华北北部土城子组时代及中国陆相侏罗-白垩系界线探讨

Ages of the Tuchengzi Formation in northern China and the terrestrial Jurassic-Cretaceous boundary in China

文中简要介绍了华北北部土城子组区域分布、沉积特征和垂向充填序列。针对目前土城子组时代不定的现状,结合近些年来已发表的土城子组的同位素年代学数据,将土城子组年龄限定在154~137Ma。以往对土城子组进行的相关生物地层研究成果与土城子组时代一致。国际地层委员会(ICS)2013年提出将145Ma定为侏罗-白垩系界线年龄,这得到了特提斯喜马拉雅和安第斯地区最新侏罗-白垩系界线研究成果的支持,虽然最终确定这一界线还需更多高精度年代学的研究。再结合土城子组同位素年龄,提出土城子组时代为晚侏罗世—早白垩世,中国陆相侏罗-白垩系界线存在于土城子组内部。国际地层界线及对比,特别是国际J/K界线应通过研究海相生物地层来完成,中国陆相J/K界线的确立应优先服从海相地层及其生物演化所划分的标志与结果。

We here briefly introduce the distribution, sedimentary characteristics and filling sequence of the Tuchengzi Formation in northern North China. On the basis of the uncertainty of the age of the Tuchengzi For mation, we analyzed all the isotopic dating data and constrained the age of Tuchengzi Formation to be 154 - 137 Ma. Previous biostratigraphy research is consistent with the age of Tuchengzi Formation. The International Com- mission on Stratigraphy （ICS） proposed 145 Ma to be the age of Jurassic-Cretaceous boundary in 2013, which is supported by recent studies in the Tethy^Himalaya and Andes, although more high-precision geochronology is still needed for the final establishment. This boundary age suggests that the Tuchengzi Formation is the Late Jurassic-Early Cretaceous in age, and the terrestrial Jurassic-Cretaceous boundary in China exists in the Tuchengzi Formation. The international stratigraphic boundary, especially for the J/K boundary, should be es- tablished by the marine biostratigraphy. The establishment of the J/K boundary in China should give priority to obey the symbol and achievement derived from the marine biostratigraphy and organic evolution.