USING EXPERIMENTAL TAPHONOMY TO EXAMINE THE ROLE OF SEDIMENTS ON BIOFILM FORMATION ON HARD AND SOFT TISSUES

Exceptionally preserved fossils have both skeletal and soft tissues, are found most frequently in Konservat-Lagerstätten deposits, and reveal information about past body plans and ecosystems that would not normally be included in the geologic record. The mechanisms of preservation of these tissues involve several factors including, but not limited to: rapid isolation under reducing conditions, which prevents scavenging and delays decay, and rapid mineralization of the tissues often driven by microbial processes. Taphonomy experiments test the role of each factor in the early mineralization of soft tissues. Experiments performed by previous researchers have determined that microbes, particularly biofilms, play a vital role in the early mineralization of soft tissues. These experiments provide a model for biofilm-mediated fossilization of tissues in Konservat-Lagerstätten.

Most taphonomy experiments exclude sediments to simplify observations of developing biofilms. The sediments introduce other conditions that complicate interpretations of the results. Many obrution Konservat-Lagerstätten have fine-grained sediments encasing fossils, yet the role of the sediments in the formation of biofilms and the subsequent preservation of the tissues has only rarely been tested.

Taphonomy experiments involving the burial of Biomphalaria glabrata in fine-grained sediments and artificial seawater sampled at 1, 2 and 8 weeks demonstrate that sediments affect biofilm development. Extensive biofilms were not observed on the exoskeletons until 8 and were never observed on any of the soft tissues. Hard sediment plugs formed in the opening of several of the snail shells, isolating the soft tissues and better preserving the soft tissue morphology than those without sediment plugs. These initial results highlight the importance of sediments in the fossilization process because of their influence on biofilm development.