Questioning the role of methane in the wake of a snowball Earth: Insights from isotopically anomalous cap dolostone cements with a complex diagenetic history - 2024
Questioning the role of methane in the wake of a snowball Earth: Insights from isotopically anomalous cap dolostone cements with a complex diagenetic history
Cui, Huan; Kitajima, Kouki; Orland, Ian J.et al.
2024 • In Geochimica et Cosmochimica Acta, 364, p. 195 - 210
Authigenic carbonate; Cap dolostones; Methane clathrate; Methane seeps; Secondary ion mass spectrometry; Geochemistry and Petrology
Abstract :
[en] Methane has been widely regarded as an important source of greenhouse gas that modulated Earth's paleoclimate. Notably, it has been proposed that a massive release of methane via clathrate destabilization may have played a critical role during and/or in the immediate aftermath of the Marinoan deglaciation. One key piece of supporting evidence for this hypothesis comes from the isotopically anomalous (δ13Ccarb < –30 ‰) methane-derived authigenic calcite (MDAC) cements within post-Marinoan cap dolostones in South China. However, the origin of these MDAC cements remains hotly contested, including a clumped isotope study that reinterpreted them as resulting from late hydrothermal fluids. To further evaluate these critical yet controversial cements, a detailed investigation by secondary ion mass spectrometry (SIMS) was conducted. Here we report the largest range of δ13Ccarb values (–53.1 ‰ to +6.3 ‰) yet measured in Precambrian carbonates. Our study shows that the MDAC cements are post-depositional, void-filling, and rich in Mn. Importantly, integrated petrographic and SIMS results consistently show that MDAC cements post-date disrupted dolomite laminae that bear surprisingly positive δ13Ccarb values up to +6.3 ‰. This is the first report that authigenic carbonates with positive δ13Ccarb signals are found within post-Marinoan cap dolostone. Although the precise age of these authigenic carbonates remains ambiguous, integrated chemostratigraphic and SEM-SIMS results suggest that the dolomite laminae formed after the deposition of the uppermost cap dolostone interval, when the seawater δ13C had already evolved to positive values; and the MDAC formed even later. The dolomite laminae and MDAC cements, therefore, represent distinct post-depositional, exogenous, diagenetic carbon signals that are irrelevant to the deglaciation. Our new results challenge the hypothesis that methane played a central role at the end of or in the immediate aftermath of the Marinoan glaciation. Rather, the infiltration of methane-bearing fluids within cap dolostones could have occurred much later.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Cui, Huan ; Department of Geosciences, Mississippi State University, United States ; Department of Geoscience, University of Wisconsin-Madison, Madison, United States
Kitajima, Kouki; Department of Geoscience, University of Wisconsin-Madison, Madison, United States
Orland, Ian J. ; Department of Geoscience, University of Wisconsin-Madison, Madison, United States ; Wisconsin Geological and Natural History Survey, University of Wisconsin-Madison, Madison, United States
Baele, Jean-Marc ; Université de Mons - UMONS > Faculté Polytechniqu > Service de Géologie fondamentale et appliquée
Denny, Adam; Department of Geoscience, University of Wisconsin-Madison, Madison, United States ; Pacific Northwest National Laboratory, Richland, United States
Spicuzza, Michael J.; Department of Geoscience, University of Wisconsin-Madison, Madison, United States
Fournelle, John H.; Department of Geoscience, University of Wisconsin-Madison, Madison, United States
Goderis, Steven ; Archaeology, Environmental Changes and Geo-Chemistry Group, Vrije Universiteit Brussel, Brussels, Belgium
de Winter, Niels J.; Archaeology, Environmental Changes and Geo-Chemistry Group, Vrije Universiteit Brussel, Brussels, Belgium ; Department of Earth Sciences, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
Valley, John W. ; Department of Geoscience, University of Wisconsin-Madison, Madison, United States
Language :
English
Title :
Questioning the role of methane in the wake of a snowball Earth: Insights from isotopically anomalous cap dolostone cements with a complex diagenetic history
National Science Foundation U.S. Department of Energy College of Engineering, University of Wisconsin-Madison NASA Astrobiology Institute Vrije Universiteit Brussel
Funding text :
This study was supported by the NASA Astrobiology Institute ( NNA13AA94A ) at UW-Madison. The WiscSIMS Lab was supported by NSF (EAR-1658823, -2004618) and UW-Madison. JWV was also supported by NSF (EAR-1524336) and DOE (DE-FG02-93ER14389). The XRF lab was supported by VUB strategic research funding. This paper benefits from constructive and detailed reviews by Paul F. Hoffman (Harvard & Victoria), Eva E. Stüeken (St Andrews), and two other anonymous reviewers. The authors thank Associate Editor Eva E. Stüeken and Executive Editor Jeffrey G. Catalano (WUSTL) for their efficient handling of this manuscript. Huan Cui dedicates this paper to his former academic advisor Dr. Ping Guan (Professor Emeritus of Sedimentary Geology), who recently retired from the Department of Geology at Peking University, for the lively and respectful mentorship and the practical hands-on research experience that HC received from 2008 to 2011 in different oil fields in China.The authors want to sincerely thank Ganqing Jiang (UNLV) for sharing the samples that were previously studied by Jiang et al. (2006a) and offering constructive and open-minded comments on this study. We also thank Brian Hess, Noriko Kita, James Kern, Maciej Śliwiński, and Akizumi Ishida for assistance in sample preparation and SIMS analysis at UW-Madison; Bil Schneider (UW-Madison), Stephan Borensztajn and Bénédicte Ménez (IPGP) for assistance in the SEM laboratories; Yiheng Wu for assistance in compiling the supplemental materials. Although the views are those of the authors, many small questions or confusions have been clarified via kind discussions with the following colleagues over the years. They are Chuanming Zhou (NIGPAS), Yongbo Peng (NJU), Huiming Bao (NJU), Shuhai Xiao (VT), Taiyi Luo (IGCAS), Tian Gan (UMD), Xianguo Lang (CDUT), Jing Huang (IOCAS), Fei Li (SWPU), Zhou Wang (CUG-Wuhan), Zhongwu Lan (IGGCAS), Magali Bonifacie (IPGP), and Chaojin Lu (Miami). This study was supported by the NASA Astrobiology Institute (NNA13AA94A) at UW-Madison. The WiscSIMS Lab was supported by NSF (EAR-1658823, -2004618) and UW-Madison. JWV was also supported by NSF (EAR-1524336) and DOE (DE-FG02-93ER14389). The XRF lab was supported by VUB strategic research funding. This paper benefits from constructive and detailed reviews by Paul F. Hoffman (Harvard & Victoria), Eva E. Stüeken (St Andrews), and two other anonymous reviewers. The authors thank Associate Editor Eva E. Stüeken and Executive Editor Jeffrey G. Catalano (WUSTL) for their efficient handling of this manuscript. Huan Cui dedicates this paper to his former academic advisor Dr. Ping Guan (Professor Emeritus of Sedimentary Geology), who recently retired from the Department of Geology at Peking University, for the lively and respectful mentorship and the practical hands-on research experience that HC received from 2008 to 2011 in different oil fields in China.
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