Taphonomy of Insects from the Florissant Formation, Colorado

Jenell Jo Thoene, University of Colorado Boulder


The purpose of this study is to understand how sedimentary environments influence fossil insect preservation. Eight hundred and twenty-four fossil insects were collected from the lacustrine deposits of the Florissant Formation (Late Eocene) to study how sedimentary environments affect the completeness, quality, and orientation of fossil insects. Also examined was the level of decay and disarticulation different insect orders exhibited amongst different sedimentary environments, as well as the representation of insect diversity throughout an extensively sampled section of the Florissant Formation. Two years of intensive field collecting resulted in a collection that was under-sampled and therefore did not capture the diversity of fossil insects in the Florissant Formation. Thus, to study insect diversity within the Florissant Formation, sampling efforts must increase greatly. No significant differences were found in insect completeness, preservation quality, or orientation between the different sedimentary environments; however, there were significantly smaller specimens found in the siltstone layer. The diatom and bacterially-generated biofilm model as a mechanism for exceptional preservation is no longer supported. Finally, levels of disarticulation, decay, and the orientation varied depending on the insect order. It is recommended that actualistic taphonomic studies be conducted to further understand how insects settle through the water column.