The chemical structure of Gloeocapsomorpha prisca microfossils: Implications for their origin

Two Estonian Kukersites (Ordovician) and two sampler from the Guttenberg Me mber (Ordovician) of the Decorah formation (North America) containing botry oidal aggregates of Gloeocapsomorpha prisca were investigated by RuO4 chemi cal degradation, FTIR, and flash pyrolysis-GC/MS to obtain information abou t the polymeric structure of these microfossils. The products formed upon o xidation by RuO4 were analysed by GC/MS and revealed the presence of a wide range of carboxyl and/or carbonyl moiety containing compounds with carbon skeletons ranging from C-5 to C-20. The Estonian Kukersites reveal the pres ence of a characteristic set of mono-, di-, and tricarboxylic acids. These compounds suggest that the Estonian Kukersites are composed of a polymer co nsisting of mainly C-21 and C-23 n-alkenyl resorcinol building blocks. Simi larly, although the tricarboxylic acids are not present, the RuO4 degradati on product mixtures of the Guttenberg Member samples, suggest a poly(n-alky l resorcinol) structure. The higher thermal maturity is most likely respons ible for the different chemistry and morphology of the G. prisca microfossi ls in these samples. Because compounds like n-alkenyl resorcinols are known to polymerise under oxygenated conditions even in an aqueous environment. it is nut per se necessary that these microfossils are composed of a select ively preserved biopolymeric cell wall. It is also possible that G. prisca microfossils are composed of a cell wall or sheath component that polymeris ed during senescence or diagenesis of the organism. Copyright (C) 2001 Else vier Science Ltd.