An analysis of mixed silicic clastic and carbonate sedimentary sequence in the Middle Jurassic strata in the eastern part of the Qiangtang basin，Tibet

Abstract：Mixed silicic clastic and carbonate sedimentary sequence is developed extensively in the east basin of Qiangtang. On the basis of previous researches， the authors studied carbonate and silicic clastic mixed rock，mixed layer system and mixed sequence by means of the analysis of regional geological materials and samples. The results show that the study area is characterized by interactive sediments of silicic clastic rock and carbonate rock at the microscopic level. And in the macro-performance of the mixed sequence which composed of silicic clastic rock，carbonate rock and mixed rock. Mixed sedimentation mainly occurred in the sedimentary system of shore, carbonate slump and tidal flat-lagoon and delta. The middle Jurassic can be divided into four sequences of SQ1-SQ4. The authors investigated the relationship between mixed sedimentation and sequences and found that, on the whole, under the circumstance of dominated silicic clastic rocks, mixed sedimentation mainly occurred at the early stage of TST and the late stage of HST, whereas under the circumstance of dominated carbonates，mixed sedimentation mainly occurred at the early stage of TST and the late stage of HST.