ENDING OF THE MOUNTAIN-BUILDING MOVEMENT OF XING'AN-MONGOLIAN-JI-HEI OROGENIC BELT IN NORTHEAST CHINA: Evidence from Late Triassic molasse(geotectoinc phase)

The Late Triassic molasse formations are widely distributed in Xing'an-Mongolian-Ji-Hei orogenic belt in Northeast China. Three of them are the most representative:1) The Dajianggang formation in Shuangyan basin in the orogenic belt, with coarse terrestrial fragments more than 400 m thick in the bottom, and coal-bearing sediment containing Drepanzamites-Glossophyllum in the top. 2) The Xiaoyingzi formation in Baishuitan basin on the epicontinental orogenic belt of North China Landmass, with conglomerate over 351 m thick in lower member, and fine terrestrial fragment sediment in upper, with interbeds of carbonaceous siltstone and fossils of Cycadocarpidium? sp. Uniohuag bogouensis? 3) The Xiaohekou formation in Shiren basin on North China Landmass, with the Hongshilazi conglomerate up to 570 m thick in the lower member, and the upper coal-bearing Beishan member, containing Danaeopsis-Glossophyllum. These molasses formations contact the underlying Early/Middle Triassic or older strata with angular unconformity. Those thoroughly prove that the mountain-building movement of Xinmeng-Jihei orogenic belt was completed between Early/Middle and Late Triassic, which means it ended in Early Indosinian period.