Isotopes, ice ages, and terminal Proterozoic earth history

  1. Alan J. Kaufman*,
  2. Andrew H. Knoll*,, and
  3. Guy M. Narbonne
  1. *Botanical Museum, Harvard University, Cambridge, MA 02138; and Department of Geological Sciences, Queens University, Kingston, Ontario, K7L 3N6 Canada

Abstract

Detailed correlations of ancient glacial deposits, based on temporal records of carbon and strontium isotopes in seawater, indicate four (and perhaps five) discrete ice ages in the terminal Proterozoic Eon. The close and repeated stratigraphic relationship between C-isotopic excursions and glaciogenic rocks suggests that unusually high rates of organic carbon burial facilitated glaciation by reducing atmospheric greenhouse capacity. The emerging framework of time and environmental change contributes to the improved resolution of stratigraphic and evolutionary pattern in the early fossil record of animals.

Footnotes

  • To whom reprint requests should be addressed. e-mail: aknoll{at}oeb.harvard.edu.

  • Andrew H. Knoll

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