Biomolecular Preservation of Miocene Fossil Liquidambar from Tiantai, China and Clarkia, USA: Implications for Palaeoenvironmental Study

Biomolecular characteristics of fossil Liquidambar from the Miocene Shengxian Formation, Tiantai, Zhejiang province in eastern China and Miocene Clarkia sediment, Idaho, U.S.A., are obtained by means of Pyrolysis-Gas chromatography-Mass spectrometry analysis (Py-GC-MS). Their modern equivalent (Liquidambar formosana) collected from Nanjing, eastern China, is also analyzed for comparison. The total ion chromatograms (TIC) of modern L. formosana leaves shows abundant pyrolysates of lignin, polysaccharide, aliphatic acid, and amino acid. However, only one polysaccharide molecule, i.e., levoglucosan, is retained in fossil Liquidambar leaves from the two Miocene sites with the Tiantai specimen possessing higher intensity. As expected, some lignin pyrolysates including benzene, phenol, guaiacol, vinylphenol and their derivatives, are detected in Miocene Tiantai L. miosinica. However, the lignin components with large molecular weight other than benzene and phenol compounds, are absent in Miocene Clarkia L. pachyphyllum. Abundant pristene and homologous series of n-alk-1-ene/n-alkane pairs with a long retention time are shown in pyrograms of both Tiantai and Clarkia fossils. Based upon our Py-GC-MS data, the molecular preservation in these Liquidambar leaf samples can be ranked as the following (from high to low quality respectively): modern sample >Tiantai sample >Clarkia sample. Vinyl phenol, an important compound, is present in modern and Tiantai Liquidambar leaves, while absent in Clarkia sample, implying that vinyl phenol may be sourced from lignin for Liquidambar leaves. Our data support the hypothesis of in situ polymerization for the origin of long-chain homologous series of n-alk-1-ene/n-alkane pairs as leaf alteration products. Our data have implications of the impact of leaf degradation toward biases for palaeoenvironmental reconstruction using stable carbon isotope of fossil plants, and suggest the importance of evaluating molecular preservation of fossil leaf tissues prior to the application of carbon isotope compositions of fossil leaves.     

Raman spectroscopic detection of key biomarkers of cyanobacteria and lichen symbiosis in extreme Antarctic habitats: Evaluation for Mars Lander missions

With proposals that micro-miniaturised Raman spectrometers could soon be part of a suite of analytical instrumentation on the surface of Mars, it is critically important to examine the spectral information that could be forthcoming from attempts to determine key molecular biosignatures under the hostile conditions of extra-terrestrial planetary exploration. Current approaches include the analysis of genuine martian geological material in the form of the SNC class meteorites, the formulation of simulated martian regoliths and the examination of putative martian terrestrial analogues; the latter provide the basis of this paper in the form of Antarctic extremophile habitats. In particular, specimens of epilithic, chasmolithic and endolithic lichen and cyanobacterial colonies sampled along a progressively worsening transect towards a “limits of life” situation, beyond which survival of organisms becomes impossible, provide what is arguably the best terrestrial proving-ground for prototype Raman spectrometers for martian exploration. Here, we report the results of experiments on these extant Antarctic extremophile colonies using a range of Raman excitation wavelengths and experimental conditions and also include a compilation of molecular spectral biosignatures, which may be considered as a suitable database for recognition of bioorganic modification of geological strata.