中国科学院南京地质古生物研究所机构知识库

Palaeoproterozoic global glaciation (similar to 2.3 Ga) may have been the first "snowball" Earth event in Earth history. North China has well-exposed sedimentary deposits of this time period with minimal postdepositional alteration. Sedimentary evidence of a glaciation event has been lacking, however. Here we analyzed carbon isotope composition of the Paleoproterozoic Hutuo Group (2.5-2.2 Ga) in the Wutai Mountain area, Shanxi Province, North China. Our data show, in an older to younger chronostratigraphic order, (1) positive delta(13)C(carb) values in the Dashiling Formation of the Doucun Subgroup (3.2 parts per thousand to 1.0 parts per thousand, VPDB); (2) a decrease in delta(13)C(carb) values from the Wenshan Formation to the middle Daguandong Formation (from 2.0 parts per thousand to -1.2 parts per thousand), during which time the occurrence of stromatolites declined; (3) a pronounced negative excursion in the upper Daguandong Formation, at the boundary of the Daguandong and Huaiyincun formations (from 1.4 parts per thousand to -3.3 parts per thousand), where stromatolites disappeared; and (4) a gradual increase of delta(13)C(carb) values in the Beidaxing and Tianpengnao formations (from -1.2 parts per thousand to 1.4 parts per thousand), during which time stromatolites returned. We argue that the negative carbon isotope excursion recorded from the Jian'ancun Formation to the middle Daguandong Formation of the Hutuo Group may have been North China's response to the Palaeoproterozoic global glaciation.