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Proceedings 19
Worsley, P. (2024). Some aspects of the glacial geology of the Shrewsbury area. p.1-6.
The Late Devensian glacial history of the Shrewsbury area concerns the relative extents of two independent ice sheets respectively sourced from the Irish Sea and central Wales. The former, moving south, arrived first; the latter expanded from the west. A former quarry at Mousecroft Lane in southwestern Shrewsbury exposed till and glaciofluvial sediments of the Irish Sea ice (Stockport Formation) unconformably overlain by Welsh glacigenic sediments consisting of a palaeosandur of sand and gravels capped by a till (Shrewsbury Formation). The Stockport Formation deposits are associated with a complex ice-contact environment and burial of detached ice blocks. Some of these blocks survived until after the withdrawal of the Welsh ice and created numerous kettle holes in the Shrewsbury district. The infill of one of these at Condover contained the remains of several mammoths of Late Glacial age. The meltwaters derived from the Irish Sea glacier deglaciation created a new outlet for the River Severn at Ironbridge and a series of glacial lakes ensued as the new river course progressively incised to a lower bedrock threshold.
Worsley, P. (2024). On the significance of a glacially-derived Lower Jurassic ammonite fragment from Vennington, west Shropshire. p.7-13.
The re-discovery of a fragment of a Lower Jurassic ammonite close to the Welsh border in western Shropshire supports the hypothesis that an incursion of the Irish Sea Glacier during the Last Glaciation Maximum (LGM) extended further westwards than hitherto understood. The most likely source of the ammonite is the Lower Jurassic Prees outlier which crops out some 40 km to the north east. Liassic fossils eroded by the Irish Sea glacier and later incorporated within its sediments in south Shropshire have been reported since 1864 and are to be expected in the area which it covered.
Worsley, P. (2024). A glacially striated dolerite outcrop in the bank of the River Severn near Crewgreen, Montgomeryshire. p.14-18.
A rare example of a lowland glacially striated and smoothed dolerite bedrock outcrop has been rediscovered in the alluvial banks of the River Severn just inside the Welsh border next to Shropshire. It reveals a clear west to east palaeoglacier flow direction. This trend is conformable with the ice-smoothed surfaces and feint striae lying 3 km to the south west on the summit of the Breidden Hills at Rodney’s Pillar, 300 m above the modern Severn floodplain. These two locations suggest an ice thickness significantly exceeding 300 m some 20 km from the Welsh readvance glacial limit during the Devensian Last Glacial Maximum in eastern Shrewsbury c. 20 ka BP.
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Worsley, P. (2024). Some aspects of the glacial geology of the Shrewsbury area. Proceedings of the Shropshire Geological Society, 19, 1-6. ISSN 1750-855X (Print), ISSN 1750-8568 (Online) [Online at www.shropshiregeology.org.uk/Proceedings; printed copy in press]
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