Figure 2.

Chromatograms show detector response (FID counts) versus time for Nachukui Formation samples. (a) n-alkanoic acids from sample KU107 with typical even-over-odd preference for HMW plant waxes (C₂₆–C₃₄) that are highlighted in (b). (c) n-alkanes from the same sample, KU107, with and odd-over-even preference in the HMW n-alkanes (C₂₇–C₃₅). Many n-alkane samples had an unresolved complex mixture (UCM) that eluted in the early part of the chromatogram but did not interfere with carbon isotope analysis. Panel (d) illustrates the n-alkanoic acids from KU114 where homologous series of exogenous HMW compounds not found in plant waxes were also present. The exogenous compounds are highlighted in panel (e). These include (ω – 1) keto-, (α,ω) di- acids and hydroxy acids identified from interpretation of mass spectra [47] indicative of additional (e.g. microbial) sources of alkanoic acids or degradation products of plant n-alkanoic acids. Carbon isotope ratios of plant waxes were measured in sample KU107, but not in KU114. The asterisk represents the internal standard.