The Whitesands boulder bed (Whitesands 1)

I have to admit to being somewhat mystified.  I went over to have a look at Whitesands, near St David's, the other day -- in the rain, which made scrambling about and observing rather difficult.  The Quaternary exposures have changed a great deal over 50 years, and one thing which is now very prominent is the boulder bed which rests on an undulating and very smooth bedrock surface just above HWM.

There is nothing like this anywhere else in West Wales, which explains why I'm mystified........

As we can see above, the boulders are typical glacial erratics, mostly igneous and mostly from the PreCambrian and Ordovician igneous rock outcrops os the area around St David's Head. Some of them are more than 2m long, and must weigh in the region of five tonnes.  Some are more rounded than we might expect of "normal" glacial erratics, and some have quite pronounced weathering crusts -- suggestive of great age.    They do not appear to have fallen out of the retreating cliff of Pleistocene sediments, although there are some boulders still embedded in the slope breccia.   The boulder bed occupies the same position as the raised beach elsewhere  -- ie resting directly on the rock platform which we must assume is the product of interglacial coastal processes at a time of higher sea level.  So are the boulders the last traces of an ancient (Anglian?) glacial episode, left stranded when the finer materials were dispersed by wave action?  There are some clues, as we see in these photos:

I would like to say that there is a raised beach here, but  sadly there isn't.  At least, nothing is currently exposed.   But what we do see is a layer about 1m thick resting on the rock platform and solidly cemented by reddish iron oxide and black manganese oxide cement. Some boulders are embedded in this material, in a matrix made mostly of angular or brecciated slope deposits.  I think some boulders remained trapped since the last interglacial, and others have been extracted by later slope processes or -- more likely -- by overriding ice during the last glaciation.

Fifty years ago I proposed that the weathered boulders visible in the cliff face slope deposits were derived from ancient glacial deposits -- and on balance I still think that.  The Devensian glacial deposits are higher in the sequence, as I will describe in another post........

All in all, a rather intriguing site.

PS.  These exposures are seen in the low cliff face to the south of the Whitesands car park.  They are quite difficult to tie in with the exposures to the north of the car park.