Twenty two steranes and 17 triterpanes were detected in the Cretaceous-Tertiary (K/T) boundary sediments at Kawaruppu, Hokkaido, Japan. These steranes and triterpanes were detected at a concentration level of 0.001-0.1nmol g-1. Their concentrations were smaller within the K/T boundary claystone than in the sediments above and below the claystone, which are likely related to the large biomass extinction event at the end of the Cretaceous. The concentrations of 5α-cholestane and the relative ones of 17α,21β-hopane in the sediments above the boundary claystone were about a half of those in the sediments below the claystone, whereas those of 5α-ergostane, 5α-stigmastane, and oleanane in the sediments above were less than a half abundance level of those in the sediments below the claystone. Diastereomer ratios of steranes and triterpanes were nearly constant over the sediments. No tricyclic alkanes were detected in the sediments.This work was supported by the Grant-in-Aid for ScientificResearch (B) No.11440166 from the Ministry of Education, Science, Sports and Culture, Japan and the Research Grant for Fellowship No.00007064 to H. Y. from Japanese Society for the Promotion of Science
