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Zoom Talk – Dr Stephen Davison on new Microfossils from the Stoer Group Limestones at Enard Bay
The Torridonian rocks of NW Scotland are amongst some of the oldest sedimentary units in Europe and form a significant part of the NWH Geopark. The Stoer Group is the oldest part of the Torridonian sequence and has been dated as approximately 1.2 billion years old. Most of the Stoer Group is composed of red-brown sandstones and mudstones, interpreted as being deposited by large-scale fluvial and lake systems which infilled an ancient landscape developed on the exposed Lewisian Gneiss. However, the lowermost part of the Stoer Group, which includes the type section at Stoer Bay and the rocks at Enard Bay, contains thin limestones which are not found anywhere else in the Torridonian.
The limestones have been studied for more than 50 years and have a disputed origin, having variously been interpreted as microbial stromatolites, inorganic chemical crusts, deep burial diagenetic precipitates and re-worked Palaeoproterozoic limestones. Poorly preserved organic microfossils have been recovered from the limestones and associated grey shales at Stoer Bay, but until recently, no identifiable organic remains have ever been recovered from the rocks at Enard Bay.
My talk shows some of the organic microfossils recently extracted from the limestones at Enard Bay, including examples of Lophospheridium sp. and Leiosperidia sp. which are probably the best preserved microbial remains ever recovered from the Stoer Group. These have important implications for the origin of the limestones and are amongst the oldest, possibly the oldest, microfossils ever found in the UK. The work is ongoing, with some microfossils and other possible organic structures yet to be identified.
Bio
Steve Davison is a geologist and sedimentologist currently based in North Wales. He has previously worked in research support, field archaeology and oil exploration consultancy. Previous research includes an MSc in sedimentology from University of Reading and a PhD in Quaternary glacial and glacimarine systems from the University of Edinburgh.
He has a long association with the geology of the Geopark, beginning as an HND student mapping at Enard Bay in 1987. This was subsequently followed by an MSc thesis in 1994, examining the possibility of a glacial component to the base of the Stoer Group. The current work on the limestones is partly a result of questions thrown up by the observations made as a postgraduate student 30 years ago.