What we used to call the "Upton Warren Interstadial" now appears much more complex......
http://earthwise.bgs.ac.uk/index.php?title=Onshore_stratigraphical_record,_Quaternary,_Cainozoic_of_north-east_Scotland&action=edit
Middle Devensian (OIS 3)
Periglacial and glacial environments prevailed across much of continental north-west Europe during OIS 3 and glaciers probably existed in the western Highlands for most of the time. There were relatively warm periods between 50 to 41 ka and 37 to 36 ka on the Continent (Huijzer and Vandenberghe, 1998), the former being correlated with the Upton Warren Interglacial of the British chronostratigraphy (P915253; P915254). There is also evidence of two interstadials at roughly equivalent times in the Scandinavian record (P915290). The younger of the two, the ‘Sourlie Interstadial’ is apparently represented by organic deposits beneath till in the lowlands around Glasgow, where reindeer, woolly rhinoceros and mammoth roamed in a tundra-like environment (Jardine et al., 1988; Sutherland and Gordon, 1993). Reindeer bones found in caves near Inchnadamph, Ross-shire, also date from the Middle Devensian (Lawson, 1984). However, there are no known representative organic deposits in north-east Scotland, although the district was probably free of ice. The Crossbrae Peat (Site 5) was originally thought to date from between 22 and 26.5 ka BP, but it is now correlated with OIS 5a or 5c (Whittington et al., 1998).
Sand within the glaciofluvial Byth Gravel at the Howe of Bythe Quarry (Site 6) has yielded luminescence ages of about 45 and about 37 ka, implying the presence of glacier ice in the vicinity (Hall et al., 1995b). This Middle Devensian glaciation would correlate with the Skjonghelleren glaciation of Norway (P915290), when ice probably crossed the North Sea basin (Carr, 1998; Sejrup et al., 2000).
Amino-acid ratios and radiocarbon dates on shells within rafts and tills in the Whitehills Glacigenic Formation suggest that the deposits are derived from cold-water marine muds of Middle Devensian age. More specifically, the ratios correlate with the Bö Interstadial of Norway (P915290), for which ages from 40 to 80 ka have been proposed by Miller et al. (1983) and the higher estimates are favoured by Sejrup et al. (2000). The rafts of the Clava Shelly Clay near Inverness are also thought to have been originally deposited during that interstadial (Merritt, 1992b). Oddly, there appear to be nocorrelatives of the younger Ålesund Interstadial of the Norwegian sequence in north-east Scotland (Peacock and Merritt, 1997).
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On the matter of Mid Devensian sea-levels, this is a figure I have published before:
It shows that in the Mid Devensian there was still so much ice on land globally that sea-level was well depressed -- the figure for the interstadial period around 40,000 years ago seems to be c -60m to -40m. That gives us water in St Gerge;s Channel -- but the floor of Cardigan Bay might have been dry (or probably soggy) land. But we still do not know how much isostatic depression there might have been; and we do not know how much Late Devensian glacial and fluvioglacial sediment has accumulated and contributed to the shallowing of the Mid Devensian sea floor.
Periglacial and glacial environments prevailed across much of continental north-west Europe during OIS 3 and glaciers probably existed in the western Highlands for most of the time. There were relatively warm periods between 50 to 41 ka and 37 to 36 ka on the Continent (Huijzer and Vandenberghe, 1998), the former being correlated with the Upton Warren Interglacial of the British chronostratigraphy (P915253; P915254). There is also evidence of two interstadials at roughly equivalent times in the Scandinavian record (P915290). The younger of the two, the ‘Sourlie Interstadial’ is apparently represented by organic deposits beneath till in the lowlands around Glasgow, where reindeer, woolly rhinoceros and mammoth roamed in a tundra-like environment (Jardine et al., 1988; Sutherland and Gordon, 1993). Reindeer bones found in caves near Inchnadamph, Ross-shire, also date from the Middle Devensian (Lawson, 1984). However, there are no known representative organic deposits in north-east Scotland, although the district was probably free of ice. The Crossbrae Peat (Site 5) was originally thought to date from between 22 and 26.5 ka BP, but it is now correlated with OIS 5a or 5c (Whittington et al., 1998).
Sand within the glaciofluvial Byth Gravel at the Howe of Bythe Quarry (Site 6) has yielded luminescence ages of about 45 and about 37 ka, implying the presence of glacier ice in the vicinity (Hall et al., 1995b). This Middle Devensian glaciation would correlate with the Skjonghelleren glaciation of Norway (P915290), when ice probably crossed the North Sea basin (Carr, 1998; Sejrup et al., 2000).
Amino-acid ratios and radiocarbon dates on shells within rafts and tills in the Whitehills Glacigenic Formation suggest that the deposits are derived from cold-water marine muds of Middle Devensian age. More specifically, the ratios correlate with the Bö Interstadial of Norway (P915290), for which ages from 40 to 80 ka have been proposed by Miller et al. (1983) and the higher estimates are favoured by Sejrup et al. (2000). The rafts of the Clava Shelly Clay near Inverness are also thought to have been originally deposited during that interstadial (Merritt, 1992b). Oddly, there appear to be nocorrelatives of the younger Ålesund Interstadial of the Norwegian sequence in north-east Scotland (Peacock and Merritt, 1997).
=========================
On the matter of Mid Devensian sea-levels, this is a figure I have published before:
It shows that in the Mid Devensian there was still so much ice on land globally that sea-level was well depressed -- the figure for the interstadial period around 40,000 years ago seems to be c -60m to -40m. That gives us water in St Gerge;s Channel -- but the floor of Cardigan Bay might have been dry (or probably soggy) land. But we still do not know how much isostatic depression there might have been; and we do not know how much Late Devensian glacial and fluvioglacial sediment has accumulated and contributed to the shallowing of the Mid Devensian sea floor.
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