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Continental weathering intensity during the termination of the Marinoan Snowball Earth: Mg isotope evidence from the basal Doushantuo cap carbonate in South China
Li, Jian1,2; Hao, Cuiguo1,2; Wang, Zhihong1,2; Dong, Lin3; Wang, Yiwu3; Huang, Kang-Jun4; Lang, Xianguo5; Huang, Tianzheng3; Yuan, Honglin4; Zhou, Chuanming6; Shen, Bing3
2020-08-15
Source PublicationPALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
ISSN0031-0182
Volume552Pages:12
Abstract

The Neoproterozoic global glaciations (720-635 Ma) represent the most severe icehouse climatic conditions in Earth's history, collectively known as the 'Snowball Earth events'. The 'Snowball Earth' hypothesis (Hoffman et al. 1998) proposed that the termination of the global glaciation was driven by the extremely high atmospheric pCO(2) level (300 times of present atmospheric level, PAL) that was accumulated during the global glaciation by volcanic degassing for tens of million years. Because of extremely high temperature, the deglaciation might associate with intense continental weathering that brought abundant bicarbonate and alkaline earth metals (Mg, Ca) to the ocean, resulting in the rapid precipitation of cap carbonate all over the world. Thus, cap carbonate precipitation marks the termination of global glaciation. The deglacial intense continental weathering has been recently supported by Mg isotopes. However, the Mg isotope data also indicate that the deglaciation might have significantly predated the cap carbonate precipitation, and limited data suggest that the weathering intensity was already low during the cap carbonate precipitation. In order to further test whether the cap carbonate precipitation was associated with low weathering intensity, here we analyzed Mg isotopic composition of siliciclastic component (delta Mg-26(sil)) of the Doushantuo cap carbonate in the Yangtze Block, South China. Four cap carbonate sections (the Tongle (TL) drill core, the Fanyang (FY) section, the Wuluo (WL) drill core, and the Jiulongwan (JLW) section), spanning from shelf to basin environments, were analyzed. delta Mg-26(sil) ranges from -0.43 parts per thousand to +0.39 parts per thousand (n = 10), from -0.31 parts per thousand to +0.48 parts per thousand (n = 9), from -0.06 parts per thousand to +0.10 parts per thousand (n = 7), and from -1.42 parts per thousand to -0.03 parts per thousand (n = 8) for the JLW, FY, WL, and TL samples, respectively. There are negative correlations between Mg/Al and delta Mg-26(sil) in JLW, WL, and TL. The geochemical data indicate that the variation of delta(26)Mg(sil )might be attributed to authigenic clay formation during the cap carbonate precipitation. The binary mixing model indicates that the isotopic compositions of terrestrial clays range from 0 parts per thousand to +0.3 parts per thousand, comparable to the values of modern soil clays but significantly lower than the values of the upper Nantuo Formation (up to similar to + 0.90 parts per thousand), suggesting the moderate to low weathering intensity during the cap carbonate deposition. Our study suggests low atmospheric pCO(2) level during cap carbonate precipitation probably due to the consumption by intense continental weathering

KeywordGlobal glaciation Doushantuo formation Yangtze block Atmospheric CO2 Neoproterozoic Cryogenian
DOI10.1016/j.palaeo.2020.109774
Indexed BySCI
Language英语
WOS KeywordGLACIATION EVIDENCE ; YANGTZE BLOCK ; OCEAN ; SEDIMENTARY ; DEPOSITION ; CALCIUM ; BASIN ; FRACTIONATION ; CONSTRAINTS ; DOLOSTONES
Funding ProjectNational Natural Science Foundation of China[41672334] ; National Natural Science Foundation of China[41772359]
WOS Research AreaPhysical Geography ; Geology ; Paleontology
WOS SubjectGeography, Physical ; Geosciences, Multidisciplinary ; Paleontology
WOS IDWOS:000538140400009
Funding OrganizationNational Natural Science Foundation of China
PublisherELSEVIER
Citation statistics
Document Type期刊论文
Identifierhttp://ir.nigpas.ac.cn/handle/332004/31969
Collection中国科学院南京地质古生物研究所
Corresponding AuthorDong, Lin
Affiliation1.PetroChina Res Inst Petr Explorat & Dev, Beijing 100083, Peoples R China
2.CNPC, Key Lab Gas Reservoir Format & Dev, Langfang 065007, Peoples R China
3.Peking Univ, Sch Earth & Space Sci, Key Lab Orogen Belts & Crustal Evolut, MOE, Beijing 100871, Peoples R China
4.Northwest Univ, Dept Geol, Shaanxi Key Lab Early Life & Environm, Xian 710069, Peoples R China
5.Chengdu Univ Technol, Inst Sedimentary Geol, Chengdu 610059, Peoples R China
6.Chinese Acad Sci, Ctr Excellence Life & Paleoenvironm, Nanjing Inst Geol & Palaeontol, State Key Lab Palaeobiol & Stratig, Nanjing 210008, Peoples R China
Recommended Citation
GB/T 7714
Li, Jian,Hao, Cuiguo,Wang, Zhihong,et al. Continental weathering intensity during the termination of the Marinoan Snowball Earth: Mg isotope evidence from the basal Doushantuo cap carbonate in South China[J]. PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY,2020,552:12.
APA Li, Jian.,Hao, Cuiguo.,Wang, Zhihong.,Dong, Lin.,Wang, Yiwu.,...&Shen, Bing.(2020).Continental weathering intensity during the termination of the Marinoan Snowball Earth: Mg isotope evidence from the basal Doushantuo cap carbonate in South China.PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY,552,12.
MLA Li, Jian,et al."Continental weathering intensity during the termination of the Marinoan Snowball Earth: Mg isotope evidence from the basal Doushantuo cap carbonate in South China".PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY 552(2020):12.
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