Chiang Mai University, Thailand

Complex tunnel structures in siderites and garnets from deep sea volcaniclastic sediments and river sediments, respectively, have been observed and interpreted as the result of boring fungi. Synchrotron-Radiation X-ray Tomographic Microscopy (SRXTM) has been used to study the morphology of the mycelium-like tunnel structures that display intricate morphologies including branching, septa, central pore and anastomosis. Fossilized fungal hyphae have been found within the tunnel structures and with the dye Wheat Germ Agglutinin conjugated with Fluorescein Isothiocyanate (WGA-FITC) in combination with fluorescence microscopy chitin has been detected in association with the fossilized hyphae. Chitin is a component in fungal cell walls and is absent in all prokaryotes and thus a good tool to discriminate between eukaryotes and prokaryotes. The material that has been used in this study represents two very different geological settings: 1) Samples of lithified volcaniclastic material of Miocene age that were drilled and collected during Ocean Drilling Program (ODP) Leg 157 outside Gran Canaria in the Atlantic Ocean. 2) Garnets (pyrope and almandine) collected in river sediments from the Phu Fai, Si Sa Ket Province, Khao Wua and Ban Bang Kacha, Chantaburi Province, Ban Bo Rai, Ban Bo Phloi and Ban Nong Bon, Trat Province, Thailand. These two individual studies not only confirm that fungi can produce tunnel structures but also that fungi are capable of doing so under very different geochemical conditions and in very different minerals. Our results indicate that fungi is a powerful geobiological agent and probably of importance for weathering processes of minerals and mobilization of elements. It is also of interest in a paleobiological context since tunnel structures in various minerals and materials like carbonates, silicates and volcanic glass observed through out the fossil record have been attributed to fungal boring but fungi have never been shown, in nature nor in laboratory experiments, to be able to produce tunnel structures.