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Saturday 19 May 2018

The raised beach platform at Lydstep Point

Looking east

Looking west

This is probably the most spectacular raised beach platform in Pembrokeshire -- it's about 100m long,  and up to 25m wide, and is tucked into the little bay between Lydstep Point and Whitesheet Rock.   It cuts across near-vertical strata, and appears to have nothing to do with any faults or fractures in the Carboniferous Limestone.  It's difficult to photograph because it is so extensive -- but everywhere it has quite a gentle gradient down from a distinct notch cut into the cliff slope, and at its outer edge there is a sharp drop down into the sea.

The most fascinating thing about this platform is that it is incredibly chopped up -- criss-crossed with fissures and chasms and undermined by caves.  It is actually quite difficult to walk across it because of these surface irregularities.  This, to me, indicates very great age --  the chasms, pits and collapsed caves are all signs of marine processes currently destroying something formed a long tome ago, at a time when sea level was rather stable, around 15-20 m above its present level.  I think that this raised beach platform is at a higher level than that of Broad Haven -- which is also cut into a limestone coast.

In spite of a thorough search, I found no traces of a raised beach here (cemented or loose) and no trace of any till.  But there is an area of about 10m x 10m where cemented limestone breccia rests on the platform and has survived subsequent erosion -- storm waves certainly get onto this platform when there is a southerly gale combined with a high tide.


Here the breccia is about 1m thick, and about 2m  thick in a few places -- and it has to be related to the limestone breccia on the neck of the small peninsula just 450m to the west.  The other interesting feature of the platform is the presence of a number of widened fissures and "slit caves" cut into the face of the old cliffline at the bach edge of the platform.  These are perfect locations in which animal remains and maybe other organic materials might be found.  These would be invaluable in working out the chronology of this site.


My instinct is that there might be raised beach cobbles -- and maybe ancient till -- beneath the cemented limestone breccia, waiting to be discovered.  The rock platform itself may even predate the Anglian glacial episode -- but it could of course be a composite feature, freshened up during several interglacial high stillstands of the sea.



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