The Fidelity of Fossil Assemblages

1. An Exercise at Recognizing Good vs. Poor Spatial and Temporal Fidelity The Fidelity of Fossil Assemblages

2. Assemblage Types • Biocoenosis: All members of the community are represented. • Thanatocoenosis: All fossils present were members of the community, but some members are missing. • Taphocoenosis: Some fossils present were not members of the community – time averaged (poor temporal fidelity) or transported (poor spatial fidelity) assemblage

3. How Do You Distinguish Among Assemblage Types? • Each should have some predictable set of biostratinomic features. • Each should have different bioclast fabrics. • Each should have different sedimentologic characteristics.

4. Problem: Case of Unusual Preservation • Find a strangely preserved fossil assemblage in Hamilton Group rocks (Middle Devonian, 350 Ma) from western New York State. • Found in thin limestone beds. • A large interior seaway sat on the interior of North America at this time. • Your task: Determine which type of assemblage is represented. • The following slides and associated notes will guide you through the problem.

7. c a b

10. C A B

13. c A b a B C d

15. A