摘要:
湘西北地区是指位于湖南省内的桃源、沅陵、怀化一线以北及以西的区域.根据2010年以来在区内开展1∶5万区域地质调查项目所取得的剖面资料及填图资料,应用优势相成图法编制了早奥陶世特马豆克期、弗洛早期的岩相古地理图.基于岩相古地理研究表明:沿张家界—古丈—吉首—凤凰一线有古隆起的存在,大致以古隆起为界,两侧沉积分异明显;西北侧属镶边碳酸盐岩台地,沉积地层为桐梓组和红花园组,主要发育局限台地、开阔台地、台地边缘浅滩、台地边缘生物礁、台地斜坡和浅海陆棚6种沉积相和若干亚相、微相;东南侧属浅海陆棚,沉积地层为白水溪组盘家咀组、桥亭子组,主要有混积陆棚和碎屑陆棚.沉积特征的分析和系列岩相古地理图件的编制,提高了区内下奥陶统的研究程度,同时对金属地质找矿具有一定的指导意义.%Xiangxibei area refers to the northwestern Hunan Province mainly,Taoyuan,Yuanling,Huaihua cities.Lithofacies have been investigated,on the basis of the key Lower Ordovician sections collected during the field mapping projects.The lithofacies palaeogeography maps of the Tremadocian and Floian ages are presented here.The lithofacies palaeogeographic analyses suggest that there was a palaeouplift in areas of Zhangjiajie-Guzhang-Jishou,which shows the significant difference in lithofacies between both sides of the palaeo-uplift.The Tongzi and Honghuayuan Formations were formed on carbonate platform facies in the northwestern of palaeo-uplift,including six types of subfacies,including restricted-platform,open-platform,platform edge,marginal reef of platform,platform slope and shollow sea shelf.The Baishuixi/Panjiazui and Qiaotingzi sormations were formed on the shelf in the southeastern of palaeo-uplift,including two types of facies (i.e.,mixed shelf and clastic shelf).Results from this work improve the understanding of the Early Ordovician,and provide important information for evaluation of geological prospecting in the area.