Anomalous negative excursion of carbon isotope in organic carbon after the last Paleoproterozoic glaciation in North America

[1] Early Paleoproterozoic time (2.5-2.0 Ga) spanned a critical phase in Earth's history, characterized by repeated glaciations and an increase in atmospheric oxygen (the Great Oxidation Event (GOE)). Following the last and most intense glaciation of this period, marine carbonates record a larg...

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Bibliographic Details
Main Authors: Yasuhito Sekine, Eiichi Tajika, Naohiko Ohkouchi, Nanako O Ogawa, Kazuhisa Goto, Ryuji Tada, Shinji Yamamoto, Joseph L Kirschvink, Y Sekine, E Tajika, N Ohkouchi, N O Ogawa, K Goto, R Tada, S Yamamoto, J L Kirschvink
Other Authors: The Pennsylvania State University CiteSeerX Archives
Format: Text
Language:English
Published: 2010
Subjects:
Methane hydrate
Online Access:http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1045.1614
http://web.gps.caltech.edu/%7Ejkirschvink/pdfs/Sekine_G3_PaleoproterozoicMethane2010.pdf
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Summary:[1] Early Paleoproterozoic time (2.5-2.0 Ga) spanned a critical phase in Earth's history, characterized by repeated glaciations and an increase in atmospheric oxygen (the Great Oxidation Event (GOE)). Following the last and most intense glaciation of this period, marine carbonates record a large positive excursion of d 13 C value (termed the "Lomagundi event") between about 2.2 and 2.1 Ga coinciding with the global appearances of red beds and sulfates, which suggest an accumulation of high levels of atmospheric oxygen. Here we report the discovery of large negative excursions of d 13 C in organic matter (down to −55‰) from quartzose sandstones (of the Marquette Range and the Huronian Supergroups, North America) intermediate in age between the last Paleoproterozoic glaciation and the possible onset of the Lomagundi event. The negative excursion is concomitant with the appearance of intensely weathered quartzose sandstones, which may represent hot and humid conditions. There are some interpretations that potentially explain the negative excursions: (1) redeposition of older 13 C-depleted kerogen, (2) later post-depositional infiltration of oil, (3) active methane productions by methanogens in shallow-marine environments, or (4) dissociation of methane hydrate. If the latter two were the case, they would provide clues for understanding the environmental change connecting the intense glaciation and an increase in oxygen.

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