The trace elements of sedimentary rocks have a high sensitivity on hydrological changes of sedimentary en-vironment, so the trace elements can be used as an effective method on the study of paleoclimate and paleoenviron-ment during deposition period. The Zhifang Formation in Ordos Basin is a new series of strata of Triassic with oil&gas seeps, the ancient climate and ancient water environment have great significance in restoring the ancient sedimentary framework and geography of that period and hydrocarbon accumulation. In this paper, the trace element of the profile and 21 shale and siltstone core sample of the middle Triassic Zhifang Formation in Ordos Basin have been determined by means of ICP-MS, and trace elements of strontium ( Sr ) , ba ( Ba) , thorium ( Th ) , uranium ( U ) , vanadium ( V ) , nickel ( Ni ) , cobalt ( Co ) were selected as the discriminant mark, and combining sedimentology and sporopollen analysis, the sedimentary environment and ancient climate characteristics of Ordos Basin were discussed. The results show that by Li, Sr, Ni, Ga content and the ratio of Sr/Ba indicating the sedimentary environment was con-tinental fresh -brackish water. The ratio of U/Th is from 0.09 to 0.38,δU is from 0.43 to 1.07, the ratio of V/( V+Ni) is from 0.69 to 0.89, the ratio of V/Cr is from 0.87 to 5.57, the ratio of Ni/Co is from 1.21 to 2.93, which indicate the oxidation-weak reduction environment. Combining sedimentology mark and quantitative calculation of Co elements, the average water depth of Zhifang Formation is less than 30 m, and the large catchment lake has not yet formed. The ratio of Sr/Cu is from 0.85 to 16.7, most Sr/Cu ratio is less than 10, and combining with the sporopollen analysis, which show that the dry climate of Heshanggou Formation was translated into warm climate of Zhifang Formation.%沉积岩中的微量元素对沉积环境的水介质变化有着较高的敏感度,是研究沉积物沉积时的古气候、古环境的有效手段.鄂尔多斯盆地纸坊组是三叠系具有油气显示的新层系,其古气候及古水体环境对于恢复该时期盆地沉积格局、重建古地理及成藏研究具有重要意义.采用ICP-MS对鄂尔多斯盆地纸坊组剖面及岩芯21件泥岩及粉砂岩样品进行了微量元素测试,选择对沉积环境介质较为敏感的锶(Sr)、钡(Ba)、钍(Th)、铀(U)、钒(V)、镍(Ni)、钴(Co)等元素作为判别指标,并结合沉积学标志及孢粉分析,对鄂尔多斯盆地纸坊组沉积环境及古气候特征进行研究.结果表明:通过Li、Sr、Ni、Ga含量及Sr/Ba值判别研究区为淡水—微咸水沉积环境;U/Th值分布在0.09~0.38,δU值分布在0.43~1.07,V/(V+Ni)值分布在0.69~0.89,V/Cr值分布在0.87~5.57、Ni/Co值分布在1.21~2.93,指示水体分层不强的氧化—弱还原过渡环境;纸坊组水体深度平均深度小于30 m,大型"汇水"湖泊尚未形成;Sr/Cu比值在0.85~16.7之间,大部分小于10,仅个别值大于10,表明纸坊组古气候已由和尚沟组干热气候趋于温暖气候.
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