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Enigmatic origin of the largest-known carbon isotope excursion in Earth’s history

Grotzinger, John P. and Fike, David A. and Fischer, Woodward W. (2011) Enigmatic origin of the largest-known carbon isotope excursion in Earth’s history. Nature Geoscience, 4 (5). pp. 285-292. ISSN 1752-0894.

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Carbonate rocks from the Middle Ediacaran period in locations all over the globe record the largest excursion in carbon isotopic compositions in Earth history. This finding suggests a dramatic reorganization of Earth's carbon cycle. Named the Shuram excursion for its original discovery in the Shuram Formation, Oman, the anomaly closely precedes impressive events in evolution, including the rise of large metazoans and the origin of biomineralization in animals. Instead of a true record of the carbon cycle at the time of sedimentation, the carbon isotope signature recorded in the Shuram excursion could be caused by alteration following deposition of the carbonate sediments, a scenario supported by several geochemical indicators. However, such secondary processes are intrinsically local, which makes it difficult to explain the coincident occurrence of carbon isotope anomalies in numerous records around the globe. Both possibilities are intriguing: if the Shuram excursion preserves a genuine record of ancient seawater chemistry, it reflects a perturbation to the carbon cycle that is stronger than any known perturbations of the modern Earth. If, however, it represents secondary alteration during burial of sediments, then marine sediments must have been globally preconditioned in a unique way, to allow ordinary and local processes to produce an extraordinary and widespread response.

Item Type:Article
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URLURL TypeDescription ReadCube Access
Grotzinger, John P.0000-0001-9324-1257
Fike, David A.0000-0003-2848-0328
Fischer, Woodward W.0000-0002-8836-3054
Additional Information:© 2011 Macmillan Publishers Limited. Published online 17 April 2011. We thank the Agouron Institute and the NASA Astrobiology Institute for support. T. Raub helped with construction of Fig. 2. K. Bergmann supplied the image in Fig. 4b. M. Saltzman is acknowledged for sharing pre-publication composite carbon isotope data used to construct Fig. 1, and C. Verdel and B. Wernicke are thanked for sharing pre-publication data for the Johnnie Formation shown in Fig. 3. L. Author contributions: J.G., D.F. and W.F each contributed by writing the text, drafting the figures and participating in data analysis. These responsibilities were divided equally.
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Agouron InstituteUNSPECIFIED
Subject Keywords:Palaeoclimate and palaeoceanography; Palaeontology
Issue or Number:5
Record Number:CaltechAUTHORS:20110519-132418027
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23737
Deposited By: Ruth Sustaita
Deposited On:19 May 2011 20:54
Last Modified:13 Dec 2019 00:48

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