Rise and Decline of Ancient Salt Industry Revealed by the Concentrations of Naand Cain Sediments at Zhongba Site
重庆中坝遗址地层Na- Ca 元素含量 揭示的制盐业兴衰史

On the basis of archeological period division and AMS14C dating to the sedimentary layers at Zhongba and Yuxi sited, and according to the analysis results of Na, Ca and Mg in 201 sedimentary samples from Zhongba site and that of Ca and Na in 47 sedimentary samples from Yuxi site by using an inductively coupled plasma-mass spectrometry (ICP), we found that there were 35 correlation periods when the contents of Ca and Na were reversely correlated, that is to say, whenever the content of Ca was the highest, the content of Na was the lowest, and vice versa. Among them, there were 21 correlation periods when the content of Ca was the highest, and Na was the lowest, indicating that there were about 21 prosperous periods of ancient salt production at Zhongba site since 3000 BC. Other 14 correlation periods with the peak values of Na while the low values of Ca indicate that there were about 14 declined periods of salt production at Zhongba site since 3000 BC. The conclusion obtained from the reverse relationship between Ca and Na contents in this paper is consistent with that "the salt production at Zhongba site started in the new stone age, developed in the Xia and Shang dynasties, reached at the heyday in periods from the Western Zhou to the Han Dynasties, maintained stable to develop in the Tang and the Song dynasties, and gradually declined after the Song Dynasty because the sea salt was conveyed into Sichuan region, however, still had production in the 1970s and 1980s educed from archeological exploration.