南华系、莲沱组年龄问题的讨论  

AN UPDATE ON THE CHRONOSTRATIGRAPHY OF THE NANHUAN SYSTEM

作　　者：张启锐[1] 兰中伍[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029

出　　处：《地层学杂志》2016年第3期297-301,共5页Journal of Stratigraphy

基　　金：国家重点基础研究发展计划(No.2013CB835005)

摘　　要：南华系自建立开始，围绕其定义和内涵的争议就一直存在。经过近二十年的研究，分歧逐渐得到弥合，最近，随着莲沱组顶界年龄-714Ma、长安组底界年龄-716Ma、和两界河段（一原渫水河组）顶部年龄-690Ma的精确测定，上述争议得到进一步解决。“国际年代地层表”（2015年版）把成冰系的底界年龄改为720Ma，意味着人们对于南华系（成冰系）的认识取得了进一步的共识，这些对于统一关于南华系的认识十分重要。另外，莲沱组的启始年龄为-800Ma、结束年龄为-714Ma，层位上位于南华系之下。这些年龄的获得也同时引发了一些新问题，值得进一步探讨：如为什么莲沱组的顶界年龄和长安组底界或拱洞组顶界年龄基本上相当？这与人们对于两地古地理、古海拔的认识不协调；关于古城冰期起始年龄的测定，提出了皖浙赣地区的江口冰期地层是否存在、是否完整等问题。Ever since its establishment, the Nanhuan System has been a matter of debate. However, con- sensus has emerged recently as new radiometric ages become available, including -714 Ma ages from the top Liantuo Formation, -716 Ma ages from the basal Chang＇an Formation, and -690 Ma ages from the upper Liangjiehe Member （formerly the Xieshuihe Formation at the Yangjiaping section in northwest Hu- nan Province）. A modification of the base of the Cryogenian System in the 2015 International Chronostrati- graphic Chart helps to reconcile the inconsistencies of Cryogenian chronostratigraphy in different parts of the world and to better understand the Nanhuan System. In the same time, these new ages raise new ques- tions about the Nanhuan System. For example, the stratigraphic relationship between the top Liantuo For- mation and the basal Chang＇an Formation remains uncertain, the Nanhuan paleogeography is poorly un- derstood, the onset of the Gucheng glaciation is not geochronologically constrained, and it is uncertain whether the Jiangkou glacial sequence is complete in the eastern part of the Yangtze Block.

关 键 词：年代地层 国际年代地层表(2015) 同位素年龄 莲沱组 拱洞组 渫水河组 南华系 中国 全球 

分 类 号：P534.3[天文地球—古生物学与地层学]