GC-MS analysis of tricyclic and tetracyclic terpanes in Proterozoic and Paleozoic sedimentary rocks

Abstract

13β(H),14α(H)-Tricyclic terpanes (TriTs) and tetracyclic terpanes, 17,21-secohopane (TetraTs), are found ubiquitously in Mesoproterozoic to Cenozoic sedimentary rocks and oils. In contrast, 13α(n-alkyl)-tricyclic terpanes (αNATTs), a series of tricyclic terpanes that have recently identified, are found only in Mesoproterozoic sedimentary rocks. Although the origins and diagenetic formation processes of these tricyclic and tetracyclic terpanes are unknown, it is hypothesized that TriTs are derived from bacteria, archaea, algae, and higher plants, while the αNATTs are derived from cyanobacteria. It also expected that TetraTs are formed by thermal maturation and biodegradation of hopanoids. In the present study, we carried out the GC-MS analysis of these terpanes found in sedimentary rocks deposited during the Mesoproterozoic era and the Devonian-Carboniferous boundary, and report chromatograms and mass spectra for C ₁₉–C ₂₆ TriTs, C ₁₉–C ₂₀ αNATTs, and C ₂₄ TetraT.