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地质力学学报:2018,24(5):645-660
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四川盆地陆相侏罗系白垩系界线问题探讨
刘刚1, 董树文1,2
(1.中国地质科学院, 北京 100037;2.南京大学地球科学与工程学院, 江苏 南京 210093)
DISCUSSION ON THE CONTINENTAL JURASSIC-CRETACEOUS BOUNDARY IN THE SICHUAN BASIN
LIU Gang1, DONG Shuwen1,2
(1.Chinese Academy of Geological Sciences, Beijing 100037, China;2.School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, Jiangsu, China)
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投稿时间:2018-01-18    修订日期:2018-08-01
中文摘要: 侏罗系/白垩系界线是国际地层年表中少有几个未定全球界线层型(GSSP)之一。传统上依据菊石类生物将Berriasian阶底界定义为白垩系的底界。国际上西北太平洋Shatsky Rise的Berriasian阶最底部玄武岩岩床的同位素年代学年龄为145 Ma,从而为侏罗系/白垩系界线提供了最接近的年龄估计值。在国际上,地层对比划分大都根据海相地层,中国广泛发育的陆相侏罗系/白垩系,难以与国际标准地层对比。中国四川盆地以陆相生物为标志的界线划分与国际年代地层对比困难,导致对四川盆地陆相侏罗系/白垩系界线问题的认识长期未有更新。根据陆相生物对比结果的同时,结合考虑同位素测年、磁性地层和旋回地层,有望获得良好的效果。基于同位素测年数据和陆相生物对比分析,在遂宁组中发现了最年轻的~120 Ma的碎屑锆石U-Pb年龄,而且该套地层与国际对比的核心证据介形类的研究也有新的发现,表明遂宁组有可能属于白垩系而非原认为的侏罗系。将沙溪庙组和遂宁组作为侏罗系/白垩系过渡地层系统研究,有可能在该套地层内部发现界线标志。
中文关键词: 四川盆地  侏罗系  白垩系  界线  锆石
Abstract:The Jurassic/Cretaceous is one of the boundaries that do not yet have an accepted global boundary definition. The Berriasian stage is traditionally defined as the Cretaceous base according to ammonites. The geochronology age of basalt bedrock at the bottom of the Berriasian stage in Shatsky Rise, Northwest Pacific is 145Ma, which provides the closest estimate age of the Jurassic/Cretaceous boundary. The international stratigraphical division and correlation are based on marine standard, Jurassic and Cretaceous strata in China are mostly of continental strata which are difficult to compare with international standard strata. Therefore, the dominant opinion on Jurassic/Cretaceous boundary in the Sichuan Basin has not been renewed for a long time. Based on a comprehensive analysis of paleontological, geochronologic and paleogeomagnetic studies, good results are expected. The youngest detrital zircon U-Pb age is ~120 Ma, which reflects a depositional age of younger than ~120 Ma.The detrital zircon U-Pb age of Suining Formation shows that this widespread formation should be assigned to the Cretaceous, not the Jurassic. If it is the case, the transition beds of the Jurassic/Cretaceous would be down to Shaximiao Formation and Suining Formation. Based on systematic study, the indicators or markers of the Jurassic/Cretaceous boundary would be obtained from Shaximiao Formation and Suining Formation.
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基金项目:中国地质科学院基本科研业务费项目(YWF201709)
引用文本:
刘刚,董树文.四川盆地陆相侏罗系白垩系界线问题探讨[J].地质力学学报,2018,24(5):645-660DOI:10.12090/j.issn.1006-6616.2018.24.05.065
LIU Gang,DONG Shuwen.DISCUSSION ON THE CONTINENTAL JURASSIC-CRETACEOUS BOUNDARY IN THE SICHUAN BASIN[J].,2018,24(5):645-660DOI:10.12090/j.issn.1006-6616.2018.24.05.065

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