The Quaternary sequence west of Mumbles

Slab of concreted raised beach gravels (1) with sandy layers -- now detached from the 

raised beach rock platform.  Probably Ipswichian in age. 

Concreted sandy layers within the raised beach sequence.  Many limestone pebbles but also erratic pebbles derived from pre-existing glacial deposits.

Shell bed of mollusc fragments contained within the concreted raised beach.

On exploring the coast between Limeslade Bay and Rams Tor, to the west of Mumbles, under the guidance of Phil Holden, I came across a classic Quaternary sequence that has probably been described before, but no matter.  The sequence is seen in the cliff face above a heavily eroded raised beach platform -- in fact it is so broken up that it's difficult to see it at all, without standing back a bit in the area submerged at high tide!  The bedrock is all Carboniferous Limestone; above HWM, on the platform, the rock surface of broken up by gullies and chasms, with quite a few caves, while below HWM the limestone surface is pitted with deep and irregular solution hollows and rills separated by very dangerous sharp-edges solution ridges and pinnacles.  Not for the faint-hearted.......

The full stratigraphic sequence:

7.  Sandy loam grading up to modern soil at top of cliff.

6.  Upper slope breccia layer, with sharp limestone fragments mixed with glacial and glaciofluvial materials.  Indistinct -- maybe 50cms thick.

5. Possibly redeposited or remobilised till with signs of glaciofluvial lenses.  Melt-out till?  Up to 1.5m thick.

4.  Apparently fresh till full of erratic cobbles and boulders, mostly derived from outcrops to the north.  Currently inaccessible because of thick vegetation below. About 2m thick

3.  Limestone slope breccia accumulated beneath and old limestone cliff -- from rockfalls and gradual accumulation with some pseudo-stratification.  Up to 3.5m thick.

2.  Concreted sand layer - stained red by iron oxide.  Irregular beds with some interbedding of raised beach gravels.  Up to 2m thick.

1.  Up to 2m of concreted Patella beach gravels with abundant erratics, sand lenses and shelly beds.  There are large rectangular slabs of this concreted material, and they have been separated from the underlying rock platform by solution processes and wave action.

At top of exposure, disturbed meltout till (5) with limestone fragments from slope breccia (6) and at the top, sandy loam c 1m thick (7). Mostly Holocene.

Slope breccia (3) below.  Overlain by fresh till (4) with large boulders and abundant erratics of many shapes, sizes and lithologies. Above that, top right, more mobile till which may represent the meltout layer, with much meltwater influence (5). The till must date from the LGM. 

Red sand layer (2) with rockfall / slope breccia of limestone fragments (3) above.  Around the Ipswichian-Early Devensian transition?

This is a classic Ipswichian - Devensian - Holocene stratigraphic sequence such as we see all around the coasts of Pembrokeshire and also on the Gower coast in multiple localities.  The erratics in the raised beach must have come from pre-existing glacial deposits in the vicinity.

I see no reason to deny that the Mumbles area was overrun by glacier ice during the LGM.  I find the arguments for the "redeposition" or rearrangement of older till deposits at Rotherslade and elsewhere unconvincing, no matter what the fabric analyses may say -- it is common for till to be rearranged and redeposited during the meltout process, and for diamicton layers sometimes tens of metres thick to accumulate over a short space of time -- maybe just a few decades.  I see no reason for any special pleading, and prefer to call a till a till. 

 Erratic boulder in rock rubble very close to the raised beach exposure.  Heavily weathered.  I think it may be a dolerite or gabbro, but care is needed -- Pennant sandstone, assorted quartzites and brownstones from the rocks outcropping to the north look very similar. Petrography needed!