[B-PT03] Biomineralization and Geochemistry of Proxies

[BPT03-06] Aromatic furans in sedimentary rocks and their origin

*Masashi A. Ikeda¹, Takuto Ando², Ken Sawada¹ (1.Department of Earth and Planetary Sciences, Faculty of Science, Hokkaido University, 2.Graduate School of International Resource Sciences, Akita University)

Keywords:aromatic furans, biomarker, Permian-Triassic boundary

Aromatic furan compounds such as dibenzofurans have been detected in sedimentary rocks from a wide range of periods. These compounds are considered as terrigenous organic matter, but their origins are still debated. In particular, remarkably high abundances of aromatic furans have been reported at the mass extinction in the end-Permian (P/T boundary). Two hypotheses for the events were proposed; 1) a major collapse event in terrestrial ecosystems (Sephton et al., 2005; Fenton et al., 2007; Wang & Visscher, 2007) and 2) pioneer species and decomposers such as lichens and fungi flourished (Watson et al., 2005; Sawada et al., 2012). The former is assumed to originate from the lignin of higher plants and polysaccharides of terrestrial soils, and is discussed based on the results of catalytic combustion experiments on the formation of dibenzofurans as well as the comparison with the other terrigenous organic matter. On the other hand, the latter is the suggestion originating from secondary metabolites of lichens, which are known to produce a variety of dibenzofuran derivatives, and that various aromatic furan compounds in sedimentary rocks might be directly produced by the lichens. Sephton et al. (2009) reported the detection of aromatic furans similar in composition to those obtained in the P/T boundary in pyrolysis products of Reduviasporonites found in strata dominated by fungal remains reported in the P/T boundary, supporting the possibility that these fungal species were related. In addition, artificial thermal maturation experiments (e.g., Watanabe, 2000) demonstrated that the dibenzofurans were formed from cellulose, lignin, and sugars by maturation, but no alkyl dibenzofuran compounds were formed. These facts suggested that high abundances of aromatic furans in the sediments along the P/T boundary could be originated by specific aromatic furan producers.
This presentation will review the biosynthesis in living organisms such as lichens, simulations of thermal maturation, the detection of aromatic furans in Greenland Mesoproterozoic sedimentary rocks as reported by Ikeda et al. (2022), and discuss the potential of aromatic furans in sedimentary rocks as biomarkers for the earth’s life history study.