蒙古-鄂霍茨克洋闭合时限：来自大兴安岭突泉地区下白垩统与下伏地质体之间角度不整合关系的约束
Closure time of the Mongolia-Okhotsk Ocean: constraint of angular unconformity between the Lower Cretaceous and the lower geological body in the Tuquan area of the Greater Hinggan Mountains
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摘要: 蒙古-鄂霍茨克洋的闭合时限一直是地学界争论的焦点。详细的野外调查发现, 大兴安岭突泉地区下白垩统与下伏地质体之间普遍存在角度不整合关系, 上覆地层为下白垩统白音高老组沉凝灰岩, 层理产状为332°∠15°, 下伏地层构造变形强烈, 膝折褶皱发育, 且顶部见10 cm古风化壳。结合区域资料综合对比研究, 这是一个区域性角度不整合, 是鉴别造山运动的直接标志之一。此不整合面既代表蒙古-鄂霍茨克洋在早白垩世前闭合碰撞造山, 又暗示从早白垩世开始进入东部大陆边缘向东蠕散伸展演化阶段。Abstract: The closure time of the Mongolia-Okhotsk Ocean has always been the focus of geological debate.Detailed survey shows that there is an angular unconformity between the Lower Cretaceous and the lower geological body in Tuquan area of the Greater Hinggan Mountains, The overlying stratum is the tuff of the Lower Cretaceous Baiyingaolao Formation with the stratification of 332°∠15°.The structural deformation of the underlying strata is strong, and genicular folds are developed, and 10 cm ancient weathering crust is seen at the top.Combined with the comprehensive study of regional data, the unconformity is a regional angular unconformity, which is one of the marks to identify the orogenic movement.The unconformity may not only represent the closed collision orogeny of the Mongolia-Okhotsk Ocean before the Early Cretaceous, but also suggest that the evolution stage of eastward creep and extension of the eastern continental margin began from the Early Cretaceous.
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