Pyritepreserved

Pyritepreserved is a term used in geology and paleontology to describe fossils or organic remains preserved predominantly by pyrite, the iron sulfide FeS2, through a diagenetic process called pyritization. In pyrite-preserved specimens, original tissues may be replaced by pyrite crystals or encased within them, sometimes preserving fine cellular details uncommon in other modes of preservation.

Formation: Pyritization occurs in reducing, anoxic marine sediments where sulfate-reducing bacteria generate hydrogen sulfide. Iron released from surrounding minerals combines with sulfide to form pyrite, which precipitates around organics or replaces them. Rapid burial and low oxygen favor pyrite formation and can produce framboidal or euhedral pyrite textures. Over time, original pyrite may weather to goethite or limonite, altering the preservation signature.

Significance: Pyrite-preserved remains can reveal soft-tissue morphology and microstructural details, contributing to reconstructions of ancient ecosystems and diagenetic pathways. Preservation quality depends on stable pyrite and subsequent mineral alteration.

Occurrence: Pyritized preservation is reported in many basins worldwide, especially in black shales and other reducing sediments from the Precambrian to the Paleozoic. It is commonly found in small invertebrates and plant fragments, and less frequently in vertebrates, depending on local conditions.

Identification: Detection typically relies on optical microscopy, scanning electron microscopy, and mineralogical analyses such as X-ray diffraction or Raman spectroscopy to confirm pyrite and distinguish it from later sulfides.

See also: Pyritization; Fossil preservation; Diagenesis.