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

Abstract

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, FeS 2 ) 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.