SEDIMENTARY GEOLOGY AND DYNAMIC SEDIMENT-OLOGY OF THE DEVONIAN STRATA IN THE WEST QINLING OROGENIC BELT: SEDIMENTARY CHARACT-ERISTICS AND FRAMEWORK OF THE DEVONIAN RIFT TROUGH AND MOTIANLING TERRANE IN THE SOUTHERN BELT OF THE WEST QINLING OROGENIC BELT

The southern Qinling rift trough is installed between the Qinling mieroplate and Mo-tianling terrane. The stress in this article is put on the stratigraphy,sedimentology,volcan-ism and palaeobiogeography of the Devonian strata in the rift trough and Motianling ter-rane,as well as their depositional systems and basin framework. The Devonian Sanhekou Group in the rift trough consists of metamudstone,silty mudstone and thin-to thick-bed-ded lime mudstone in deep-water basin and shelf environments interstratified with tholeiite and alkali basalt. The chemical analysis and REE distribution patterns of tholeiite and al-kali basalt indicate the existance of the rift trough during Devonian time. The Devonian strata in the Motianling terrane are made up of terrigenous nearshore and shelf deposition-al system,and carbonate ramp and shelf depositional systems. The terrane is interpreted as part of the northern continental margin of the Yangtze plate.