Letter | Published:

A palaeotemperature curve for the Precambrian oceans based on silicon isotopes in cherts

Nature volume 443, pages 969972 (26 October 2006) | Download Citation



The terrestrial sediment record indicates that the Earth’s climate varied drastically in the Precambrian era (before 550 million years ago), ranging from surface temperatures similar to or higher than today’s to global glaciation events1. The most continuous record of sea surface temperatures of that time has been derived from variations in oxygen isotope ratios of cherts (siliceous sediments)2, but the long-term cooling of the oceans inferred from those data3,4,5 has been questioned because the oxygen isotope signature could have been reset through the exchange with hydrothermal fluids after deposition of the sediments6. Here we show that the silicon isotopic composition of cherts more than 550 million years old shows systematic variations with age that support the earlier conclusion of long-term ocean cooling and exclude post-depositional exchange as the main source of the isotopic variations. In agreement with other lines of evidence1,7, a model of the silicon cycle in the Precambrian era shows that the observed silicon isotope variations imply seawater temperature changes from about 70 °C 3,500 million years ago to about 20 °C 800 million years ago.

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We thank P. Knauth for constructive and critical reviews, which greatly helped in clarifying the text with regard to the qualitative significance of the thermometric equations proposed for silicon isotopes. We thank W. Schopf, S. Awramik, P. Knauth and the late S. Epstein for providing an unlimited and disinterested access to the most representative samples of their own collections. Author Contributions Both authors contributed equally to this work.

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  1. Muséum National d'Histoire Naturelle, CNRS LEME NanoAnalyses, UMS 2679, 57 rue Cuvier, 75005 Paris, France

    • François Robert
  2. Centre de Recherches Pétrographiques et Géochimiques, CRPG-CNRS BP20, 54501 Vandoeuvre-lès-Nancy, France

    • Marc Chaussidon


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Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

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Correspondence to François Robert.

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