Taphonomy, taxonomy and geoconservation of the ‘Upper Island Cove’ Ediacaran fossil assemblage

McKean, Christopher (2024) Taphonomy, taxonomy and geoconservation of the ‘Upper Island Cove’ Ediacaran fossil assemblage. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

three-dimensional, high relief Ediacaran fossils on the Allison Surface, Upper Island Cove, were discovered 20 years ago. This project has implemented novel methods and modern understandings of the Ediacaran biota to improve our understanding of this under-studied site. Through the collection and assessment of taphonomic and sedimentological data it can be seen that the unique preservation of the assemblage was the result of erect and reclined fronds being encased in the top centimetre of a partly lithified Td silt, prior to subsequent exhumation by obstruction scours in the lee of a later community of erect organisms. After exhumation both the upper and lower surfaces of the fronds were cast by an overlying pyritic, fine-grained Tc sandstone which led to the high relief preservation. This improved understanding of site taphonomy, alongside the addition of over 150 newly discovered specimens, led to a taxonomic reassessment of the surface and the description of three new taxa: 1) Avalofractus dosomitus sp. nov., 2) Kannabuchia artkingii gen. et sp. nov. and 3) Corellia washageuis gen. et sp. nov. New morphotypes of Arborea, Bradgatia and Charnia have also been described from the surface, including for the first-time documentation of a differentiated upper surface in Bradgatia. The presence of unique taphonomic processes and endemic species on the Allison Surface highlight the importance of protecting the site. As such a novel approach to site observation was implemented at the surface, which shows that the fossils are at risk to both anthropic and environmental factors. The mitigation techniques that have been suggested to protect the site from irreparable damage can also be applied to other at-risk localities worldwide.

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