Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click

Thursday 1 February 2024

Cemented pre-Devensian (?) slope breccia, Traeth Mawr, Newport.

Two exposures of cemented slope deposits at Traeth Mawr, Newport.  The deposits are made of "churned" sharp-edged fragments of local mudstone, suggesting that they may have a periglacial (cold climate) origin.  There does not seem to be any sign of wave action or rounding of the fragments -- and that might suggest that at the time of emplacement sea-level was lower than it is now.  

With reference to my previous post about the Penfro Till Formation and its type localities, I think there is a Penfro Till, but it's not in the places that BGS thinks it's in. If you see what I mean.

One of the places where I think it does exist is Traeth Mawr, Newport, where on a small reef directly in front of the public car park and projecting through the sandy beach there are solidly cemented exposures of till.  Well, there's more -- and on recently exposed bits of the rocky shore platform we can see small exposures of cemented scree or slope breccia.  If my thinking is correct, there may well be a cemented suite of deposits here -- maybe to be confirmed through further observations.

I'm now certain that there is a pre-Devensian till at Black Mixen (Lydstep), Ceibwr, Witches Cauldron and Traeth Mawr -- and I think we can probably add Druidston and Whitesands to that list. At Witches Cauldron and Ceibwr there are also cemented fluvio-glacial sands and gravels.  So we are moving towards a pre-Devensian stratigraphy -- although more work is needed on this.

The west Wales deposits are of course insignificant when compared with the substantial pre-Devensian deposits found in the Midlands and Eastern England -- but it's a start.  And gradually we will begin to put right the terrible errors that stalk the pages of the GWR Wales volume published in 1989 (and, for that matter, the volume relating to SW England......).

Onwards and upwards.

No comments: