Chemotaxonomic classification of fossil leaves from the Miocene Clarkia lake deposit, Idaho, USA based on n-alkyl lipid distributions and principal component analyses

Fossil leaves which show excellent preservation of lipids and other organic compounds are preserved in abundance at the Miocene Clarkia lake deposit i n northwestern Idaho, USA, Eighty three fossils from nine genera which are commonly found at the site, namely Quercus, Platanus, Magnolia, Pseudafagus , Fagus, Cocculus, Taxodium, Metasequoia ann Sequoia were investigated to a ssess whether their chemical compositions can be used in chemotaxonomic com parisons. Chromatographically separated n-alkane and n-alkanol sub-fraction s were examined by GC and GC/MS to establish whether characteristic distrib utions were evident between fossils and distinct from the enclosing sedimen t. Chemotaxonomic comparisons were performed between the individual fossil specimens and six sediments using the n-alkane and n-alkanol profiles and p rincipal component analysis (PCA), Characteristic distributions were observ ed for certain genera, e.g, Platanus and Quercus, which were reproducible b etween multiple specimens of the same genus. Concentrations of the lipids i n fossils were markedly greater than in the six sediments in all of the fos sils except the conifers examined, These findings demonstrate that n-alkyl lipid distributions from fossil leaves have chemotaxonomic utility, with po tential for comparisons with modern taxa, (C) 2000 Elsevier Science Ltd. Al l rights reserved.