期刊
GEOPHYSICAL RESEARCH LETTERS
卷 46, 期 11, 页码 5871-5878出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2019GL083316
关键词
redox; molybdenum; Proterozoic; biogeochemistry
资金
- National Science Foundation Graduate Student Research Fellowships
- Sokol Foundation
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 (similar to 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.
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