An unusual preservation of fossil plants from cumbria: Diagenetic and environmental significance

Lower Carboniferous fossil plants preserved as uncompressed external casts of calcite are recorded and described from a micritic limestone found in Cumbria. Most can be identified as the small leafy twigs of Archaeosigillaria kidstoni Kräusel and Weyland, but others are unidentified plant axes. Sporangia are recognised for the first time in Archaeosigillaria. Reasons for the unusual mode of preservation are considered. Rapid lithification of sediment is indicated by an erosional surface at the top of the plant bed and the presence of clasts of the latter in the overlying limestone. Subsequent plant decay probably left voids which became filled by acicular carbonate cement later altered to radiaxial fibrous calcite. The occurrence of inferred evaporite pseudomorphs in associated nodules suggests a highly saline environment which may have contributed to the lack of plant decomposition before burial.