Quaternary events on the North Devon coast

Prof Nick Stephens's map of ket Quaternary features in the South West.  Many of the features on this map are now known to be incorrect, but note Lake Maw -- centred on the Somerset Levels, withy an overflow to the south

Been looking again at this major contribution:

Bennett, J. A., Cullingford, R. A., Gibbard, P. L., Hughes, P. D., & Murton, J. B. (2024). The Quaternary Geology of Devon. Proceedings of the Ussher Society, 15, 84-130. 

https://ussher.org.uk/wp- content/uploads/benettetal1584130v2.pdf

I think we are getting pretty close to a consensus here:

Quote:

Glaciation appears to have modified the landscape south of the Bristol Channel relatively little, although this is not surprising given that the ice from both the Irish Sea and South Wales did not penetrate far beyond the present north Devon and Somerset coast. Presumably the relatively easily deformed marine deposits flooring the Bristol Channel allowed the ice to flow along or across the valley until reaching the resistant rocks on today’s northern coast of Devon. Here, river valleys parallel to the coast and also truncated may in fact be ice- marginal landforms (Rolfe, 2015; Gibbard, et al. 2017). The BRITICE project (Clark et al., 2020) takes a broad view of the glacial limits in Britain but suggests that the pace of ice retreat from the Celtic Sea may have varied according to bed topography. In addition, Scourse et al. (2021) propose short- lived events of ice advance down the Celtic Sea that may have affected the north Devon coast and the further possibility that the ice margin had advanced as far as the shelf break at 25.5 ka.

Lake Maw is still a puzzle!  In my correspondence with Philip H and Philip G we have pondered on Lake Maw.  Use the search box to look at earlier posts.  If ice really did cross the Bristol Channel and hit up against the clifflines of N Devon and N Cornwall, in the Late Wolstonian or Late Devensian (and maybe at other times too!) then an ice barrier must have blocked the Bristol Channel and impounded a considerable meltwater lake in the Severn Estuary  -- referred to by the older workers (including Frank Mitchell and Nick Stephens) as Lake Maw.  But in that case, where are the lacustrine clays that might be expected in this lake?  

A similar lake -- Glacial Lake Teifi -- filled a broad depression in the Teifi Valley when Irish Sea ice moved in from Cardigan Bay from the W and NW.  No shorelines have been identified (which means that its surface level was anything but stable) but there are abundant laminated lake clays in many locations, as described by Fletcher and Siddle (1998) and Etienne et al (2006). At the time of its greatest extent it was more than 10 km wide and 40 km long.

doi:10.1016/j.quascirev.2005.03.019

The interesting thing about this lake is that it formed during the ADVANCE of the ice from the Cardigan bay, rather than during its dissolution.  It appears that the ice advanced over the lake deposits, creating complex structures and depositing Irish Sea till and glaciofluvial sediments as it did so,

The full sequence of events is not yet elucidated......