College of Earth Sciences, Jilin University, Changchun 130061, China

In order to understand the sedimentary environment and paleoclimate of the Meso-Neoproterozoic in Jizhou, Tianjin, the Wumishan and Hongshuizhuang formations in Jizhou are taken as examples and the geochemical characteristics are studied combining with the outcrop investigation on the basis of the geological and sedimentary background of Yanliao Aulacogen. The results show that: ① The sedimentary facies of Wumishan Formation and Hongshuizhuang Formation are carbonate platform facies, of which Wumishan Formation is mainly tidal-flat subfacies，showing the depositional rhythm of supratidal-intertidal-subtidal zones, while the Hongshuizhuang Formation comprises mainly lagoon subfacies. ②Carbonate rocks are developed in Wumishan Formation. The chemical composition of the samples is mainly CaO and MgO with similar contents. High SiO₂ content indicates that carbonate rocks were mixed with terrestrial debris during the deposition. Mudstone and shale are developed in Hongshuizhuang Formation, and the chemical composition of the sample is mainly SiO₂.③Magnesium-aluminum ratio (8~21 670) indicates that the Wumishan Formation and Hongshuizhuang Formation were deposited in a lagoon carbonate environment. The lower m value(8~12) in Hongshuizhuang Formation indicates that fresh water was injected. ④The content of Mn and Na/Al show that Wumishan Formation was generally deposited in a dry paleoclimate, with frequent transition between arid and humid climates. The climate during the deposition of Hongshuizhuang Formation was warm and humid.