Submerged forest discovery at Pendine

Dave Maynard has discovered a peat bed with tree remains at Pendine -- this is exciting, since I am not aware of any previous record of the "submerged forest" being described here.  Many thanks to him for sharing the info plus some of his observations.

He has done some splendid drone photography, and has mapped the outcrop in great detail by combining several drone images:

On the image, the peat exposures are shown in green.  They extend over a distance of c 280 m, very close to the village at the western end of the beach.

The exposures are in the vicinity of the dark-coloured rocks partly submerged by the sea in the intertidal zone, between Dolwen Point and Gilman Point.  Grid ref:  SN 23216 07770.

This exposure is very different from most of the others in West Wales, which are generally found in wide sandy bays in association with sandy beaches and storm beaches of pebbles.  Here, there is a close association with a high cliffline and abundant rockfall debris.

This is how the area looks (without all the cars) when the sandy beach is in "summertime" mode:

When Dave visited, a lot of sand had been moved out by the winter storms, and this is one of the images he obtained:

Oblique image from Dave's drone footage.  The edge of the peat bed can be seen clearly, running from approx 1 pm to 7 pm.

This is a general view showing the peat bed overlain by wave-washed and partly rounded rockfall debris, not far from the cliff face.

Dave's description:

There doesn't appear to be a record of anything on this beach, because it is only visible in fragmentary pieces and the big shows of material is west of here. Also is very noteworthy that the peat is heavily covered with rockfall from the cliff and the rapid movement of sand. The peat is low in the ground and often at the base of pools of water. No stories of blue clay underneath here! The best you will see is the peat surface pocking out through gaps in the sand.

One very strange observation is stratified deposits of sandy material forming a conglomerate, which is hard, but can be scratched away. This looks like old beach deposits formed about 4-5m inland of the peat and up against the rock debris. In places, there are large blocks that look like breccia incorporated in this sand deposit that have been broken up by wave action and tumbled around.

On the images, it looks as if there are rockfall boulders both underneath and on top of the peat layer.  Because the peat is at a low level, there are no exposures of blue clay beneath it, but this photo shows that beneath the peat bed there is a fine-grained brown silty deposit containing scattered lumps of bedrock.

 

This might be till, but it looks more like a colluvium containing local angular and sub-angular bedrock fragments.........  does it contain organic debris or roots, pollen or maybe foraminifera, or maybe even Scrobicularia fragments?  Is it a land or freshwater deposit, or something from the intertidal zone?

On some of Dave's images there appears to be a rock platform (presumably a wave-cut platform) just under the surface litter of boulders, so we can probably assume that the full sequence of deposits is less than 2 m thick.

Scattered around among the boulders and other rockfall debris there are broken chunks of "sandrock"  -  generally interpreted as cemented dune sand and often found in association with the interglacial raised beach.  (The cliffs here are made of Carboniferous Limestone, with abundant caves, but I am not sure if there are any remnants of the raised beach platform or any in situ patches of the raised beach or the cemented sands.....)  Prof David Bowen has noted that around Gilwen Point and Ragwen Point there are several exposures of cemented blocky slope breccia (head) on the cliff slopes, and also "several facies of raised beach beach shingle separated by cemented sand....." (GCR Review volume, p 83).  From looking at Dave's photos, there do appear to be three different sorts of  cemented material represented:  relatively fine-grained sandrock, presumably from old sand dunes; a cemented slope breccia full of angular fragments; and a "conglomerate" which seems to contain a greater proportion of rounded pebbles -- maybe from a remnant of the raised beach?

An exposure of cemented breccia which seems to contain some less angular material.  Could it be a cemented till?  Or even something related to the interglacial raise beach?  And does it project through the peat, or is it a detached block sitting on the surface?

So -- is there any genuine and unmodified till at this location, beneath the peat?  It may be that there is just a stony colluvium, but a small excavation might give the answer.......

The stratigraphic relationships of these assorted deposits are currently something of a mystery.    All will no doubt be revealed, in time.......

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As a matter of interest, Prof David Bowen claimed that the Pendine - Marros area was unglaciated during the Late Devensian.  On p 149 of "The Glaciations of Wales and Adjacent Areas" (2005) he published a photo of the lee side of Gilman Point, showing coarse rockfall debris / slope breccia at the base, and finer "scree" above (several facies), with a variable matrix of "finer slope wash material".

Exposure on the lee (east) side of Gilman Point -- showing very coarse limestone rockfall debris at the base, overlain by finer slope breccia (Photo: DQ Bowen)

Bowen claimed that there are no erratics in these deposits, and that the "entire exposure represents all of the last (ice age) glacial cycle."  This may be true, but we must bear in mind that there is till at Amroth and Marros, not very far away, and that on the geological map till is shown in Pendine, on Pendine Hill, and in the valley of Morfa Bychan, to the west of Gilman Point.  Is this till ancient, or Late Devensian?

Morfa Bychan Bay and Gilman Point.    The expanse of till is in the section of the 

valley closest to the camera.