Fossil worm tubes from the presumed cold-seep carbonates of the Miocene Hayama Group, Central Miura Peninsula, Japan

Abstract Fossil worm tubes were collected from the Hayama Group, Miura Peninsula, Japan, together with abundant fossils of Calyptogena-Acharax clams. The fossil worm tubes were well preserved and coated with milky white amorphous silica. Most of the tubes were 1-3 mm in diameter, and up to 10 cm in length. Worm tubes were found in siltstone and limestone, and formed network-like assemblages. Elemental mapping on the tube cross-sections revealed the localization of sulfur, zinc and iron at the worm tubes, which suggests that sulfur-related metabolism and deposition occurred in association with the worm tubes. High resolution analysis revealed the localization of zinc-sulfur (sphalerite, ZnS) on the tubes, while iron-sulfur (pyrite, FeS₂) was localized at the center of the tubes. The spatially separate sphaleritization and pyritization imply that epiphytic and endosymbiotic microorganisms perform different sulfur metabolisms, such as sulfate-reduction and sulfide-oxidation.