Comparison of Leaf Lipids from a Fossil Ginkgoale and Its Modern Counterpart at Two Degradation Stages

Abstract

The investigation of fossil flora by organic geochemical methods has been widely used for the last decade and numerous studies established the precise chemical composition of lipids from fossil plants (e.g. Logan and Eglinton, 1994). Such studies provided a better understanding of the origin of organic matter in various sediments (e.g. Rieley et al., 1991). While several studies investigated early and late diagenesis of sedimentary lipids (e.g. Cranwell 1981), little is known about diagenesis of lipids in fossil leaves themselves. In the present study, we examined the effects of diagenesis on leaf lipids, by investigating the chemical composition of total leaf waxes from a fossil plant, and from its modem equivalent at two different degradation stages. The fossil plant studied is the Ginkgoale Eretmophyllum andegavense, was collected in an exceptionally well preserved fossil flora occurring in the 'Argiles du Baugeois', a Cenomanian lagoonal Member located near Angers, France (Pons et al., 1981). Waxes from fresh leaves and leaves from a litter of the only extant Ginkgoale, Ginkgo biloba, were analysed along with leaf waxes from E. andegavense in order to: (i) establish a stability scale for the leaf lipids of G. biloba, (ii) test this stability scale on E. andegavense, and (iii) reveal possible common compounds of taxonomic value between both extant and fossil Ginkgoale.