ABSTRACT

Homologous series of low molecular weight monocarboxylic acids (C₂ to C₁₂) and γ-lactones (C₅ to C₁₂) were detected in Miocene to Pliocene sediments of Shinjo basin. Abundances of the monocarboxylic acids are 10^-6 to 10^-8g/g, and those of the γ-lactones are 10^-7 to 10^-9 g/g. The monocarboxylic acids show the unique predominance of nonanoic acid over octanoic and decanoic acids. The γ-lactones show a predominance of hexanoic lactone in most of the sediments. No δ-lactones were detected in the sediments. It seems that the two classes of organic compounds were converted from common precursors, namely cis-9 unsaturated fatty acids, during the early stages of sediment diagenesis.