurtured new knowledge on previous findings, according to Zhu.

For example, a satellite photo from 1972 once showed many artificial mounds around Yaojiawan.

"They indicate salt production remains for us, and excavations prove that," Zhu said.

Archaeologists also experienced a eureka moment when they realized that many unidentified pottery pieces in local museums were actually part of salt production facilities.

"I believe Zhoushan Islands would not be the only place to have such breakthrough findings," Chen said. "Similar potteries will be found on more islands off the coast."

Matching Chen's assumption, some other key findings on salt production were also made over the past few years in coastal areas in Jiangsu and Shandong provinces. Though their vessels varied from those on Zhoushan Islands, experts pointed to the possible existence of a north-south route for technical exchanges.

"New findings rewrite the cultural history of Zhoushan Islands," Zhu said. "We're ushered to explore more topics surrounding human migration, sea island development, and social change. They prove that the southeast coast of the country has a pivotal role in forming Chinese civilization."

Contact the writers at wangkaihao@chinadaily.com.cn