Abstract: The sedimentary environments of the Middle and Lower Jurassic strata are discussed on the basis of geology and geochemical signatures of the samples from the Heishi Mountains in the frontal areas of the Altun Mountains,Qinghai.It is inferred,from the horizontal stratal differences and vertical lithologic differences between the top horizons and basal horizons of the Middle and Lower Jurassic strata in the study area,that the Middle and Lower Jurassic strata on the top may be assigned to the "klippes".These Middle and Lower Jurassic strata laid down in the reducing environments are favourable for the preservation of organic matter and generation of the source rocks,indicating the potential of oil and gas exploration.