PRESERVATION OF FOSSIL LEAF WAXES IN ASSOCIATION WITH THEIR SOURCE TISSUES, CLARKIA, NORTHERN IDAHO, USA

An intensive study of fossil plant tissues has been undertaken at a Mi ocene lacustrine deposit to assess the degree of preservation of the f ossil epicuticular waxes and the location of these components in the s ediment relative to the leaf fossil tissues. Comparison of the preserv ed epicuticular wax lipids with those found on modem leaf tissues indi cates that certain components have been degraded. Wax esters, aldehyde s, certain sterols, and triterpenoids were not detected, whereas, n-al kanes, n-alcohols, n-acids appear to be selectively preserved. Analysi s of different fossil leaves indicates that the distribution of preser ved epicuticular wax components differ between species. This indicates that there is an inhomogeneous distribution of plant derived lipids w ithin the sediment. However, comparison of lipid extracts from fossils of the same species shows a greater similarity within an individual s pecies, than to other species or the sediment in general. This suggest s that the gross characteristics of the original leaf wax are being pr eserved in association with fossil leaf tissues. Sampling on a submill imeter scale of sediment above and below a fossil Magnolia latahensis leaf has shown that although epicuticular lipids are found throughout the sediment, certain lipids characteristic of M. latahensis are conce ntrated at the surface of the fossil leaf. Therefore, components of th e original epicuticular waxes appear to be located at the fossil and h ave not moved into the surrounding sediment. Rapid inorganic sedimenta tion appears to effectively dilute the background lipid signature, thu s allowing the components of the preserved epicuticular wax from the f ossil leaf to be distinguished from the surrounding sedimentary lipid distribution.