Some of the ideas discussed in this blog are published in my new book called "The Stonehenge Bluestones" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
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Monday, 24 January 2022

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!

New book on Gower landscape (and water).....

I have recently done a review on this large-format hardback book for a specialist journal, so I won't repeat that here.  But it's very well produced, and packed with excellent maps, diagrams and  detailed info on landscape evolution -- including the events of the Ice Age.  

It's been published privately by Prof Peter Kokelaar, who was at Liverpool University, arising out of his own passion for Gower, the landscape and the origins of groundwater.  The title is rather unfortunate, but there you go......... I'm not sure that all that many people are exercised by the question of whether our water is really ours or somebody else's.

I don't agree with some of the things that he says about the patella beach and aspects of glacial history -- but by and large he has stuck quite closely to the story related in the QRA volume on the Quaternary history of Gower.

Anyway, the book is good value at £20, and I hope it succeeds.  If just a third of the members of the Gower Society buy a copy, he will turn a loss into a profit!  So best of luck to him.

Saturday, 22 January 2022

"There is no evidence.........."

Over and again, these days, we see this phrase:  "There is no evidence that ....."  or  "There is no evidence of....."

One should be very careful about using that phrase -- though I must admit to using it myself all too easily.  For example, "There is no evidence that there was ever a giant circle at Waun Mawn"  or "There is no evidence of stone sockets in the area examined." 

A well-known QC mentioned the other day that in law, once something is claimed as evidence, it is evidence, whether one likes it or not.  It is then down to those who dislike it to counter with contrary evidence, or to scrutinise it very carefully under cross-examination in order to show that the "evidence" does not in fact show without a shadow of doubt that something is the case.

So evidence is defined in law as "data presented to a court or jury in proof of the facts in issue and which may include the testimony of witnesses, records, documents, or objects."  Or as follows: "any information that is presented with the aim of helping the court decide whether or not a crime has been committed."

On the other hand in science, evidence is defined thus:  "......that which tends to prove or disprove something; ground for belief; proof; something that makes plain or clear; an indication or sign."

So when one says "There is no evidence" one actually means "There is nothing that I consider strong enough to be proof!"  

To avoid confusion, we should probably say "There is no evidence that withstands scrutiny" or "There is no convincing or strong evidence to support the claim being made...."

Anyway,  I still think there is nothing at Waun Mawn worthy of being called evidence, in support of the fantastical lost circle hypothesis!

Igneous erratics in the Bristol Channel

Gabbro (?) erratic boulder on the beach at Lydstep, S Pembs

Loveston Farm igneous erratic, probably dolerite, South Pembs.

Following up on some points made by Peter Kokelaar in his new book "All our own Water" (unfortunate title!), I have been checking out the references to igneous erratics on the Bristol Channel coasts.  There are quite a lot of them.  Here are some of the localities:

Flimston Churchyard:  seven erratic boulders in churchyard, and others nearby. A 'brecciated spherulite, albite, trachyte or rhyolite.'  Other volcanic ashes, dolerite and gabbro, from NW Pembs. (Adrian James)

Lydstep, Pembs: gabbro (?) erratic on beach near fresh till outcrop.  BSJ observation.

Loveston Farm: dolerite (?) erratic in farmyard, recorded by Adrian James.

Broughton Bay, Gower: green granophyre boulder from Pembs, and possible Leinster granite. (Campbell and Shakesby, QRA 2015)

Butterslade, Gower:  non-granite igneous erratics from Pembrokeshire, contained in the Patella Beach deposits. (Jenkins et al, 1985)

Ram Grove Beach, Gower: volcanic and dolerite erratics.  (Kokelaar, 2021.)

Hunts Bay, Gower: erratics of quartz dolerite, pink granite and fine grained andesite or basalt of "Irish Sea provenance". (George, 1933)

Reddenhill Farm, nr Pennard, Gower:  a coarse-grained diorite erratic (from northern Britain?).  Grid ref: SS 536 894.  (Kokelaar, 2021)

Western Slade, Gower: several large igneous erratics including a volcanic conglomerate from Skomer Island (?).  Grid ref: SS 484 855.  (Kokelaar, 2021)

Eastern Slade, Gower:  boulders of gabbro and volcanics, probably from Pembrokeshire. (Kokelaar, 2021)

Caswell Bay, Gower:  a dolerite erratic 61m above sea-level, probably from Pembrokeshire.  Grid ref: SS 595 878.  (Kokelaar, 2021)

Pencoed and Ewenny, near Bridgend: igneous erratics in stiff clay.  Storrie collection: more than 20 erratics from the west, including ash flow tuff (Fishguard Volcanics?), basalt from the Skomer Volcanics, rhyolite, Precambrian rhyolitic tuff, gabbro from near St David's Head, ignimbrite from Skomer, volcanic debris flow deposit from Ramsey Island.  Many are striated. (Bevins and Donnelly, 1992)

Cardiff, Ely valley: pyroxenic keratophyre possibly from New Inn, Pembs. (Griffiths, 1940)

Pentre, near Llantrithyd: tuff from north Pembrokeshire. Vale of Glamorgan - south of Devensian limit (Strahan and Cantrill, 1904)

St Athan:  quartz felsite -- north Pembrokeshire origin. Vale of Glamorgan - south of Devensian limit (Strahan and Cantrill, 1904)

Flat Holm:  large pink granite erratic boulder and many smaller igneous erratics, including  feldspar porphyry, feldspar-rich lava and silicified welded crystal lithic tuff. West Pembrokeshire sources? (John, 2015)

Steepholm: Three glacial erratics identified as metamorphic amphibolites (Ixer, letter to Brit Arch 1999)

Lundy Island:  erratics on island plateau, including rhyolite and "miscellaneous igneous erratics" (Rolfe et al, 2012).

Some of the locations mentioned

The erratics (giant and otherwise) on the coasts of Devon and Cornwall have not been properly provenanced.  Some of the dolerites and rhyolites may have come from Pembrokeshire,  but they may also come from further afield -- and I am quite attracted to Kellaway's idea that to the south of the dolerite-bearing stream of the Irish Sea Glacier in Bristol Channel, there was another stream on its southern flank, carrying erratics from as far afield as Scotland.

Giant erratics on the coast of Devon and Cornwall.  The Giant's Quoit at Porthleven and the Freshwater Gut boulder near Croyde.  Origins unknown...........

Friday, 21 January 2022

Guidance on glaciers


 For those who wish they were better informed on how glaciers are created, and waste away, and how glaciers move, these are the guides to look at!  I wrote them on commission some years ago, for the Norwegian Glacier Museum in Fjaerland, and I think they may even still be in print.  But for those who are on the wrong side of the North Sea, the two booklets are also available on Researchgate:

Tuesday, 18 January 2022

Gower, Pencoed and the "Older Drift"

In previous posts I have pondered on the attribution of certain glacial deposits on Gower to the Anglian glaciation -- or to the "Older Drift Glaciation" as it used to be called.  The attributions were dodgy, to put it mildly, because for a period in the 1980's there was an obsession with assigning every deposit to one or another of the "lithostratigraphic" units invented by Prof David Bowen and because of faulty amino acid dating.  I agree with Prof Danny McCarroll and Dr Bethan McCarroll that all of the glacigenic deposits described in the literature on Gower are probably Late Devensian in age -- except maybe for the concreted till in Watch-house Bay and in Foxhole Cove, near Southgate, which could be Anglian.  

I think that the concreted till in that area might be the same age as the concreted till at Black Mixen, Lydstep, and the other concreted deposits at Ceibwr and Witches Cauldron in North Pembrokeshire.

The other South Wales deposit assumed in the past to be of Anglian age is the mysterious glacigenic deposit at Pencoed, not far from Bridgend, which might be linked with the pottery clay worked in the past at Ewenny.  Some of the erratics collected from that area are found in the Storrie Collection, which I have discussed here:

In the Geological Conservation Review volume of 1989, Campbell and Bowen were rather circumspect about the evidence from Pencoed and Ewenny, but the authors of the BGS Bridgend memoir of 1990 were more forthcoming, and it is worth recording some of their text here.

Wilson, D, Davies, J R, Fletcher, C J N and Smith,
M. 1990. Geology of the South Wales Coalfield, Part
VI, the country around Bridgend. Memoir of the British
Geological Survey, Sheet 261 and 262 (England and Wales)
Second edition


The major climatic changes that occurred during the
Quaternary resulted in the southward spread of ice over
much of northern Europe. Several glacial events are known
to have occurred, separated by interglacial or interstadial
periods when the climate ameliorated. Two glaciations, with
an intervening warm temperate interglacial perind, have
been recognised in South Wales (Bowen, 1973a, 1973b,
1974). The deposits of the earliest (pre-Ipswichian) glaci-
ation occur south of the limits of the latest (Devensian) glaci-
ation. The Ipswichian interglacial is recognised from raised
beach depesits, mainly on the Gower Peninsula and in

The glacial deposits of the Bridgend district comprise tills,
morainic and fluvioglecial sand and gravel and laminated
silts and clays. They were mostly deposited during the
Devensian (the ‘Newer Drift’ of Charlesworth, 1929);
however, the occurrence of supposed pre-Ipswichian till at
Ewenny [SS 903 777] and Pencoed [SS 959 817] (Mitchell,
1960; Bowen, 1973a) has been cited as evidence of an earlier
glaciation in the Vale of Glamorgan by ice of Irish Sea origin
(Bowen, 1970, 1973a, 1974). There are no dated Ipswichian
deposits within the district and evidence for the interglacial is
largely circumstantial, being based on the recognition of sup-
posed palaeosols (Crampton, 1964, 1966) of this age
(Bowen, 1970, 1974).

Postglacial deposits and landforms range in age from the
late Devensian, through the Flandrian, to recent times. They
mainly comprise alluvial and head deposits, but also include
the products of contemporaneous coastal processes and man-
made features.


Page 47

These deposits cover most of the north-eastern part of the
district, are present within the main river valleys, and occur
on the coastal tract between Kenfig [SS 790 620) and Porth-
cawl [SS 808 782] (Figure 2). The expanse of glacial drift in
the north-east is generally regarded as part of an end-
moraine of “Newer Drift’ (Charlesworth, 1929) deposited by
a Glamorgan piedmont glacier, the glacial drift of Kenfig is
envisaged as being deposited on the flanks of a second pied-
mont glacier which debouched into Swansea Bay (Charles-
worth, 1929; Bowen, 1970). The glacial deposits of the lower
Ewenny valley, hitherto regarded as remnants of an earlier
(pre-Ipswichian} glaciation (Strahan and Cantrill, 1904;
Mitchell, 1960; Bowen, 1973a, 1973b), occur south of the
limits of the Devensian ice.

The glacial deposits generally consist of gravelly tills, con-
taining lenses of sand and gravel. Fluvioglacial outwash
gravels occur within, and beyond, the limits of the former
Devensian ice-front, forming terraces in places and underly-
ing the alluvium of the main valleys. Laminated silts and clays
occur as lenses within the tills and outwash gravels.


Correlation of glacial sequences

The earliest glacial deposits in South Wales are undated, but
preeded the Ipswichian interglacial. They are preserved at
several localities (Bowen, 1973a, 1973b, 1974), and it is
generally accepted that they were derived from Irish Sea ice,
which entered the Bristol Channel and impinged on the present

Glacial deposits at Pencoed and Ewenny have been
regarded as till of Irish Sea derivation (Mitchell, 1960;
Bowen, 1970, 1975, 1974) from the reputed occurrence of
shelly material and igneous erratics at the former locality
(Howard and Small, 1900; Strahan and Cantrill, 1904).
These deposits have also been cited as evidence that the Vale
of Glamorgan was glaciated during the pre-Ipswichian
period (termed the Pencoed Cold Stage by Bowen, 1970).
The Pencoed deposit, however, has none of the character-
istics of a till, nor is there any indication that it is older than
the Devensian, the laminated sands, silts and clays revealing
evidence of deposition in a temporarily impounded lake that
developed at the margin of the Devensian ice-sheet.

The Ewenny deposit is a complex of till, gravels, silts and
clays. The till contains abundant clasts of Silesian sandstones
and appreciable amounts of weathered chert, probably
derived from Dinantian or Jurassic limestones, but the
occurrence of erratics of undoubted western provenance
(Strahan and Cantrill, 1904) has not heen verified. The till
probably impounded ephemeral lakes, in which the silts and
clays were deposited. The species of foraminifera within the
Ewenny silts and clays are indicators of a temperate, marine
environment. but are probally derived, with the Bristol
Channel as the most obvious source. They may have been
transported and redeposited by westerly derived ice, or
introduced by aeolian reworking of coastal flats exposed dur-
ing a glacial low-stand in sea-level: in the latter case, the
foraminifera give no indication of the source of the ice that
deposited the Ewenny till. The origin of this till is, therefore,
equivocal; it may have been derived from the west during a
pre-Ipswichian glaciation (Mitchell, 1960; Bowen, 1970,
19730, 1974), but equally may have been deposited during
the Devensian, either by ice from the north-east which
penetrated the lower Ewenny valley ahead of the main ice
from, or from westerly devived Devensian ice (Woodland
and Evans, 1964),

There are no further deposits within the district that can
be ascribed to the pre-Ipswichian gliciation, although
circumstantial evidence has previously been cited to suggest
that the Vale of Glamorgan was covered by ice during this
period. It has been suggested that exotic heavy mineral suites
within soil profiles indicated contamination from a relic
cover of glacial material of Irish Sea derivation (Crampton,
1960, 195), but they are more likely to have been intro-
duced by aeolian action. Cobbles of Lower Lias limestone,
within soil profiles overlying Lower Lias bedrock, were
formerly thought to be of glacial origin (Crampton, 1966),
but this is unlikely because they are generally derived by in-
situ weathering of Lower Lias bedrock. The occurrence af
westerly derived erratics in the Ely valley and as far east as
Cardiff (Griffiths, 1939) has not been confirmed (Waters and
Lawrence, 1987), there being a general absence of erratics
south of the Devensian ice front.

There are no proven Ipswichian deposits in the Bridgend
district, but the terra rossa and terra fusca affinities of local soil
profiles have been interpreted as evidence of former warm
temperate climate (Crampton, 1964, 1966), and Bowen
(1970, 1974) has suggested that they are palaeosols of
Ipswichian age. There is, however, no evidence to suggest
that these are anything other than modern soil profiles. The
‘terra rossa’ soils on Newton Down [SS 838 795] are probably
due to the weathering of Triassic bedrock or palaeokarst
horizons within the Oxwich Head Limestone, both of which
commonly impart a characteristic reddening to soil profiles.
The shallow, free-draining “terre fusca" soils on parts of the
Lower Lias outcrop generally reflect the limestone to
mudstone ratios of the bedrock.

It has been suggested (Trenhaile, 1971) that ledges along
the coast, between low tide and 12m above OD, are rem-
nant interglacial shore-platforms. These occur at Sker Point
[SS 786 796], Porthcawl [SS 812 766] and Black Rocks [SS
867 742], but no deposits have been found on them to pro-
vide evidence of their age and, in general, the features
appear to be the result of differential weathering of the Car-
boniferous and Triassic rocks.

The Devensian ice front in the district is broadly similiar to
that previously described (Charlesworth, 1929; Bowen,
1981; Figure 2), In the north-east, ice trom the Glamorgan
piedmont glacier debouched onto the low ground south of
the coalfield, impinging on, and locally overriding, the
Dinantian limestone escarpment on the southern limb of the
Cardiff-Cowbridye Anticline. Devensian ice encroached
onto the low ground north-west of Coity [SS 918 820], but
north of Bridgend was held back by the major escarpment
forming the southern margin of the coalfield. The tills, sands
and gravels in the north-west of the district have been inter-
preted as a complex kamiform morainic belt deposited by
Swansea Bay ice during the Margam Stage of the Devensian
glaciation (Bowen, 1970).


The above is interesting since the authors argue strongly that the Pencoed and Ewenny deposits (exploited in clay pits to serve at least fifteen local potteries) are late Devensian.  If they are right, this would extend the ice cover of the Late Devensian or LGM -- and this would perhaps reinforce the point I have been making about a complete Devensian ice cover of both Pembrokeshire and Gower.

Sunday, 16 January 2022

Granite erratics on Gower

This is an interesting old paper arising from research in Butterslade Bay, Gower, bu a team investigating the contents of the Patella Beach.  The beach is assumed to date from the last interglacial (Ipswichian), which means that any contained erratics must have been carried into the vicinity during the Anglian or Wolstonian Glaciation.

D. G. JENKINS, R. D. BECKINSALE, D. Q. BOWEN, J. A. EVANS, G. T. GEORGE, N. B. W. HARRIS & I. G. MEIGHAN.  The origin of granite erratics in the Pleistocene Patella beach, Gower, South Wales
Geol. Mag. 122 (3), 1985, pp. 297-302.  

Rare pebbles of granite have been discovered in the raised Patella beach at Butterslade, Gower, South Wales. Their petrography, trace element geochemistry and the Rb/Sr whole rock ageof 55 ± 5 Ma confirm that they are derived from the Lundy granite which is about 49 km to the southwest of Gower. Amino acid analyses of fossil gastropods in the Patella beach have provided an age of 210,000 years. Various hypotheses of transportation of pebbles from Lundy and Pembrokeshire to Butterslade are considered. Erratics from Pembrokeshire were probably transported by Pleistocene ice into the area while clasts of Lundy granite were moved by progradation of beach deposits northeastwards towards Gower during glacio-eustatic marine transgressions in thePleistocene.

Note:  Butterslade is a small bay in the far west, difficult of access, just to the east of Mewslade. 

Quote:  Of 100 pebbles examined there was a size range of 1.7-8.8 cm and an average of 4.6 cm, and composed of sandstone (50 %), Carboniferous Limestone (23 %),grit (18%), volcanic and igneous rocks (other than granite) (6%), vein quartz (2%) and conglomerate (1 %); the granite pebbles are very rare and less than 1 %. The pebbles of sandstones, grit and conglomerate are mainly derived from local outcrops of Devonian strata, probably from Rhossili  Downs only 1.5 km to the north and the Carboniferous pebbles are from the rocks on which the beach deposit lies. Igneous rocks identified include an ignimbrite (Ordovician: Pem-brokeshire or Powys), feldspar porphyry (Ordovician: West Wales), porphyritic rhyolite (Ordovician: Fish-guard), quartz enstatite gabbro (Ordovician: St David's Head).

This is interesting.  As expected, most erratics are local, and many of the others are from Pembrokeshire, confirming the overall direction of ice travel during glaciation by the Irish Sea Glacier.
The six granite pebbles that were investigated proved to have come from the Lundy Island granite.  Their presence is a bit of a puzzle.  The authors' preferred explanation is that the pebbles come from an old storm beach in the vicinity of Lundy Island which was pushed north-eastwards in the direction of prevailing winds, over many thousands of years at a time of rising sea level following deglaciation.  Hmmm -- possible.  Let's just say that the jury is still out.......

West Gower Geol Soc memoir 246 (part IX) by Strahan (1907):

Strahan and his colleagues failed to notice any erratics in the raised beach, and found nothing that they could identify as "Older Drift".  However, they did confirm that most of Gower was affected by "Coalfield ice" from the north, except for the extreme west (around Rhossili) and the extreme east (around Caswell Bay).  the glacial deposits they were looking at were those now classified as Late Devensian (LGM) in age.  Here is an extract from page 40:

TN George and various others followed with much more sophisticated analyses of the glacial features of Gower.  But there has been great confusion over the "Older Drift" (Anglian till)  and the "Newer Drift" (Late Devensian till) of Gower.   Everybody assumes that the Older Drift exists somewhere, since erratics from it appear in the Ipswichian raised beach, but where is it?

There must be remnants on Gower, as there are in Pembrokeshire,  but the attempts to determine what is what on the Gower were thrown into complete confusion by Prof David Bowen's obsession with putting "lithostratigraphic" labels onto everything, and by his "aminostratigraphy" which produced what are clearly false dates on all sorts of sediments in all sorts of stratigraphic positions.  The Geological Conservation Review for Wales (1989) was edited and heavily influenced by David Bowen, and that made matters even more convoluted.  He contended that the deposits in southern Gower were for the most part "Older Drift" and those in the northern part were for the most part "Newer  Drift"  -- and a further over-simplification contended that any ice coming from the west was associated with an ancient glaciation while ice from the north (local Welsh ice) was associated with the Devensian LGM.  Geomorphologists from Swansea University have been trying to sort out the mess for 30 years..........

Anyway, with regard to erratics, there is a new book by Peter Kokelaar (2021) called "All our Own Waters" which deals with landscape evolution on Gower and includes sections on the Patella beach and on the process of glaciation.  In Chapter 3 he refers to many erratics and often refers to them as "Anglian erratics" simply because they have come from the west.  He also purports to show a Late Devensian till overlying an Anglian till at Llethrid (SS 533 915) -- but provides no evidence to support the contention.  i am not convinced.   He also reports on a coarse-grained diorite erratic (possibly from northern Britain) at Reddenhill (SS 535 893) and a coarse-grained dolerite erratic found at 61m above sea level at Caswell Bay (SS 595 878), assumed to have come from north Pembrokeshire. He mentions "Anglian" erratics at Western Slade on the shore platform that are purported to include volcanic conglomerate from Skomer Island.

As I have mentioned earlier on this blog,  the assumption that most of the Gower south coast glacial deposits are Anglian is very likely to be incorrect.  Most of the recent work by Swansea geomorphologists points to a complete ice cover of Gower during the LGM.  While it does seem that most of the "western" erratics are found in the far west and far east of the peninsula, it's best to assume for the moment that during both the Anglian and Devensian glaciations Irish Sea ice and Welsh ice lobes were confluent, with an ice margin that oscillated in a fashion still to be worked out!