中国东北兴蒙-吉黑造山带造山作用结束的标志——来自晚三叠世磨拉石(大地构造相)的证据

中国东北兴蒙-吉黑造山带广泛分布着晚三叠世的磨拉石建造，最有代表性者，一是产于造山带的双阳盆地的大酱缸组，底部具磨拉石特征的粗陆碎，堆积厚度大于400 m，上部含煤沉积，产Drepanzamites-Glocsophtllum.二是产于华北陆块及其北部陆缘造山带结合带上的抚松白水滩盆地的小营子组，下段砾岩段为磨拉石建造，厚大于351 m；上部细陆屑沉积，见多层碳质粉砂岩，产Cycadocarpidium?.sp.，Uniohuag bogoucnsis?.三是产于华北陆块上白山市石人镇石人盆地的小河口组，下段习称红石砬子砾岩，厚达570 m；上段北山含煤段产Danacopsis-Glossophyllum.它们与下伏早（中）三叠世地层或时代更老的地质体呈角度不整合接触.充分证明：兴蒙-吉黑造山带造山作用完成于早（中）晚三叠世之间，即结束于早印支期.

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-Glossophyltum 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-beating 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.