Distributions and sources of hopanes, hopanoic acids and hopanols in Miocene to recent sediments from ODP Leg 190, Nankai Trough

The distributions and origins of hopanes, hopenes, hopanoic acids and hopanols in marine sediments from Sites 1175, 1176 and 1178, Ocean Drilling Program (ODP) Leg 190 (Nankai Trough) were investigated. The high concentrations of hopanoic acids and anhydrobacteriohopanetetrol in the sediments correspond well with a terrestrial contribution, as indicated by the abundance of higher plant-derived lipids and turbidite layers, suggesting that they are mainly transported from land. Bacteriohopanetetrol and hopanepolyols with short side chains were commonly detected down to about 400 m below sea floor. Diagenetic transformation from biohopanoids to geohopanoids can take place quickly after the death of bacteria. The presence of intact bacteriohopanetetrol in geological sediments tends to suggest an origin from in situ living bacteria, so bacteriohopanetetrol might be a potential life marker for deep sub-surface bacteria.