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| 扬子北缘元古宇马槽园群时代归属新证据 ——对地层对比和古地理格局的启示 | |
| 引用本文： | 邓 奇,王 剑,汪正江,邱艳生,杨青雄,江新胜,杜秋定.扬子北缘元古宇马槽园群时代归属新证据 ——对地层对比和古地理格局的启示[J].地质通报,2013,32(4):631-638. |
| 作者姓名： | 邓 奇 王 剑 汪正江 邱艳生 杨青雄 江新胜 杜秋定 |
| 作者单位： | 1. 中国地质科学院研究生院,北京100037;中国地质调查局成都地质调查中心,四川成都610081 2. 中国地质调查局成都地质调查中心,四川成都,610081 3. 湖北省地质调查院,湖北武汉,430034 |
| 基金项目： | 国家自然科学基金重点项目《华南新元古代"楔状地层"沉积序列及其大地构造属性研究》，国家自然科学基金面上项目《黔东新元古代中期沉积盆地演化与地层划分对比研究》，中国地质调查局计划项目《扬子地块东南缘罗迪尼亚超大陆解体及沉积-成矿响应综合研究》，《扬子北缘马槽园群沉积充填序列及其沉积大地构造研究》 |
| 摘 要： | 马槽园群是华南前寒武纪地层中的重要单元,其沉积特征及时代归属对建立和完善扬子北缘地层格架、认识和恢复当时的古地理格局有重要意义.通常认为,扬子北缘马槽园群(下部八里垭组,上部火烧尖组)是一套角度不整合于中元古界神农架群之上的新元古代磨拉石建造.取自该群下部八里垭组上部的同沉积凝灰岩样品的高精度离子探针(SHRIMP)锆石U-Pb年龄为(1165±14)Ma.该年龄数据表明,马槽园群沉积地层的形成时代应为中元古代,而不是新元古代.野外调查与沉积相分析表明,马槽园群沉积地层中滑塌包卷、正粒序等重力流沉积构造发育,主体为一套斜坡相碳酸盐岩重力流沉积,而非磨拉石建造.结合前人研究结果认为,马槽园群无论是在沉积特征还是时代归属上都不能与华南新元古代裂谷系地层进行对比,而应该属于裂谷系之下的基底地层. |
| 关 键 词： | 马槽园群 凝灰岩 锆石U-Pb年龄 中元古代 扬子北缘 |
New evidence for the age of the Macaoyuan Group on the northern margin of the Yangtze block, South China—implications for stratigraphic correlation and palaeogeographic framework |
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| DENG Qi,WANG Jian,WANG Zheng-jiang,QIU Yan-sheng,YANG Qing-xiong,JIANG Xin-sheng,DU Qiu-ding.New evidence for the age of the Macaoyuan Group on the northern margin of the Yangtze block, South China—implications for stratigraphic correlation and palaeogeographic framework[J].Geologcal Bulletin OF China,2013,32(4):631-638. | |
| Authors: | DENG Qi WANG Jian WANG Zheng-jiang QIU Yan-sheng YANG Qing-xiong JIANG Xin-sheng DU Qiu-ding |
| Institution: | 1. Graduate School of Chinese Academy of Geological Sciences, Beijing 100037, China; 2. Chengdu Center, China Geological Survey, Chengdu 610081, Sichuan, China; 3. Hubei Institute of Geological Survey, Wuhan 430034, Hubei, China |
| Abstract: | The Macaoyuan Group is an important stratigraphic unit of the Precambrian strata in South China, so its sedimentary characteristics and ages are of great importance for the stratigraphic division and the correlation and reconstruction of the sedimentary facies and paleogeographic framework of the northern margin of the Yangtze block. It is generally accepted that the Maocaoyuan Group comprising the lower Baliya Formation and the upper Huoshaojian Formation on the northern margin of the Yangtze block consists of a succession of the Neoproterozoic molasse formation unconformably overlying the Mesoproterozoic Shennongjia Group. The SHRIMP U-Pb zircon age of the synsedimentary tuff from the upper part of the Baliya Formation is dated at 1165Ma±14Ma. This dating result shows that the Macaoyuan Group should be traced back to the Mesoproterozoic rather than previously-considered Neoproterozoic strata. Field investigation and sedimentary facies analysis demonstrate that there are slump-convolute structures and normal graded bedding formed by the gravity flow in the Maocaoyuan Group, in which the strata are mainly made up of a succession of slope carbonate gravity flow deposits, instead of molasse formation. In combination with previous research results, the authors hold that the Macaoyuan Group is not comparable with the Neoproterozoic rift successions in South China both in sedimentary characteristics and in ages, and the Macaoyuan Group in the Shennongjia area should be assigned to one of the basement strata beneath the Neoproterozoic rift succession in South China. |
| Keywords: | Maocaoyuan Group tuff SHRIMP U-Pb zircon age Paleo-Proterozoic northern margin of the Yangtze block |
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