Distribution of polycyclic aromatic hydrocarbons in the K/T boundary sediments at Kawaruppu, Hokkaido, Japan.

Abstract

, JapanTwenty 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 /3 to a-alkylated PAHs in the sediments above, within and below the boundary claystone. The observation may indicate a possible com bustion origin of those PAHs within the boundary claystone, although evidence at Kawaruppu is not so strong as at Stevns Klint, Gubbio and Woodside Creek.

Thiophenes in the Cretaceous/Tertiary boundary sediments at Kawaruppu, Hokkaido, Japan.

“…This period is too short to make a significant difference in the ratio between the top and bottom sediments of 65 million years old. A similar type result was reported for the ratios of β-to α-alkylated PAHs, such as 2-to 1-methylnaphthalene, 2-to 1-methylphenanthrene and 3-to 1-methylphenanthrene, which were found to be roughly constant in the Kawaruppu sediments (Mita and Shimoyama, 1999b). Therefore, it is likely that the 65 million year diagenesis has taken place evenly over the sediments above, within, and below the boundary claystone for the DBTs as well as the PAHs.…”

“…The depth profiles of these polynuclear aromatic thiophenes are quite different from that of the C 25 HBI thiophene and do not show an event directly related to the massive extinction. Furthermore, the distributions of the polynuclear aromatic thiophenes are not consistent with those of total and individual PAHs (Mita and Shimoyama, 1999b), indicating that the formation pathways of those thiophenes were likely different from those of the PAHs in the sediments. A portion of the PAHs within the boundary claystone is considered to be of combustion origin (Mita and Shimoyama, 1999b).…”

“…In this connection, organic geochemical studies on the Cretaceous/Tertiary (K/T) boundary sediments have found evidence for both extraterrestrial organic compounds (Zhao and Bada, 1989) and wildfires triggered by the bolide impact (Wolbach et al, ously, organic geochemical studies of amino acids (Mita et al, 1996) and dicarboxylic acids (Mita et al, 1998) in the sediments suggested the possibility of both extraterrestrial as well as terrestrial sources of these compounds. Characteristic distributions of aliphatic hydrocarbons (Mita and Shimoyama, 1999a), and polycyclic aromatic hydrocarbons (PAHs) (Mita and Shimoyama, 1999b) in the sediments were reported in relation to the massive extinction and wildfires, respectively. Other published studies of the sediments dealt with planktonic foraminifera Kaiho, 1992), palynomorphs , sulfur isotopes (Kajiwara and Kaiho, 1992) and Ir accumulation and clay minerals (Tasaki et al, 1992).…”

Maleimides in the Cretaceous/Tertiary boundary sediments at Kawaruppu, Hokkaido, Japan.

“…In the present study we analyzed free and bound maleimides in the K/T boundary sediments at Kawaruppu in order to obtain another example illustrating the utility of maleimides as biomarkers, as well as to examine maleimide distribution in a sedimentary sequence differing in maturity from that of the Shinjo sediments. Previous studies indicated that the 65 million year diagenesis has taken place evenly over the sediments throughout the sequence (Mita and Shimoyama, 1999a;Katsumata and Shimoyama, 2001). Organic geochemical studies of amino acids (Mita et al, 1996) and dicarboxylic acids (Mita et al, 1998) in the sediments were discussed as to the possibility of the presence of extraterrestrial organic compounds as well as terrestrial ones.…”

“…Organic geochemical studies of amino acids (Mita et al, 1996) and dicarboxylic acids (Mita et al, 1998) in the sediments were discussed as to the possibility of the presence of extraterrestrial organic compounds as well as terrestrial ones. Characteristic distributions of aliphatic hydrocarbons (Mita and Shimoyama, 1999b) and polycyclic aromatic hydrocarbons (PAHs) (Mita and Shimoyama, 1999a) in the sediments were reported and related to the massive extinction and wildfires, respectively.…”