Overall, this is consistent with observations that fine-grained, siliciclastic sedimentary rocks are the primary host for both pyrite framboids ( 12) and pyrite nodules/concretions ( 37). 6%), limestones, dolomites and cherts (ca. Other pyrite framboidвЂ“and nodule/concretion-bearing rocks include pure sandstones and conglomerates (ca. Approximately 83% of the pyrite framboidвЂ“ and nodule/concretion-bearing rocks are described as shale, mudstone, argillite, or other equivalent fine-grained rock types, including interbedded variants. 83%) of pyrite framboidвЂ“ and nodule-bearing rocks are siliciclastic and dominantly fine-grained (fig. 1B) adjusts for long-term drift in the record relating to plate tectonic regulation of basin type and extent and therefore, by extension, the types of sediments preserved ( 36). Normalization of the framboid and nodule record to all pyrite-bearing metasedimentary and sedimentary rocks ( Fig. A total of 10,320 phrases were matched to 1794 unique stratigraphic names, including 140 framboid bearing and 110 pyrite nodule or concretion bearing (here simplified as вЂњnodule bearingвЂќ), defining a temporal record of pyrite-bearing metasedimentary and sedimentary rocks ( Fig. The algorithm matches phrases (such as вЂњpyrite noduleвЂќ) extracted from the xDD library (10,661,918 documents at the time of analysis) to stratigraphic names recorded in the Macrostrat stratigraphic database ( 28вЂ“ 30), with an effective accuracy of at least 87% (see the Supplementary Materials for accuracy estimates) ( 31). Text mining was implemented using the GeoDeepDive (now known as xDD) digital library and machine-reading system ( 26) coupled to an algorithm that decomposes sentences into speech and linguistic components using Stanford natural language processing (NLP fig. By contrast, nodular and concretionary pyrite precipitation is a relatively slow process that occurs under advective or stagnant (poly)sulfidic conditions ( 12), conditions that tend to exist during nonвЂ“steady-state fluid dewatering ( 18) of sulfidic sediments near the seabed. These conditions may exist in the water column and/or in pore waters, where sulfide typically persists for several centimeters to meters below seabed ( 14вЂ“ 17), depending on a variety of factors including sulfate and OM availability. Pyrite framboids precipitate relatively fast, under diffusion-limited conditions and from fluids at the supersaturation limit with respect to FeS or FeS 2 ( 12, 13). Sedimentary pyrite formation occurs via reaction between reduced Fe and S, a process that is typically catalyzed in the marine environment during degradation of organic matter (OM) by sulfate-reducing microbes ( 11).

The underlying driver(s) for the pyrite types are unresolved but plausibly includes the ambient seawater inventory, precipitation kinetics, and the (co)location of organic matter degradation coupled to sulfate reduction, iron (oxyhydr)oxide dissolution, and pyrite precipitation.ДЄ prominent factor in terms of the response of the marine system to changes in ocean redox concerns the formation of pyrite (FeS 2), which is commonly preserved in a variety of forms dictated by the precise local conditions encountered during its formation. This analysis delineates the prevalent anoxic basin states from the Archaean to present day, which are associated with diagnostic combinations of five types of syngenetic pyrite. We combine machine-reading techniques, applied over a large library of published literature, with statistical analysis of element concentrations in databases of sedimentary pyrite and bulk sedimentary rocks to generate a scaled analysis spanning the majority of EarthвЂ™s history. Here, we provide a temporal record of bottom and pore water redox conditions by analyzing the temporal distribution and chemistry of sedimentary pyrite. The redox structure of the water column in anoxic basins through geological time remains poorly resolved despite its importance to biological evolution/extinction and biogeochemical cycling.

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