The Courtmacsherry "glacial" raised beach

  I have been looking again at the evidence for the Courtmacsherry raised beach, and am still very puzzled.  The dating of it is hugely dependent upon the reliability of OSL dating, and I'm a bit worried about some of the other grounds cited for it being formed at a time of high RSL in MIS 3 or 4.  I have nagging doubts, and remain to be convinced that it is not Ipswichian in age, like most of the other raised beaches in the SW of the British Isles.

I have been reading the excellent article by Colm O'Cofaigh et al (2012), and have concerns about the following:

Extracts from p 175

Undoubtedly there is extensive evidence for the beach along the
south coast of Ireland forming in a cold-climate environment (see
above), and indeed some of the evidence which underpins this
interpretation was first noted by Wright and Muff (1904). This
includes the presence of erratics within the raised beach gravels
and interbedding of the beach gravels with periglacial slope
breccias. Previous investigations of the sand facies that overlie the
raised beach at sites such as Howe's Strand and Broadstrand have
interpreted it as ‘blown sand’ (e.g. Synge, 1978). This is inconsistent
with the sedimentology of these sands which exhibit well defined
hummocky and swaley cross-stratification consistent with
a shallow marine rather than aeolian setting. Thus the facies
sequence of raised beach/HCS sands/SCS sands indicates
submergence following beach formation. Periglacial slope deposits
and isolated angular clasts of local bedrock within these sands
indicate the maintenance of a ‘cold’ depositional environment
during this submergence.

We suggest that high
relative sea level and the submergence indicated by the facies
sequence of raised beach deposits overlain by shallow marine sands
are related to glacioisostatic depression during ice sheet build-up on
land combined with still high eustatic sea level prior to the LGM. The
interpretation of high RSL during ice sheet build-up is consistent with
observations of erratics in the beach gravels (proposed byWright and
Muff to record deposition from floating ice) and the presence of
periglacial slope breccias interbedded with the beach and overlying
shallow marine sands.

Colm Ó Cofaigh, Matt W. Telfer, Richard M. Bailey, David J.A. Evans, 2012
Late Pleistocene chronostratigraphy and ice sheet limits, southern Ireland
Quaternary Science Reviews 44 (2012) 160-179.

First, the evidence of erratics within the raised beach gravels is NOT a ground for claiming that the beach is a cold-climate feature. Second, how do the authors know that the slope breccia is a genuine cold-climate deposit rather than one associated with rockfalls such as one sees all the time on a temperate coastline subject to wave attack?  Third, the transition from shoreline deposits to shallow-water marine deposits suggests a transgression or rising sea level, but that does not of itself prove glacio-isostasy or the advance of a glacier from the north or from anywhere else.  Raised beaches may be formed at a time of falling sea-level, or rising sea level, or indeed oscillations over a few metres over thousands of years.

The raised beach deposits are apparently devoid of organic materials -- which is a pity!  A shell fauna such as that seen in the Gower raised beaches would be rather valuable in sorting this matter out........

I'm struck by the similarity between the southern Irish sites and West Angle, at the mouth of Milford Haven.  Here there are interglacial sands, silts and clays which have been overridden and partly destroyed by advancing ice which left behind a characteristic Irish Sea till.  I have dealt with West Angle in many posts on this blog (use the search box), and I do not see any features there that might support the idea of an Early or Mid Devensian glaciation or a high RSL on the Pembrokeshire coast coinciding with a global sea-level at about - 80m.

The surveyed exposure at West Angle, showing a sequence of supposed interglacial marine and estuarine deposits overlain by till.