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The Pleistocene History of the Birmingham District

The Pleistocene History of the Birmingham District

Birmingham, England, is built on a complex sequence of Middle Pleistocene sediments representing at least three lowland glaciations (Anglian, Wolstonian, and Devenisan). Geological mapping accounts for 75% of the landmass as Quaternary, that is, predominantly glacial-sandy till, glacial-fluvial sand, and clay and organic silt/peat. Understanding the age of Quaternary deposits related to specific glaciations is critical to establishing a geochronology of Birmingham. Professor Fred Shotton found a series of Middle Pleistocene glacial sediments, termed 'Wolstonian', intermediate in age between the Hoxnian and Ipswichian Interglacial Stages. Uncertainty surrounding the relation to East Anglian sequences implies that Birmingham sequences should be referred to as Anglian Stage. However, younger Middle Pleistocene glacial sequences occur in Birmingham (erratics dated to c.190 ka), yet there is uncertainty about the complex, inaccessible sediments, especially as deposits have similar extents with Devensian sequences.

A new regional stratigraphy of the Birmingham district shall be established, supported by Optical Stimulated Luminescence (OSL), cosmogenic exposure dating, and pollen palynology from around Birmingham to support a glacial presence during the Wolstonian Stage. The glacial stratigraphy of Birmingham is controlled to the east by the Irish Sea and North-East ice (around the sites of Wolston, Glebe Farm, Meriden Quarry, Park Farm, and Gilson) and to the west by Welsh ice (around the sites of Seisdon and Frankley). Sites establish the location of the ice through field sedimentology and mapping, and suitable samples have been processed for dating. Correlation of dating provides an important constraint on understanding the glacial history of Birmingham.

The significance of this work is correlated using stratigraphy, chronostratigraphy, and biostratigraphy, enabling complex deposits to be understood across the district. Sedimentology and geochronology on Birmingham's Quaternary deposits, deposited by extensive repeated Middle Pleistocene glaciations since the Mid-Pleistocene period, establishes that the Wolstonian Glaciation was present in Birmingham during 156-186 ka. This contributes significantly to the debate surrounding the timing of glaciations in East Anglia and across the UK. Such a finding has yet wider significance owing to the Wolstonian's relation to the equivalent Saalian Glaciation of Continental Europe while the East Anglian sequences are associated with sequences in the Netherlands, Denmark, and Germany.