Molybdenum Isotope Evidence for Widespread Anoxia in Mid-Proterozoic Oceans.
Arnold, G. L. 1*; Anbar, A. D. 1,2; Barling, J. 1+; Lyons, T. W. 3
[Report]
Science.
304(5667):87-90, April 2, 2004.
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How much dissolved oxygen was present in the mid-Proterozoic oceans between 1.8 and 1.0 billion years ago is debated vigorously. One model argues for oxygenation of the oceans soon after the initial rise of atmospheric oxygen ~2.3 billion years ago. Recent evidence for H2S in some mid-Proterozoic marine basins suggests, however, that the deep ocean remained anoxic until much later. New molybdenum isotope data from modern and ancient sediments indicate expanded anoxia during the mid-Proterozoic compared to the present-day ocean. Consequently, oxygenation of the deep oceans may have lagged that of the atmosphere by over a billion years.
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