Abstracts Session 3
Professor Paul Wignall
Professor of Palaeoenvironments
University of Leeds
The end-Triassic mass extinction: the view from eastern England
Professor of Palaeoenvironments
University of Leeds
The end-Triassic mass extinction: the view from eastern England
The end-Triassic mass extinction, a little over 200 million years ago, is one of the “big 5” crises of the fossil record. Victims include many groups of molluscs, such as the bivalves and ammonites, and on land many groups disappeared, paving the way for a world dominated by dinosaurs. Like all extinction crises, the end-Triassic one coincides with the eruption of gigantic volumes of lava from a mantle plume, with the gases released being widely held to be responsible for devasting climatic consequences. In this case the volcanism was centred to the south west of the British Isles in the centre of the Pangea supercontinent and we know it as the Central Atlantic Magmatic Province.
All of these events are recorded in the British Isles in the Penarth Group: a fascinating succession of rocks that record the transition from the desert conditions of the latest Triassic to marine flooding and offshore deposition in the earliest Jurassic. It is within this succession of rapidly changing environmental conditions that the mass extinction is recorded. In eastern England, the first phase of the mass extinction coincides with a change from marine siltstones to curious pale mudstones that probably formed in non-marine conditions, whilst the a second phase coincides with the onset of anoxic deposition. How these changes relate to the regional history of the mass extinction will be discussed in the talk.
All of these events are recorded in the British Isles in the Penarth Group: a fascinating succession of rocks that record the transition from the desert conditions of the latest Triassic to marine flooding and offshore deposition in the earliest Jurassic. It is within this succession of rapidly changing environmental conditions that the mass extinction is recorded. In eastern England, the first phase of the mass extinction coincides with a change from marine siltstones to curious pale mudstones that probably formed in non-marine conditions, whilst the a second phase coincides with the onset of anoxic deposition. How these changes relate to the regional history of the mass extinction will be discussed in the talk.
Professor David Bridgland
Professor of Physical Geography
Durham University
Quaternary evolution of the Trent: Knowns and Unknowns about its complex drainage evolution
Britain’s third river, the Trent, straddles the boundary between the area glaciated and unglaciated during the Late Pleistocene, although much of its catchment is inherited from a system entirely obliterated by our most extensive glaciation nearly half a million years ago: the ‘Anglian’. A geo-archaeological project has firmed up our understanding of the complex evolution of drainage hereabouts, with glacial effects strangely bringing about repeated northward diversion within Lincolnshire. The first diversion coincided with the obliteration of the pre-Trent system, named ‘Bytham’ (after Castle Bytham), which had drained from the West Midlands across East Anglia. The first Trent emerged from beneath the Anglian ice, reusing parts of the Bytham system, and was essentially a Soar–Derwent. We know little about any upper catchment in the West Midlands and are uncertain about its lower course, although it probably used the Lincoln (Witham) Gap. It seems that the Middle Trent alignment was first established by a later, poorly understood glaciation around 250,000 years ago. The location of Lincoln was on the Trent course until the very end of the Pleistocene, when deglaciation and drainage of the ice-dammed ‘Lake Humber’ resulted in the modern Trent course via Gainsborough to join the Yorkshire Ouse.
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