Fig. 2.

Distribution of extractable aliphatic hydrocarbons for a representative sample. a Total ion chromatogram (TIC) for extractable aliphatic hydrocarbons for Lugovoe #13–73 m from the Redkino Horizon. The n-alkane series, pristane (Pr), phytane (Ph), and C₂₇–C₃₄ hopanes (denoted by their total carbon number and stereochemistry at C-17, C-21, and C-22, e.g., C31αβR) are labeled; ** denotes C₂₉ and C₃₀ hopenes. Note the hopane abundance dominance over other alkane compound classes. b Partial 85-Da ion chromatogram shows dominance of the n-alkane series, exhibiting a discernible odd-over-even carbon-number preference in the C₂₂–C₂₇ range, over methylalkanes