Abermawr on the north Pembrokeshire coast is one of the most interesting -- and important -- Pleistocene sites in Wales, spanning a full glacial cycle. I described the sequence in detail in my doctorate thesis of 1965, and that description and interpretation has found its way into many subsequent publications. However, it is now a bit misleading, since the cliff exposure has changed in several important respects over the last 50 or 60 years. That's because the cliff has retreated in places by as much as 30m, exposing a broken ancient cliffline, part of which is shown in the photo above. We can see the fine-grained Irish Sea till at the top of the photo, but beneath it the blocky slope breccia is chaotic, non-stratified and virtually homogenous. Just one "stratigraphic unit". Now look below.
In 1960-65 there was an exposure of what I referred to as "flaky gravels" which contained less blocky material than the layers above and below it, but I always assumed that this was one of four "periglacial facies" within the Main Head horizon, perhaps accumulated under less severe permafrost conditions. Shall we say that DQ Bowen was perhaps in too much of a hurry when he recorded what he thought was the sequence of deposits at Abermawr? Let's hope this inaccuracy has not caused too much confusion among generations of field trip students. At least the sequence is right in the QRA booklet of "classic Quaternary sites":
In the QRA Field Guide (2001) Kenneth Rijksdijk and Danny McCarroll referred to just one horizon beneath the Irish Sea till, which they described as a "locally derived breccia unit". That is what can be seen today -- the section has changed a great deal since 1960.
Another photo (taken today) of the breccia beneath the Irish Sea till. I now think that some of the variations in texture are related to the nature of the buried rock cliff that was being broken down, including lithology (which is quite variable hereabouts), structure and surface characteristics.