Early Earths Sulfidic Ocean Conditions

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Iron speciation data from the late Archean Mount McRae Shale indicates the presence of euxinic (anoxic and sulfidic) conditions in the water column approximately 2.5 billion years ago. Sulfur isotope analysis suggests that these euxinic conditions were likely driven by increased oceanic sulfate concentrations, resulting from the weathering of continental sulfide minerals in an atmosphere with minimal photosynthetic oxygen. The variability in organic matter flux may have restricted euxinic conditions to specific areas within the water column, particularly along the basin margin. These findings imply that euxinic conditions were prevalent across various spatial and temporal scales prior to and following the Paleoproterozoic rise in atmospheric oxygen, revealing a complex and variable deep ocean chemistry during early Earth’s history. This underscores the notion that early Earth was vastly different from the current oxic biosphere, highlighting the evolutionary timeline of metazoans as relatively recent in the planet’s history.
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http://www.sciencemag.org/cgi/content/abstract/326/5953/713

Iron speciation data for the late Archean Mount McRae Shale provide evidence for a euxinic (anoxic and sulfidic) water column 2.5 billion years ago. Sulfur isotope data compiled from the same stratigraphic section suggest that euxinic conditions were stimulated by an increase in oceanic sulfate concentrations resulting from weathering of continental sulfide minerals exposed to an atmosphere with trace amounts of photosynthetically produced oxygen. Variability in local organic matter flux likely confined euxinic conditions to midportions of the water column on the basin margin. These findings indicate that euxinic conditions may have been common on a variety of spatial and temporal scales both before and immediately after the Paleoproterozoic rise in atmospheric oxygen, hinting at previously unexplored texture and variability in deep ocean chemistry during Earth’s early history.
 
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Xnn said:
http://www.sciencemag.org/cgi/content/abstract/326/5953/713

Another reason as to why the early Earth was an alien planet compared to our oxic biosphere era. We're really only latecomers to this planet - and by 'we' I mean all metazoans.
 

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