Abstract:

Dark red mudstone interbedded gypsum of late Cretaceous was developed in the Luotang depression in Xinjiang Basin,
Jiangxi. Gypsum trace element geochemical characteristics provide ways to decipher the depositional environment, together with well log data. This study shows that: (1) Gypsum was mainly developed in the second, third, and fourth section in Zhoutian Formation, which consists of gypsum-bearing calcium mudstone and muddy gypsum rock and a small amount of (hard) gypsum rocks; (2) Trace normalized patterns show that gypsum and wall rocks were terrigenous rather than deep brine sources; (3) Gypsum was developed in shallow water and deep water in early and late stage, respectively. It was probably located at the edge of basin in early stage, intercalated with purple calcareous mudstone tuberculosis gypsolith. It was mainly distributed in the central basin with gypsum rock and dark mudstonedeposition in the late stage，forming rhythmic salt layers. From the edge to the center of the basin, it was deposited as typical evaporite sequence from carbonate rocks togypsolith.

Key words: Xinjiang Basin, Luotang depression, gypsum rock, trace element