The "sterile blue clay" and possible glacial deposits at Westward Ho

Peat beds underlain by stony blue clay at Westward Ho.  Looks familiar.........

At Westward Ho there is a Pleistocene sequence resting on a spectacular raised beach on the shoreline, and also a "Holocene sequence" exposed occasionally on the foreshore.

There are lots of records of a "sterile blue clay" underneath a Mesolithic midden and a peat bed and submerged forest layer on the foreshore.  According to Prof Nick Stephens in the 1970 "Glaciations of Wales" volume (p 285) the clay grades up to an upper clay layer containing pollen and other organic remains, and beneath it there is a blocky breccia presumably derived from bedrock outcrops. Balaam et al, writing in 1987, referred to the underlying material as "drift" -- and that term has of course always been used for materials of glacial origin.   Stephens also suggests that the clay is underlain in places by beach cobbles and boulders, and that where a surface is visible there are signs of a "rough polygonal pattern" indicative of a permafrost environment.

It's more than a little confusing, but there are obvious similarities with Amroth, Marros, Freshwater West and other sites on the south Pembrokeshire coast where exposures of the submerged forest are occasionally exposed.

Here we find a list of publications that mention the blue clay:

 https://www.heritagegateway.org.uk/gateway/Results_Single.aspx?uid=MDV44568&resourceID=104

There is also a section by Stewart Campbell in the GCR volume for South-West England -- on p 224.

So could the sterile blue clay be a till deposited on the shoreline by glacial ice coming from the west or the north?  More investigations are clearly needed......

But there is another interesting comment in Prof Stephens's book chapter, where he refers to an "upper head" deposit in cliff sections at Westward Ho which contains "some pebbles derived from a till" which he sees as a probably the equivalent of the Fremington till found just a few miles away.  He describes no coherent till, but the occurrence of the erratics in a distinct slope breccia layer above the "lower head" suggests a close similarity with Abermawr and many other Pembrokeshire coastal locations where a coherent till layer is present in the same stratigraphic position.  Stratigraphy, in general, does not lie -- and we need to consider the possibility that there might be a late Devensian (or maybe older) till somewhere in the vicinity, redeposited or rearranged as at Ragwen Point (see my recent post).

On the Westward Ho cobble ridge:

https://studylib.net/doc/8383073/westward-ho--cobble-ridge

The origin of the ridge is not known, although Keene (1996) regards it as a comparatively recent feature. Hall (1879) described a peat and blue clay deposit about 400 m seawards of the cobble ridge and Rogers (1908) recorded remnants of former forest, a kitchen midden and a submerged pebble ridge in the intertidal area. The peat contained leaves, seeds and fruits ofiris, oak Quercus, hazel Corylus, alder Alnus, elder Sambucus, sea aster Aster tripolium,common orache Atriplex patula, blackberry Rubus, dogwood Cornus and lesser spearwort Ranunculus flammula. Shells of oyster Ostrea and limpets Patella were also recorded. The blue clays were reported to include flint flakes (thought to be Neolithic in age), small pebbles and angular fragments of Carboniferous rocks. The mud-snail Hydrobia ulvae was common and bones were said to include red deer Cervus elephas, and Celtic shorthorn cattle Bos longifrons. Since most of the sediment disappeared before modern interpretation and dating techniques were available, the records have to be taken as a possible indication that the cobble ridge lay seawards of the position of the submerged forest and that the land behind it was well colonized by vegetation. The similarity with the development of the cobble ridges at Clarach and Ynyslas on the Welsh coast (see Figure 8.15) may indicate a much earlier age (about 4000 years BP) for Westward Ho!. In contrast to summer depths of sand on the western beach of up to 1.2 m, erosion during the winter of 1983–1984 exposed a thick band of head, suggesting that a wide apron of periglacial debris may have extended some distance seawards of the present-day shoreline (Keene, 1996) and this may provide an alternative explanation for the location of the submerged forest. Erosion of such deposits would provide the source for a transgressing postglacial beach. Samples from the top of the peat bed were radiocarbon dated to 6585 ± 120year BP (Q-672; Churchill and Wymer, 1985) and 4995 ± 105 years BP (Kidson, 1977). The Holocene sequence is described in detail by Campbell (1998) following description of inner and outer peats by Balaam et al. (1987) which indicates that the outer peat was inundated by marine/estuarine conditions about 5200 years BP.

Extracted from the Geological Conservation Review

You can view an introduction to this volume at http://www.jncc.gov.uk/page-2731© JNCC 1980–2007 Volume 28: Coastal Geomorphology of Great Britain 

Chapter 6: Gravel and ‘shingle' beaches – GCR site reportsSite: WESTWARD HO! COBBLE RIDGE (GCR ID: 2110)3

More work is needed here........