I have been intrigued by Landshipping for quite some time, and today my wife and I went down there for a walk and a picnic in the winter sunshine........
As mentioned in a previous post, there is a reference, in the Geological Survey Haverfordwest Memoir, p 215, to an interesting section on the shore of the Cleddau confluence, immediately to the east of Oxhouse Farm. The location lies between Landshipping Ferry and Landshipping Quay. Grid ref SN007113. The section at the time of the original survey, a century or more ago, showed:
Gravelly "boulder-clay" with igneous and other erratics
Blue clay with plant remains and quartz pebbles -- related to the raised beach?
Gravelly rubble becoming more angular downwards
Rock platform?
However, on the geological map a spread of sands and gravels is shown, but no till. A section of the map is reproduced above -- see the pink area to the east of the confluence. So is there an extensive spread of sands and gravels overlying till?
After my intrepid expedition I can confirm that there is no spread of fluvioglacial materials here, but quite an extensive spread of till. So the patch on the map has the wrong colour!
The shoreline between Landshipping Quay and Landshipping Ferry. The low cliff is partly masked by vegetation.
If one follows the shoreline from Landshipping Quay round the point and ending at Landshipping Ferry, one finds a gently sloping and undulating sheet of till ending at a low west-facing cliff around 3m high. Bedrock Coal Measures are exposed almost everywhere along the high tide line, although there is much masking vegetation. The sandstones and shales (and some coal layers) are thoroughly rotten. But there are many rounded pebbles and cobbles and larger erratic boulders on the beach, and for a distance of more than 100m there are excellent exposures of sticky clay-rich till (which may be a lodgement till) made up for the most part of old estuarine materials over-ridden and incorporated by ice, and a more silty till packed with pebbles and cobbles up to 10 cm in diameter, with occasional larger boulders. The till is not coloured grey or blue like the fresh Irish Sea till, but it is a buff or reddish colour indicative of considerable weathering. But the pebbles contained are quite fresh in appearance, and there is no sign of rotting. Nowhere does the till appear to be cemented.
The till is seen to be up to 3m thick, with occasional signs of "churning". In the northern part of the exposure, where the till has a lower clay content, there are signs of crude stratification; and in one section we can see a layer of buff-coloured and relatively stoneless "sandloess" up to 15 cm thick. In turn this is overlain by about 30 cms of dark grey loamy soil.
I have to say that in none of the current exposures can we see "blue clay with plant remains" under the till. And neither did I record any "gravelly rubble coarsening downwards". in spite of searching, I found no deposits that I would refer to as slope breccia, either under or above the till. This is not surprising, because there are no steep slopes in the vicinity, and no substantial rock cliffs which could have introduced a ready supply of debris either under a periglacial or temperate climatic regime.
Two exposures of clay-rich till located around grid ref SN007113. The matrix is sticky and weathered to an orange or foxy-red colour. There are some erratic (far-travelled) pebbles, but most are made of Coal Measures sandstones or Millstone Grit.
From the nature of these deposits I suggest that some of them may be lodgement tills and others are more likely to be flowtills. There are close similarities in texture and other characteristics with other tills found around the coasts of west and south Pembrokeshire.
One feature of particular interest is the nature of the terrain to the east of the cliff exposures. On both sides of the road the fields are subject to waterlogging, and this suggests the presence of clay-rich till at the surface. There are small ridges, hollows and swells in the terrain, and this is unusual for south and mid Pembrokeshire. I am tempted to suggest that there is real morainic topography here, indicative of dead-ice terrain. Similar terrain is seen in parts of NW Pembrokeshire, inside the Late Devensian ice limit. So is the Landshipping till sheet of Late Devensian age? I am very tempted to say so, although the location is right in the middle of the "South Pembrokeshire ice-free enclave" about which we have speculated so much in the past.........
The proposed area of Anglian glacial deposits in central and southern Pembrokeshire, thought to have been a Late Devensian ice-free enclave. The deposits described in this post are at the confluence of the two Cleddau rivers, right in the heart of this enigmatic tract of country.
I'm still very puzzled......
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