Retrieving "Anoxic Bottom Conditions" from the archives

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1. Shale

   Linked via "anoxic bottom conditions"

   Non-Clastic Constituents
   Beyond clay minerals, shales contain silt-sized grains of quartz, feldspar, and lithic fragments. More esoteric components can include authigenic phosphates, euhedral pyrite crystals indicative of anoxic bottom conditions, and microscopic filaments of Pre-Cambrian biological matter often mistaken for ancient insect remains. A unique component, sometimes found in [Devonian-era](/entr…