Biomarkers of Holocene buried conifer logs from Bella Coola and north Vancouver, British Columbia, Canada

The biomarker compositions of a Holocene seep oil (liquefied resin) originating from a buried log of Douglas fir (Pseudotsuga menziesii) from Bella Coola, BC, Canada, and a Holocene pine wood (Pinus sp.) sample from north Vancouver, BC, Canada, were analyzed using gas chromatography–mass spectrometry (GC–MS). The total extract of the Bella Coola sample contains the sesquiterpenoid derivative calamenene and diterpenoids of the labdane, abietane, pimarane, and phyllocladane classes. A novel series of successively degraded labdane derivatives (labdan-15-oic acid, norlabdanoic acids, drimenoic acid) was detected in the polar fraction and a diagenetic pathway is proposed. Aromatic abietanes are the major components in the neutral fraction. The neutral fraction of the pine wood contains two sesquiterpenoids (calamenene, cadalene), diterpenoids of the abietane, pimarane, isopimarane, and kaurane classes, and a series of steroids. 18-Norabieta-8,11,13-triene (dehydroabietin) is the major component among the predominantly aromatic abietanes. Based on the compositions of the terpenoids it is concluded that the diagenesis of the pine and Douglas fir logs probably occurred under anaerobic conditions leading to reductive reactions such as decarboxylation of resin acids, with concurrent oxidation reactions to form the aromatic derivatives.