Pyritization of trees from the natural phenomenon Underwater Petrified Forest, Sozopol Bay, Black Sea, Bulgaria

In the Black Sea area between the town of Sozopol and the island of St. Ivan, Bulgaria, dozens of petrified trees are exposed at a depth of 18–20 meters. This forest, probably existing in Miocene in a swampy pond, provides a unique setting to study later fossilization processes. Pyrite, a key mineral involved in the fossilization of organisms, constitutes over 80% of the studied samples and exhibits framboidal and microcrystalline textures, crucial for preserving plant cellular anatomy. Pyritization, occurring in hypoxic or anoxic environments, preserves fine details and prevents structural collapse during lithification. The transformation of marcasite to pyrite under specific conditions highlights dynamic mineralogical processes. X-ray powder diffraction analyses reveal secondary minerals including goethite, jarosite, and szomolnokite, indicating significant post-depositional environmental changes. Understanding these processes is essential for interpreting the fossilising factors that contributed to the formation of the Underwater Petrified Forest, emphasizing the importance of pyritization in paleontological studies.