I have been back to look at those enigmatic deposits at Westdale Bay, on the west side of the Dale Peninsula and about 1 km from the village of Dale. In 1962 the sequence looked like this:
There were glimpses of a raised beach at the time, and above it a mass of relatively undisturbed reddish till was exposed in the flanks of a deep gully, overlain by about 6m of pseudo-stratified "head" containing many erratics. Towards the top of the sequence there was an increasing proportion of sandy loam or sandloess, with a thin soil at the top of the section.
Today the sequence exposed in the gully and above the beach looks like this:
The Dale Valley has been eroded along the Ritec Fault, which is marked by smashed-up Old Red Sandstone beds. So the head of the bay is a real mess -- with rockfalls, slips and debris avalanches all over the place, sometimes making it difficult to discern the Quaternary stratigraphy. But while no exposures of the raised beach are currently visible, the sequence seems to be as follows:
5. Highest in the sequence: modern soil 10 cm - 20 cm
4. Colluvium made for the most part of sandy loam / sandloess -- carried down from both flanks of the valley. Thickness c 3m -- no clear base. Grades down into:
3. Stratified slope deposits made of colluvium, some brecciated ORS bedrock, and redeposited till. Up to 10m thick.
2. Reddish till with a sandy and gravelly matrix and abundant erratics including igneous cobbles and boulders. In places seen to rest directly on bedrock. In places 3-4m thick.
1. At the base, pseudo-stratified slope deposits made of rockfall material and brecciated bedrock, max 2m thickness. May be indicative of a periglacial environment?
One thing to emphasise is that there is no deposit here which I would describe as fluvio-glacial. So I do not see any depositional role for meltwater in this sediment sequence. The lower brecciated slope deposit (lower head) and the till have the same relationship as they do in many other west Pembrokeshire locations.
Flowtills and fluvio-glacial layers are missing here, and there is no evidence for shearing or other structural disturbances similar to those at Abermawr. But why are there no meltwater deposits here, whereas just a couple of km away, at Mullock Bridge, we have a classic kame terrace with thousands of tonnes of sands and gravels laid down by fast-flowing glacial meltwater?
The stratified slope deposits above the till must be the stratigraphic equivalent of the "ribble drift" at Abermawr -- they must be classed as colluvial. But over what period of time did they accumulate? And what precisely were the environmental conditions at the time? These deposits continue to be somewhat enigmatic..........
PS. It's strange that this is a RIGS designated site, and in the citation reproduced below there is no mention at all of the Pleistocene deposits. Enigmatic they may be, but they are clearly important enough to be protected! I might just drop a line to the powers that be......
RIGS 502 : Westdale Bay
Grid ref SM 799058
Statement of Interest