TECTONIC SIGNIFICANCE OF SANDSTONES AND COUPLING RELATION OF BASIN AND MOUNTAIN IN THE LATETRIASSIC-JURASSIC IN THE MIDDLE AND UPPER YANGTZE REGION

Based on the sandstone clastic model built by Dickinson et al,the characteristics of detrital composition of the Late Triassic-Jurassic sandstones in the Middle and Upper Yangtze region are studied to determine the types of source areas.It is presented that the main provenances of the Late Triassic-Jurassic basin comes from the East Qinling and Dabie orogenic belt,Longmenshan mountain and Jiangnan obduction zone.The main types of provenances attribute to the properties of recycled orogenic belt.The variational sequences of detrital compositions are the sedimentary responses to the three times of obduction of orogenic belt in the surrounding margin of basin.The analysis on the tectonic significance of detrital composition of the Late Triassic-Jurassic sandstones shows that the Late Triassic-Jurassic basin in the southern margin of the East Qinling and Dabie orogenic belt is a foreland basin located in the foreland of a collision orogen and thrusting nappe belt.The coupling relations of basin and mountain and Mesozoic tectonic evolution in the East Qinling and Dabie orogenic belt were also discussed in this paper.