Investigating the impacts of transport and decay on the polychaete alitta virens: : implications for the taphonomy of the Burgess Shale
Student thesis: Doctoral Thesis
Interpreting how far organisms within fossil assemblages may have been transported and if they all originated from the same location, is fundamental to understanding whether they represent true palaeocommunities. The Burgess Shale of British Columbia is the archetypal fossil Konservat Lagerstätte, preserving soft-bodied organisms from the Middle Cambrian (505 Ma). These fossils have been fundamental for understanding the origin of all major animal groups on Earth during the Cambrian explosion; and more recently, have been used to investigate the evolution of community structure through time. This thesis aims to expand our understanding of the transport of soft bodied organisms, potential biases introduced through transport processes, and ultimately to test the competing hypotheses for the Burgess Shale biota, on the extent of transport the animals, of the Burgess Shale underwent before ultimate burial. This aim was achieved by (i) conducting novel, systematic taphonomic experiments with the soft-bodied organism, Alitta virens in an annular flume. This allowed for accurate replication of a range of laminar to turbulent sediment-laden flow types; (ii) compiling indices of degradation from transport and decay that enabled quantification and comparison of the degree of degradation across experiments and within Burgess Shale fossil material; and (iii) testing the survivorship potential and biological capabilities of Alitta virens after transport. Experimental work showed that (i) recently deceased polychaetes were capable of remaining intact over long distances in a range of flow types with little damage; (ii) Alitta virens can be transported by similar flows identified in the deposits of the Burgess Shale for tens of kilometres without additional damage beyond that already experienced due to pre-transport decay; and (iii) Alitta virens can survive transport and regain biological capabilities after transport in oxygen deficient environments. These results highlight the effects from transport induced biases on soft-bodied organisms and how these biases may have important implications for the palaeocommunity fidelity of Lagerstätten entombed within density-flow deposits.
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