These pebbles look like rock but when you pick them up they are light and obviously organic. They are made of ancient peat that underlies the sandy beach at Whiteford Sands. The peat is about 10,000 years old and occurs in layers alternating with clay and interspersed with pebbles. These strata are being eroded away by the action of the waves. You can sometimes see the deposits outcropping during low tide at Whiteford Point – just beyond the Whiteford Lighthouse.
The pieces that break away from the seaward edge of the peat layer can be a metre or more across and these large lumps occur as islands dotted sparsely across the vast expanse of wet sand. Much smaller pieces often wash up on the strandline. The edges are rough and uneven when the peat has recently broken away. Smoother, more rounded, pieces are the result of peat fragments rolling around in the sea over a length of time. It is possible to see preserved leaves and stems incorporated into the peat. These are clues to the past environment. Apparently, no-one has yet studied in depth either these plant remains or the submerged forest timber.
Intriguingly, you can frequently find neat circular holes drilled into the peat. These boreholes have been made by boring bivalved molluscs -although they look regular enough in shape to be man-made. I have written in earlier posts about soft rock and pebbles with holes made by sea creatures. Also shells with holes made by boring bivalves. So it would seem that peat is an additional suitable substrate in which molluscs like piddocks can live equally well.
One of the pieces of peat I picked up on my last visit still had the empty shell of the mollusc in one of the borings. I don’t know whether the shells are ancient or modern. I have not seen any live molluscs in these peat colonies; or in any of the nearby colonies to be found in the clay deposits either. Only empty shells so far.
The shells are very fragile and usually break when you try to extract them. I am going to try and get some decent specimens so that I can make a definitive identification. And I will keep searching for live animals as this will show that at least some of the boreholes in the peat and clay on this Gower beach (and its neighbours like Broughton Bay) are modern. In theory, you could radio-carbon date the shells (for example, this has been done for archaeological oyster shells from Poole in Dorset) but that costs money.
Revision of a post first published 22 January 2010
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