黔西北奥陶系下统砾岩的发现及其构造意义

王波; 邓新; 唐婷婷; 朱华利; 谯常; 杨坤光

王波,邓新,唐婷婷,朱华利,谯常,杨坤光.黔西北奥陶系下统砾岩的发现及其构造意义[J].贵州地质,2017,34(1):38-44

黔西北奥陶系下统砾岩的发现及其构造意义

Discovery and Its Tectonic Significance of the Conglomerate from the Lower Ordovician in the Northwestern Guizhou

DOI：

中文关键词: 砾岩地层对比奥陶系构造意义黔西北

英文关键词:Conglomerate Stratigraphic correlation Ordovician Tectonic significance Northwestern Guizhou

基金项目:中国地质调查局地质调查工作项目《贵州乌蒙山区1∶5万天鹅池等四幅区域地质调查》（编号：121201010000150002-09）；《贵州1∶5万毕节等六幅区域矿产地质调查》（编号：1212011220407）；2010年度贵州省地矿局局管重大科研项目之《贵州区域构造特征、构造演化与矿产空间分布关系研究》项目资助。

作者	单位
王波	贵州省地质调查院
邓新	中国地质调查局武汉地质调查中心，湖北武汉430025
唐婷婷	贵州省地质调查院
朱华利	贵州省地质调查院
谯常	贵州省地质调查院
杨坤光	中国地质大学（武汉）地球科学学院，湖北武汉430074

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中文摘要:

黔西北位于扬子板块的西南缘，经历了新元古代板块拼接碰撞造山运动及早古生代加里东期陆内造山运动的复杂演化过程，尤其是加里东期的三幕（郁南、都匀、广西）构造运动造成早古生代地层不同程度的缺失。本研究在黔西北毕节地区首次发现早奥陶世湄潭组与桐梓组之间存在一套以硅质砾石为特征的砾岩层。通过地质剖面测制、镜下岩石学分析、地层对比及古生物化石鉴定等手段，对该砾岩层区域产出特征、岩石学性质及横向地层对比等进行综合研究，笔者认为包括研究区在内的黔中地区，在早奥陶世曾发生短暂的水上隆升，以致该阶段岩石地层单元出现平行不整合接触界面，以湄潭组粘土岩假整合于娄山关组白云岩之上标志着本次隆升结束。综合构造变形与沉积环境的研究认为，郁南运动阶段，贵州大部表现为水下隆起和海盆变浅，大面积沉积早奥陶世早期碳酸盐岩，但毕节地区出现短暂的抬升为古陆剥蚀区；都匀运动自南向北挤压，形成东西向黔中隆起，以遵义—毕节—赫章为界，黔西北为沉积整合区，黔中为假整合区。

英文摘要:

Located in southwest margin of Yangtze Block，the northeastern part of Guizhou exprienced a complicated evolution process from the Neoproterozoic plates convergence and collision orogenesis to the Early Paleozoic Caledonian intracontinental orogenyThis process，especially the three stages of Caledonian tectonic movements（Yunan Orogeny，Douyun Orogeny and Guangxi Orogeny），results in the lost stratum of different degreesIn our study area，at the Bijie District，we find a conglomerate layer characterized by siliceous gravels between the Lower Ordovician Meitan Formation and Tongzi Formation for the first time everBy measuring and mapping geological profile，microscopic analysis of petrology，stratigraphic correlation，identification of ancient fossils and so forth，we have led a comprehensive research in the occurrence，petrologic features，horizontal strata correlation and other aspects of the conglomerate layerWe reckon that the middle part of Guizhou，including our study area，experienced brief uplifts above water in the Early Ordovician，leading to the forming of a parallel unconformable contact between the stratagraphical units within this stageAnd the parallel unconformity of the clay rock of Meitan Formation overlapping on the dolomite of Loushanguan Formation marked the end of this upliftTaking the tectonic deformation and sedimentary environment into consideration, we conclude that a brif uplift turned the Bijie District into an ancient denudation area while most parts in Guizhou underwent uplifts under water and shallowing of sea basins with the result of Early Ordovician carbonates sedimentation in large area during the stage of Yunan Orogeny；the middle part of Guizhou uplifted in the Douyun movement with its compression from south to north；the northwest Guizhou is an area of successive sedimentation with stratigraphic conformity，while the middle Guizhou is sedimentation hiatus with stratigraphic disconformity.

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