Keywords: 
• Songliao Cretaceous /
• evaporite /
• marine water input /
• palaeoenvironment condition

Abstract: The studied well of S113 is situated on the Sanzhao downwarp of the Songliao Basin. About 500m core sequences containing evaporite of Quantou formation (Albian) in the well were systematicly researched and described in their sedimentary sequences,structural and fabric features, mineral associations, as well as elemental geochemical and isotopic characteristics.According to the above studies,the authors concluded as following:1. The evaporites which are mainly anhydrite,barite as well as celestine and gypsum have two kinds of mineral associations and the cementation order of the minerals ought to be ba rite →calcite→celestine and calcite →gypsum (anhydrite) respectively, which agree with their solubilities.2. The palaeoenvironmental conditions were PH=9, Eh=0. 1, SO₄^2- = 3084mg/L and CO₃^2-= 102mg/L,which were the contents in between playa-lake and marine water.3. There were two sources for forming evaporites-episodical marine water input and continental sources which were mainly composed of meteoric water and oxidation of pyrite from C-P shales and Yanshanian igneous rocks.The ratio of volume of marine input to volume of continental input lay between 0: 12. 6: 1. 4. The marine water input became significant approximatly during the period of 102Ma,106Ma and 107Ma, which agree with the Mid-late Albian eustasy.5. Formed in the arid playa mud flat or salina, the evaporites deposited near water table. And the eolian effect could occasionally become significant.