A comparison of the molecular composition of plant and fungal structural biopolymer standards with the organic material in early cretaceous Ontong Java Plateau Tuff

Abstract Earlier investigations have suggested that an extensive deep biosphere with a significant fungal component is present within the sub-oceanic crust. To investigate this further, the organic material in the lithic sections of a sub-oceanic volcaniclastic tuff obtained from the eastern lobe of the Ontong Java Plateau (OJP tuff) were characterised using X-ray photoelectron spectroscopy and thermal hydrolysis and methylation coupled to gas chromatography/mass spectrometry. In the investigation here, the chemical and molecular composition of plant and fungal structural biopolymer standards were characterised using the same techniques and then compared to the organic material from the OJP tuff. This was conducted on untreated material and after hydrous pyrolysis, a process that simulated the physical and thermal decomposition of organic material that occurs during late diagenesis. The characteristics of the organic material in the OJP tuff matched the products of hydrous-pyrolysed chitin. This result suggested that OJP tuff contained organic material that could have been derived from fossilised chitin, implying that the OJP tuff potentially contained the remnants of a microbial community with a fungal component.