Newgale Submerged Forest - 2014 exposures

 

Been over to Newgale today, to inspect the exposures of the submerged forest.  Very interesting.  It was raining and blowing, but at least I managed to get some photos......

The top three photos are of the peat beds which are normally covered by sand -- the beach is now about 2m lower than it was, following the winter storms.  As we can see, some of the peat bed exposures are coherent, and other sections are being broken up into rills by water streaming up and down the beach.  Most of the pebbles you can see around these rills have been dragged down from the storm beach and dumped here to replace sediments that have been destroyed. 

The lower two photos show some of the woodland remains.  The exposures here are very different from those at Ynyslas, where actual tree stumps are exposed at the moment -- here we just get occasional traces of root systems, and a lot of debris embedded in the peat.  There are wood fragments everywhere, especially on the southern part of the beach, near the southern cafe and caravan park.  The biggest piece of wood which I found was a long tree trunk about 6m long; and the thickest was about 1m across.  So we are talking about a woodland of quite mature trees.

The stratigraphy is much more complex than I had imagined.  I hope some bright young thing from one of the universities has been looking at it, and making an accurate record......

In Newport the peat bed and submerged forest lies directly on till and frost-shattered (periglacial) debris -- but here, in a much more open environment, the peat bed is quite thin -- mostly less than 50cms thick -- and is resting on a variety of different materials -- sandy gravelly material in some places and actually on beach pebbles in other places.  These beach pebbles are loose and unconsolidated, but in a few places there are exposures of solidly concreted beach and river gravels which may even be interglacial in age.  All very complicated.....

 The peat beds in this area are quite thin, and are underlain by sandy and gravelly 

unconsolidated material.

Here the peat bed is also thin -- just a few cm thick -- and is underlain by unconsolidated storm beach material.  Was this material thrown over an advancing storm beach ridge into the boggy area beyond the ridge, in exactly the same fashion as we have seen in recent weeks when the storm beach advanced across the road?

A patch of solidly cemented beach or river gravel exposed through the sand.  One cannot see the precise stratigraphic relationship with the peat beds.   Is this material the same age as the cemented interglacial raised beaches that we see in other parts of Pembrokeshire?

Another much larger exposure of this cemented beach - river gravel material, standing up as a pedestal.

In trying to work out what has happened here, my best bet is as follows.  There are some very old deposits here -- maybe dating from the last interglacial.  These materials must have been overridden during the Devensian ice advance of the Irish Sea Glacier, but we see no signs of till or periglacial materials out here in the open bay.  Peat beds and woodland then started to form after the ice retreat, when the coastline was far out to the west. So some peat beds might be more than 7,000 years old.  I think these peat beds and the forest might have survived for at least 5,000 years -- this could be established by pollen analysis and examination of the tree species represented.  The sea rose inexorably, and as it did so it drove a storm beach ridge eastwards, covering the old peaty / woodland area bit by bit, leaving it submerged beneath pebbles and sand.  Within the last 2,000 years or so the eastwards advance of the storm beach ridge has slowed down as sea level has stabilised, but we know that it has continued because historical records show that there have been at least two other inns at Newgale, each of them in the area now submerged beneath the beach.  The current Duke of Edinburgh Inn, alongside the road that has been blocked by pebbles several times this winter, is equally vulnerable -- and one wonders how long it will survive!

The interbedding of storm beach pebbles and peat beds suggests to me individual storm events in which waves have overtopped the ridge, flinging pebbles onto the peaty boggy area on the landward side -- then followed by more peat formation, when "normal" waterlogged or lagoonal conditions returned.

So it is quite possible that the peat beds are of all sorts of ages, with some of them shown in the photos above no older than a few centuries........