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GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L05202, doi:10.1029/2003GL018802, 2004

Biotic enhancement of weathering, atmospheric oxygen and carbon dioxide in the Neoproterozoic

Timothy M. Lenton

Centre for Ecology and Hydrology, Bush Estate, Penicuik, UK


Andrew J. Watson

School of Environmental Sciences, University of East Anglia, Norwich, UK


Abstract

It has been suggested that biological colonization of the land surface began in the Neoproterozoic 1000–544 million years ago (Ma). We hypothesize that this colonization involved selective weathering of P from rocks, as well as an amplification of overall weathering rates. We show that two recent models, despite differences in the feedback mechanisms represented, predict that an increase in the weathering flux of P to the ocean would have caused a rise in atmospheric O2 in the Neoproterozoic. This in turn may have provided a necessary condition for the evolution of animals with hard skeletons seen in the ‘Cambrian explosion’. Increased weathering of silicate rocks would also have caused a decline in atmospheric CO2, which could have been a causal factor in the Neoproterozoic glaciations.

Received 9 October 2003; accepted 10 February 2004; published 10 March 2004.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0330 Atmospheric Composition and Structure: Geochemical cycles; 1886 Hydrology: Weathering (1625); 4805 Oceanography: Biological and Chemical: Biogeochemical cycles (1615); 9619 Information Related to Geologic Time: Precambrian.

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Citation: Lenton, T. M., and A. J. Watson (2004), Biotic enhancement of weathering, atmospheric oxygen and carbon dioxide in the Neoproterozoic, Geophys. Res. Lett., 31, L05202, doi:10.1029/2003GL018802.