Redox Chemistry and Molybdenum Burial in a Mesoproterozoic Lake

K. I. Rico, N. D. Sheldon, T. M. Gallagher, A. Chappaz

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


While marine sediments have been used to constrain a history of redox chemistry throughout the Precambrian, far fewer data have been generated from lakes. With major biological innovations thought to have occurred in Proterozoic lakes, understanding their chemistry is critical for understanding the evolution of eukaryotic life. We use sediment geochemistry to characterize the redox conditions of the Nonesuch Formation (~1.1 Ga) and a modern analogue for the Proterozoic: the Middle Island Sinkhole in Lake Huron (USA). Iron speciation, Mo contents, and Mo-U covariation demonstrate oxic and anoxic—not euxinic—environments, with no clear indicators of enhanced biological productivity in the Nonesuch Formation. Moderate Mo enrichments observed in the Nonesuch Formation are not attributed to euxinia, but instead to an authigenic particulate shuttle. We suggest that the Fe and Mo sediment geochemistry of these lacustrine systems reflect only local water column and sediment burial conditions and not atmospheric oxygenation.

Original languageEnglish
Pages (from-to)5871-5878
Number of pages8
JournalGeophysical Research Letters
Issue number11
StatePublished - Jun 16 2019


  • Proterozoic
  • biogeochemistry
  • molybdenum
  • redox


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