Taphonomy of the insects from the Insect Bed (Bembridge Marls), late Eocene, Isle of Wight, England

Abstract

The environmental setting and taphonomy of the insect fauna of the Insect Bed, Bembridge Marls (late Eocene; 36 Ma) of the Isle of Wight is described. Cluster analysis of taxonomic data on the insect fauna of a diversity of modern tropical environments, together with that of the Bembridge Marls, shows that the insects of the latter are characteristic of a primary sub-tropical/tropical forest subject to significant seasonal rainfall. A similar approach indicates that the sample of taxa preserved in the Insect Bed is biased toward insects from leaf litter and lower herbage microhabitats. External ornamentation of the cuticle is preserved on a micron scale, and the individual microfibrils of the procuticle can be distinguished. The insects of the Bembridge Marls are remarkable in preserving cuticle and mineralized internal tissues in a largely uncompacted state. Chemical analysis (py-GC/MS) reveals that the cuticle is composed of an aliphatic polymer, possibly due to polymerization of cuticular waxes during diagenesis. No chitin was detected. The soft tissues, which include sarcolemma and muscle fibres, are preserved through replacement in calcite.