“Open-Close” Evolution and Triassic Tethyan-Type Sedimentation in Qinling Orogenic Belt

The Triassic stratum in Qinling is boundary by regional fault in north and south, with east-westzonal distribution, which is connected with Paleotethys flysch in Bayakala area to the west, with wedgeshape. It is characteristics by great thickness and unique construction, in cluding deep water gravity flow, collapse accumulation, and slippery mixed turbidites. Moreover, the Triassic stratum has plastic flow structure and longitudinal fold, which is stronger than Pre-Triassic stratum in neighborhood area, indicating aulacogen sedimentary and evolution features. The aulacogen was opened in Middle Triassic and closed in late stage of Middle Triassic toearly stage of Late Triassic. The Triassic stratum in Qinling isobvious different from the Yangtze-type platform in China, which recorded a complete"open-close"tectonic event with relatively independent setting and specific strain domain.