ABSTRACT

Twenty six polycyclic aromatic hydrocarbons (PAHs) from naphthalene to coronene were found in the K/T boundary sediments at Kawaruppu, Hokkaido, Japan and their concentrations were estimated except for naphthalene. Another 28 PAHs were found qualitatively. The total concentration of those 25 PAHs (except naphthalene) in each sediment was in the range of 2.3 to 11.4 nmol g^-1 and showed no specific feature for the boundary claystone or for sediments above and below it. Individual PAHs were present at the level of sub-nmol g^-1 or less. Higher concentrations in the sediments within the claystone than those above and below it were observed for parent (i.e., non-alkylated) tetracyclic PAHs and to a certain extent larger peri-condensed parent PAHs. It is not likely that the higher concentrations within the claystone were due to the 65 million year diagenesis because of roughly constant ratios of β- to α-alkylated PAHs in the sediments above, within and below the boundary claystone. The observation may indicate a possible combustion origin of those PAHs within the boundary claystone, although evidence at Kawaruppu is not so strong as at Stevns Klint, Gubbio and Woodside Creek.