1A Long History of Rhosyfelin:A Geomorphological Perspective (4th version)

Brian John

If you type "Rhosyfelin" into Google, you will find a good many entries, including many from my blog called Stonehenge and the Ice Age (1). For better or worse, the site at Craig Rhosyfelin, not far from Brynberian, has become a key archaeological site -- which is rather interesting, given that there is not much archaeology there.

Map and satellite image from the Wheres the Path? website. The rocky spur is located just to the east of the very tight bend in the road. The initial dig site (2011) was between the two prominent mayflower trees and the rocky ridge. In dig seasons 2012, 2013 and 2014 the excavations were extended beyond the tip of the spur and all the way to the head of the little valley, to the SW. The scrub clearance and excavations now extend over a distance of c 80m. In 2015 excavations extended out onto the main valley floor, beyond the tip of the spur.

Its new-found fame, of course, lies in the fact that some of the "debitage" at Stonehenge has been traced back to this particular rather insignificant rocky spur in the valley of the Brynberian River, a tributary of the Afon Nyfer. The link has been featured in a number of papers by Rob Ixer and Richard Bevins (2) -- all discussed at length in my blog. More to the point, for the past five seasons there have been extensive archaeological digs on the site, with Mike Parker Pearson, Josh Pollard and Colin Richards all involved, along with a host of other amateur and professional archaeologists

2who are all apparently sold on the idea that this is the first proper "bluestone quarry" ever to be systematically investigated. That is the hypothesis, as enunciated in some detail by Prof MPP in his2012 Stonehenge book (3). To me, it looks like a ruling hypothesis, because it has simply been accepted as correct, and has not been tested through independent scrutiny. There have been no published survey reports or peer-reviewed papers thus far -- and this is interesting, given that this project started in 2011, five digging seasons ago.

Why this tardiness? This may be down to the strict veto exercised by the National Geographic Society, which seems to be financing the dig, and which (according to MPP in a talk in Brynberian) does not allow anything to be published without its consent. Presumably it wants a "world exclusive" in the pages of the National Geographic Magazine. Im inclined not to believe that -- after all, MPP has revealed many of the details of the dig in his book, and that presumably was published with a nod from the publishers of the magazine. Also, if anything spectacular really had been found, nobody would have been able to restrain MPP or any of the others involved from going public. There would have been banner headlines and excited press conferences. No -- it is

The 2011 excavation at Rhosyfelin, showing the abandoned orthostat of foliated rhyolite which has come from the adjacent rocky spur. Note the apparent stratification in the exposed sediments. Charcoal found beneath the stone has been radiocarbon date d to the Early Bronze Age, meaning that the stone was not emplaced until later -- ie too late to be linked to Stonehenge.

much more likely that nothing very interesting has been unearthed during five seasons of digging. The dig site has now been restored and reseeded, following the end of the dig.

3We don't know what dating techniques have been used on samples from the site. There are organic materials in some of the exposed layers in the stratigraphy, and we know that radiocarbon dating has been used. But other dating techniques -- including cosmogenic or OSL dating -- may also have been appropriate with a view to working out the sequence of sedimentation. Why have no radiocarbon dates been published? Well, some bloggers suspect a deep conspiracy on this front -- and I have to agree with them that this lack of publication probably means that the sequence of events which is emerging is not particularly favourable to the "bluestone quarry" hypothesis. On the other hand, we now know that there are at least 20 radiocarbon dates for this site, and some of them were revealed by Prof Mike Parker Pearson in a public lecture on 16th September 2015.. They do not confirm the quarrying hypotheis, but suggest an intermittent occupation of this site (probably by hunters) between the Mesolithic and the Bronze Age. We are promised a big paper in December 2015, and trust that all the dates will then be published.

I have never been invited to have a look at the dig, and my one appointment with members of the team was a grave disappointment since they failed to turn up at the agreed time at Rhosyfelin, so my impressions are based on quick visits in the company of others and on a lack of systematic fieldwork. However, I have a good photographic record of the site, and I have listened intently to the presentations given to the general public by MPP and his colleagues. So here is my interpretation of the landscape history of the site. Let's call it a Long History of Rhosyfelin -- since the timescale is indeed a long one, measured in millions of years. In my view this is a Pleistocene site, not a Neolithic one.

THE SEQUENCE OF KEY EVENTS

This, I think, is the history of what has happened to the landscape and landforms at Rhosyfelin. It is intended for use as a working hypothesis, subject to correction and improvement -- and maybe even to falsification, according to the precepts of Karl Popper! If it needs to be dumped in the future, so be it...... and in the meantime, I will welcome comments and corrections.

1. Phase One. Early Days

There was a long period of landscape evolution prior to the Ice Age, during which the main features of upland and lowland were created. The upland ridge of Mynydd Preseli is all that is left of a much more extensive mountainous landscape. We can assume that there were once spectacular alpine peaks here, created during the Caledonian mountain-building episode around 450 million years ago, and then maybe influenced also by the Hercynian upheavals of 350 million years ago. (These are very rough dates -- in reality those episodes were prolonged and complex.) There was much volcanic activity in connection with these upheavals; the Fishguard Volcanic Series of igneous rocks was emplaced around 450 million years ago, within and on top of old sea-floor sediments which now outcrop at the ground surface across much of North Pembrokeshire (4). You can see traces of the mountain-building episodes in the tight folds, faults and shattered rock zones in the cliffs at Ceibwr, Newport and many other locations between Pen Caer and Cardigan. Many of these rocks in the uplands have been eroded away -- maybe because of the frequency of volcanic ashes and flaky rhyolites mixed in with mudstones, shales and thin-bedded sandstones. In a popular terminology, these would be called "soft" rocks. In contrast, the big intrusions of dolerite in the Preseli Hills have been much more resistant to erosion, explaining the rolling upland landscape with a scatter of dolerite (and some rhyolite) tors.

4One of the tumbledown tors of Carn Meini (Carn Menyn). Here the bedrock is spotted dolerite. It has long been assumed that this locality was the main source of the bluestones used at Stonehenge. The assumption has now been shown by geologists to be incorrect.

Why are the tors there? Conventionally, the explanation is that the tors survive because they are made of resistant rocks which are not broken by tight jointing and fractures, whereas the heavily fractured and "softer" rocks around them have been attacked by chemical and physical weathering processes on a more substantial scale. These tors (like Carn Meini, Carn Alw, Carn Bica and Carn Arthur) have probably been present as features in the landscape for at least 10 million years, even though individual rock surfaces on them might be dated as much younger than that -- as seen in the recent paper on the Dartmoor tors (5) where individual slabs seem only to have been exposed to cosmogenic bombardment for between 30,000 and 50,000 years.) We always need to bear in mind that while a tor is being eroded by frost processes and gravitational settling -- and by other processes too -- the surrounding landscape is also being eroded or lowered at a rate that may be equal, or maybe faster and maybe slower!

We should bear in mind that tors at the end of the "preglacial" period were actually quite widespread across North Pembrokeshire. There were tors on the uplands of Preseli, as mentioned above. But they also occurred on Carningli and Dinas Mountain, at Carnedd Meibion Owen and in Tycanol Wood, and in various locations in the Newport-Nevern area. There were also tors further to the west, on the Pencaer Peninsula, on the St David's Peninsula, and at Poll Carn (Lion Rock) and Maiden Castle at the northern end of Trefgarn Gorge in central Pembrokeshire. (We need to be careful about the interpretation of some of these features, because some seem to have been formed originally as islands or skerries when relative sea-level was falling from over 100m to c30m

5above its present level. They are called "monadnocks" by geomorphologists. So marine processes, as well as chemical and other physical weathering processes, have been involved in their creation.)

2. Phase Two. Getting Colder

At the beginning of the Pleistocene or Quaternary Ice Age, around 10 million years ago, the overall distribution of upland and lowland in North Pembrokeshire, and the approximate position of the coastline, were already determined (6). So in addition to the main features of Mynydd Preseli we can be reasonably sure that there was a shallow depression on the northern flank of the mountain, with many small streams draining down into the Nevern Valley. The Brynberian valley would have been a part of this drainage pattern. Were the deep river gorges at Rhosyfelin and Felin y Gigfran present at the time? Probably not, since the whole land surface was probably higher. However, we cannot rule out episodes of river downcutting and gorge development during phases of increased precipitation and runoff, or during periods of low relative sea-level. (Remarkably little is known about climate and landscape history during this period.) Were the tors at Carnedd Meibion Owen and Rhosyfelin present at the time? Probably they were -- and maybe they were substantially larger and more prominent than those which we see today.

3. Phase Three. Ice here and there -- but mostly there

In the period between 10 million yrs BP and 2.5 million yrs BP the climate cooled substantially, and in some parts of the Northern Hemisphere -- in high latitudes and at high altitudes -- there must have been intermittent glacial episodes, as shown in the deep-sea and ice sheet records (7). It is doubtful that glacial ice will have affected West Wales and the South of England at this time -- so probably there will have been a number of periglacial episodes some of which might have lasted for hundreds of thousands of years. During these episodes frost shattering and scree development will have occurred in some localities, and the landform details on tors and steep slopes might have been modified. Generally, debris accumulation in the lower parts of the landscape (valleys and depressions) will have occurred -- but if at certain stages there were periods of rapid snowmelt or episodes of high rainfall, floods might have deepened valleys -- and it is possible that the Brynberian river gorge, for example, might have begun to form at this time. Also, if some of these early glacial episodes were large enough, it is possible that global sea-levels might have dropped to -30m or more, leading to the inevitable incision of rock valleys well beneath present sea-level. The rock floor of Milford Haven and all the other coastal valleys of Pembrokeshire lies well beneath present sea- level -- but we do not yet know whether this is because of many different episodes of deep downcutting or because of just one or two, later in the Pleistocene (8).

4. Phase Four. Glaciation proper

Around 2.5 million years ago, the first well-established glacial episode involving big ice sheets affected the land masses of Western and Northern Europe. Some of the glacial deposits on the continental shelf seem to date from this time, but the first episode to provide investigators with good quality stratigraphic data was the Anglian glaciation, around 450,000 years ago. That was the most intense and most prolonged glacial episode of the Pleistocene, at least in Europe. There was a very large British - Irish Ice Sheet, covering most of Ireland, Scotland, Wales and England (9). So much of the Planet's water was locked into the big ice sheets that sea-level dropped to at least -120m, meaning that the ice streams and glaciers were for the most part land-based, flowing across vast expanses of land that are now submerged beneath the sea. That includes the floor of the North

6Sea, the Irish Sea, Cardigan Bay, St George's Channel and the Celtic Sea.

These western areas bounded by Ireland in the west and Great Britain to the east were occupied by the Irish Sea Glacier, the largest and most powerful of all the ice streams to have affected the British Isles (9).

As realised more than a century ago by geologists like Geikie and Jehu, this glacier received most of its sustenance from the accumulation areas on Ireland, NW England and Scotland, and flowed broadly southwards towards Pembrokeshire before expanding into a great piedmont lobe which flowed SW, S, SE and even E. The glacier also received ice flowing from the Welsh Ice Cap into Cardigan Bay -- and it is a fair assumption that the

surface of the glacier in St George's Channel must have been at around 2000m, sufficient to drive flowing ice across Preseli and the whole of Pembrokeshire, and up the Bristol Channel towards the Mendips and the Somerset coast. There will also have been supplements to the glacier from valley glaciers flowing broadly southwards across South Wales, from the uplands of the Brecon Beacons and the South Wales Coalfield. That "boost" might well have been critical in maintaining

the momentum of the Irish Sea Glacier, whose snout was by now more than 600 km away from its primary source areas.

What was the maximum southern extent of this glacier? Well, from the glacial traces in the landscape and from the glacial deposits which we know about in southern England, we can be quite sure that the ice affected Somerset, Devon and Cornwall. Were the uplands of the Mendips, Exmoor, Dartmoor and Bodmin Moor covered at this time by local ice caps or by the big Irish Sea Glacier? Almost certainly they were glaciated, since we

Global glacial and interglacial oscillations over the past million years. The glacial phases shown did not all affect SW Britain or leave clear traces.

One of the British-Irish ice sheet modelsprepared by Hubbard et al, 2008.Although this model was created for theDevensian glacial episode, it may be a good indicator of the maximum extent of ice during the Anglian glaciation. Note thatCornwall, Devon, and Somerset are largelyice-covered, and that much of Wiltshire isalso submerged beneath ice.

7know that in the Devensian glacial episode (peaking around 20,000 years ago) there was an ice cap on Dartmoor, and an ice edge on the Scilly Isles. The Anglian was a much more intense and extensive glaciation than the Devensian, and unless there were unexplained glaciological differences between the Anglian and Devensian glaciers -- expressed as different bed conditions, rates of ice flow and surface profiles -- it is reasonable to assume that the ice actually reached Salisbury Plain. That assumption is not yet supported by unequivocal stratigraphic evidence, but as discussed many times on the Stonehenge and the Ice Age blog, there are traces of glacier ice having affected the Somerset Levels, the Mendips, and the Bath area -- and if we accept (as I do) that the Stonehenge bluestones and other strange stones found on Salisbury Plain are extremely old glacial erratics, the matter is more or less settled. On the principle of Occam's Razor, we do not need any other explanation relating to the transport of the bluestones.

What about Rhosyfelin? I suggest that when the Anglian ice started to impinge upon the coastal strip of North Pembrokeshire, there was a substantial tor or craggy outcrop at Rhosyfelin, standing prominently above an undulating fluvial landscape which had already been affected to some degree by a prolonged period of periglacial conditions. That is the way it is, prior to all big glacial episodes. We cannot know whether the tor was massive and coherent, or just a pile of tumbledown debris. At any rate, when the Irish Sea Glacier had taken possession of the northern slopes of Preseli and started to flow rapidly across this landscape, conditions were perfect for shearing to

occur within the ice (10), for the entrainment of bedrock blocks up into the body of the glacier, and for transport within the glacier away towards the SE and E. Many of the other tors on the northern flank and summit of Preseli were similarly affected, while areas on the southern flank were affected to a much lesser extent, as explained in other posts on my blog. It may be that hundreds or thousands of tonnes of rock were removed from the Rhosyfelin rhyolitic outcrop in this way. Because the rock is fissile and flaky, and broken up by abundant fissures or joints, the chances of big slabs or blocks of this rhyolite being transported all the way to Salisbury Plain without further damage were not great -- but not impossible. The bulk of transported material must have been in the form of boulders and cobbles

A mechanism for the entrainment of blocks and other debris from locations on the northern flank of Preseli during the waxing phase of the Anglian Glaciation. This phase may not have lasted for very long; at the peak of the glacial episode the landscape at Rhosyfelin might have been protected from glacial erosional processes.

8maybe less than 1m in diameter. Most of it will have been dissipated or ground up in downstream glacial deposits, but some slabs and "orthostats" in protected locations within the ice mass could have been transported for 300km or more without further damage, to be melted out or dumped in due course at the ice edge. I have speculated on my blog that the "entrainment episode" at Rhosyfelin might have been quite short-lived (maybe lasting for just a few decades or centuries) and that for the rest of the glacial episode the site was protected by immobile or very sluggish cold-based ice. (As a general rule, warm-based glaciers with their bases at or near the pressure melting point can flow fast and erode effectively, whereas cold-based glaciers tend to be frozen to their beds or to slide very slowly, making them incapable of much "work" in changing the form of the land surface.)

At the end of the Anglian glacial episode, it's reasonable to suppose that the Irish Sea Glacier wasted catastrophically. The meltwater channel complex of the Gwaun-Jordanston area was probably formed or dramatically modified at this time (10), with huge volumes of meltwater escaping southwards across any low cols that were available, or else being forced to flow south-westwards and then southwards deep beneath the wasting ice surface or actually along the ice edge. Initially, much of the meltwater was flowing subglacially under high pressure, meaning that occasionally it was actually flowing uphill (11). The valleys connected to Cwm Gwaun are classics of their kind, frequently cited in text books and recognized in the SSSI citations which guarantee a degree of extra landscape protection within the Pembrokeshire Coast National Park. Was there a glacial lake impounded against the northern face of Preseli at this time? It's possible, but as yet we do not have stratigraphic evidence which can be brought to bear. But the gorge at Rhosyfelin may well have had its origins at this time, as great volumes of meltwater flowed northwards towards the lower land of Cardigan Bay at a time of chaotic ice wastage -- such as we see on the margins of some Icelandic and Greenland glaciers today.

5. Phase Five. Many Missing Millennia

Following the Anglian Glaciation, over the course of more than 350,000 years, there were several glacial and interglacial cycles, and it is possible that glacier ice might have affected Rhosyfelin again,on more than one occasion. This ice might have come from the north in the form of another Irish Sea Glacier, or it might have come from a small Preseli ice cap, formed as a result of localised extreme cold and high snowfall. We really have no local evidence which we can -- at this stage -- interpret sensibly. But during this long period there may well have been other climatic episodes at least as warm as the present interglacial, and other very prolonged episodes of periglacial conditions with or without continuous permafrost. Over a period as long as this, it is inevitable that Craig Rhosyfelin will have undergone further substantial change, involving the ongoing reduction of the rocky tor and the accumulation of debris around its foot and in the river valley adjacent to it. What about the details of the river valley? They are actually quite complicated here -- and particularly notable are the subsidiary valleys or gullies on either side of the craggy ridge which we see today. They suggest that water has at some stage (or stages) flowed down from the valley side into the gorge, maybe excavating out zones of weakness coinciding with faulted or brecciated zones, or maybe coinciding with the junctions between the rhyolites and adjacent sedimentary rocks.

6. Phase Six. The Last Interglacial

Thus far, we have no evidence of either the climate or the process of sedimentation at Rhosyfelin for the period around 100,000 - 70,000 yrs BP. However, there are abundant signs on the coast that

9at some stage during this interglacial (called the Ipswichian) relative sea-level was higher than it is today, by at least a couple of metres. There are not only raised beach platforms cut across bedrock in many coastal locations, but also raised beach deposits of rounded cobbles, sand and gravels -- sometimes cemented into a hard conglomerate by calcium carbonate and sometimes stained heavily with iron and manganese oxides. The climate was warmer than it is today, with a landscape just as richly clothed with vegetation (12). It may be that Mynydd Preseli would have been quite heavily wooded, in spite of the high exposure and the location in the far west of Wales.

Soil development during the interglacial would have been much more prolonged than that of the present interglacial -- so soil horizons maybe 2m thick would have been commonplace. But in North Pembrokeshire, the chances of any such soil horizons surviving the events of the following Devensian are very slim indeed.

7. Phase Seven. The Devensian Glacial Episode

This episode is conventionally considered to have started around 70,000 years ago and to have run until about 10,000 years ago (13). Now we are getting into the period which we might expect to be represented in the sedimentary sequence at Rhosyfelin. Prior to the arrival of the Devensian ice in this area, there was a long period (maybe 50,000 years) of oscillating periglacial climate. For parts of this period there was continuous permafrost, as indicated by occasional traces of patterned ground including fossil ice wedges and cryoturbation features. When at last the ice of the Irish Sea Glacier did arrive in North Pembrokeshire it created an effective ice dam along the coastline, holding up the drainage of north-flowing rivers and streams on the northern flanks of Mynydd Preseli and leading to the creation of ice-dammed lakes in the Teifi Valley (now well documented in a sequence of laminated lake sediments more than 50m thick in places) and maybe in other valleys as well (14). Various researchers have suggested a series of glacial lake overflows across low-lying cols, leading to the creation of "overflow channels" or spillways -- but the precise sequence of events

is still a matter for debate, and much more evidence of glacial lake sediments is needed before the true story can be told. On my blog site we have had some debate on the question of whether there was a "Glacial Lake Brynberian". If it ever did exist, then the site of Craig Rhosyfelin might well have been submerged beneath the waters. And if there are laminated or varved lake clays to be found anywhere, then they might be found on the floor of the valley adjacent to the site initially excavated by Prof Mike Parker Pearson and his team. In fact, the 2015 dig on the Rhosyfelin valley floor thick clay-rich sediments -- which have now sadly been covered over again following the end of the dig.

A conservative assessment of the Devensian ice edge in North Pembrokeshire, based on the most recent Geological Survey map. Evidence is accumulating to show that the ice of the Irish Sea Glacier was more extensive than this, probably flowing across the whole of the Carningli upland and maybe across the eastern end of the Preseli ridge as well.

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I am now convinced that the Irish Sea Glacier pushed further south than Rhosyfelin and pressed against the northern hillslope of Preseli. I am also convinced that the ice flowed across Carningli, maybe even covering the highest crags, and across Tycanol Wood and the tors of Carnedd Meibion Owen. There are fresh-looking glaciated slabs in many locations, and I think it possible that the ice might even have inundated the highest tors including Carn Meini. More work needs to be done on this, and maybe we will need cosmogenic dating to be employed to answer the question of maximum Devensian ice extent. There may have been several pulses or ice advances within a short period, and as evidence for this I would cite the recently discovered morainic accumulations at Gernos Fawr, Cilgwyn and Pont Ceunant.

So what traces of the Devensian glaciation might we expect to find at Rhosyfelin? Well, one thing we know from a long study of the coastal exposures of Ice Age deposits around the Pembrokeshire coast is that the glacial episode was neither long enough in duration not intense enough to erode away all of the older sediments overriden by the glacier. The "lower head" accumulations of frost- shattered and pseudo-bedded slope deposits may have been partly removed, but plenty of them still exist. So we can assume that they remained deeply frozen and reasonably resistant to erosion by the glacier that came in from the north and north-west -- or maybe at some stage from the north-east as well. We can discount the effects of the short-lived Preseli ice cap which might have occupied the highest parts of Preseli at some stage. That would have been cold-based, thin and almost stagnant, with a very limited capacity for affecting landscape change.

If the ice was capable of streaming across bedrock surfaces and polishing or moulding them, it must also have been capable of some destruction of upstanding craggy outcrops such as that of Craig Rhosyfelin. So delicate crags might have been demolished, rubble might have been moved and maybe dragged away to other locations further south, and a great deal of debris from pre-existing scree banks might well have been incorporated into the basal ice material derived from country already overridden.

We might expect that in particularly favourable locations within the valleys of Afon Nyfer and Afon Brynberian, we might find a sequence of periglacial deposits (possibly with lake deposits above them), and with glacial deposits higher still in the sequence. These deposits will be sedimentologically quite distinct from one another -- and will thus be easy to recognize.

From my observations at Rhosyfelin, I suspect that at the end of the 2012 digging season the archaeologists reached the top of a till layer which incorporates much local material derived from the immediate vicinity. In this regard it appears very similar to the till found all over the land surface of the Newport - Nevern area. Where rhyolites are outcropping, there are rhyolite boulders in the till; where dolerites are outcropping, the boulders and coarse debris are of dolerite, set in a matrix of debris largely derived from soft and flaky Ordovician shales and slates.

Back to the details for Rhosyfelin. It seems to me that on the exposed rock face we have a series of glaciated (in places ice moulded) slabs coinciding with a series of closely-spaced and sub-parallel fracture planes. The broken debris piled up along the base of this face is mostly angular or sharp-edged, but it includes slabs and stones which have been smoothed by erosion, with many sharp edges and corners rounded off. That seems to suggest glacial action or else a short-lived episode of fluvio-glacial activity, with turbulent meltwater flowing down the gully and into the river valley proper. We now know that there are abundant fluvioglacial deposits in the stratigraphic sequence, downslope from the initial excavation site and extending out into the flood plain of the Brynberian River. It is now apparent that the "2012 surface" exposed by the archaeologists

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coincides with the top of a layer of mixed rubble and till, with signs of iron staining and weathering. This iron pan or hard pan is common throughout the Preseli uplands area, and the top of it has no archaeological significance. The till exposed at Rhosyfelin appears to be clay-rich, like many of the other tills in North Pembrokeshire. To me, the colouring might indicate a period of sub-arial exposure prior to the accumulation of relatively fine-grained slope deposits on top of the boulder litter. On the other hand, iron-staining and weathering can occur in the top 50 cm of a clay-rich till layer even when it is buried beneath other sediments which permit easy water percolation. (This can be seen in the cliff section at Abermawr.)

In the 2013 and 2014 digging seasons the archaeologists excavated well into this till layer and revealed the presence of many sub-rounded and sub-angular stones and boulders made of rhyolite, dolerite and other exotic stone types. Its thickness is variable, as one would expect. Striae are difficult to pick up on these rock types, but O rdov i c i an s ha l e pebb l e s a r e s t r i a t ed , and I found one broken bedrock slab with clear crescentic gouges on its surface, suggesting heavy ice movement across this site.

The Rhosyfelin scree / rubble layer which has been interpreted as quarrying rubble by Professor MPP and his colleagues (for reasons best known to themselves) rests against the base of the rock face. When did this scree start to a c c u m u l a t e , a n d w h e n d i d accumulation come to an end? As indicated above, it is possible that some of the broken debris has been in position since the end of the Anglian glacial episode around 450,000 years ago, when the Irish Sea glacier disintegrated. If we

The foxy red hardpan here coinciding with the top of the Rhosyfelin till layer. Note the incorporated erratics of dolerite and other stone types. The erratics are generally smoothed and have their edges rounded off by ice action.

Other erratic boulders and stones extracted from the dig during September 2013. These are mixed here with slabs of local rhyolite removed from the dig site.

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bring our understanding of glacial episodes to bear, we may assume that there were periglacial episodes which followed the melting of the glacier ice, leading to the breakdown of glacially steepened slopes and the accumulation of scree and other slope deposits. In an area like this, subject to compressive ice flow, pressure release mechanisms must have come into play. There may have been no further glacial action in this area until the Devensian; there was at least one other glacial phase (referred to as the Wolstonian or Saalian glaciation in other parts of the world) but if

the Irish Sea Glacier of that time did not extend this far south, then there would have been a prolonged period of cold or periglacial conditions (maybe lasting for 50,000 years or more) during which further breakdown of the Rhosyfelin crags might have occurred. Whether the rock debris fell from above the rock face as we see it today, or from the face itself, we cannot tell on the basis of the current evidence.

When the Devensian ice arrived there must have been a great deal of debris around the Rhosyfelin "spur" -- some of it fresh and some of it having been in place for maybe hundreds of thousands of years. One would expect the oldest material on the site to be stained with iron and manganese oxide. As the ice flowed across the site, some material was overridden in a relatively undisturbed state, some incorporated into the basal layers of ice and transported away, and some mixed up with basal till and erratics transported from the land surface to the north of the site.

The overwhelming impression, from an examination of the relationships between glacial, fluviogracial and rockfall deposits, is that this was a typical dead ice or ice wastage environment, in which almost anything could happen, and probably did............

8. Phase Eight. The Late-Glacial

Probably this site was clear of glacier ice by 18,000 yrs BP. After that, for maybe 6,000 years, the climate remained cold as the great ice sheets gradually wasted away further to the north. We know from the stratigraphic evidence in other parts of Pembrokeshire that there was some redistribution of glacial and other old deposits by solifluxion and slope washing processes, but there were no thick accumulations of "head" as there were in the earlier part of the Devensian (14). But in the period 13,000 yrs BP to 10,000 yrs BP there was a strange "triple event" referred to as the "Late Gacial"

Crescentic gouges on a slab of foliated rhyolite, suggesting that this slab has been subjected to intense pressure by thick over-riding ice.

Fist-sized pebble of grey Ordovician shale, found in the till layer. Both facets and striations are clearly visible.

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and characterised as a cold phase (Zone 1 or Older Dryas), a warmer interlude (Zone 2 or Allerod) and another cold phase (Zone 3 or Younger Dryas). There is still much debate about whether these three episodes are recognizable across the world, or whether they were localised within NW Europe for reasons that are not yet apparent (15). At any rate, they do seem to appear in the Pembrokeshirerecord from other Pleistocene sites, and we can surmise that there were further rockfalls onto the Devensian till surface at Rhosyfelin during the Older Dryas and Younger Dryas, accompanied by solifluxion of broken rock materials from the hillslope on the other side of the gully.

The lowest layer above the till surface at Rhosyfelin is a dark-coloured and fine-grained bed up to 30 cms thick, with many stony and gravelly inclusions and "streaky" bands which appear to be rich in organic material. This might be a l acus tr ine deposit accumulated during a glacial wastage phase, either in a localised small lake within the bounds of the valley (the most likely explanation) or in a more extensive "Glacial Lake Brynberian" impounded between a retreating ice edge and the northern slope of Mynydd Preseli. There is at least one small feature that looks like a fault; and less than a metre away there is something that looks like a small fossil ice wedge indicative of permafrost. In places there are traces of what appear to be involutions or cryoturbation features; they need close examination, for they may also have originated as "loading dis tortions" or injection features resulting from the compression and disturbance of saturated sediments by materials dumped on top of them. This dark-coloured layer has a sharp upper surface, and above it is a brown stony layer full of angular broken debris. Maybe this is frost- shattered material, and maybe not; exposed crags and even rocky outcrops on hillsides break down in this way, with angular fragments being worked from the eroding face by a wide range of processes including root expansion, pressure release, rockfalls and small landslides in periods of exceptional rainfall.

9. Phase Nine. The Holocene Interglacial

When the Younger Dryas ended quite abruptly, the last small glaciers to have survived in the u p l a n d s o f B r i t a i n a l l disappeared. The climate warmed rapidly, and from this point on, for the last 10,000 years or so, the dominant processes on most slopes (including those at Rhosyfelin) have been related to solifluxion under a temperate climatic regime. In the exposures on the flanks of the archaeological dig we can see what appear to be up to six distinct layers -- some with a darker colouring reminiscent of organic-rich soil layers, and others with a buff or foxy brown colour. The darker layers seem to have a greater proportion of silts and

Six distinct layers exposed during the 2012 dig. The three darker coloured layers might incorporate organic materials. In the lower dark layer (which has been sampled) there seem to be permafrost structures including involutions, a small fault and a fossil ice wedge.

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clays in them, and the brown layers have more in the sand and gravel fractions. But the layers are discontinuous, which means that we should perhaps refer to "pseudo-bedding" rather than bedding.

What is the climatic significance of these "layers"? Well, we know that there were climatic oscillations on a small scale during the British Holocene, although correlations across the rest of Western Europe are difficult. These episodes are referred to as the Pre-Boreal, Boreal, Atlantic (also referred to as the "Climatic Optimum"), Sub Boreal and Sub Atlantic periods. The warmest episode (Hypsithermal) seems to have been around 8,000 to 6,000 years BP, and after that, in the episode sometimes referred to as the "Neoglacial" by glaciologists, there were a number of short episodes cold enough for glacier advances in the uplands of the Alps, Norway and Iceland. Around 5,000 years BP, when the earliest phases of Stonehenge were under construction, the climate seems to have been cool and rather wet, but with a slow reduction in rainfall totals over 2,000 years or so.

It may well be that when radiocarbon and other dates have been published for the layers exposed in the Rhosyfelin digging seasons of 2011-2014, a reasonably accurate timescale may be applied to the six (or more!) "layers" -- but for the time being we simply have to say that within the last 10,000 years slope deposits up to 2m thick have accumulated on top of the broken rock debris and glacier-related deposits, as the gullies on the flank of the rhyolite ridge have been gradually filled with the products of ongoing erosion and accumulation. Personally, I would not be too surprised if these sediments were to be found to contain Mesolithic flint flakes or microliths made from the Rhosyfelin rhyolite raw materials. In exceptionally wet periods there may even have been mudflows and slope collapses leading to the redistribution of soil and rock debris -- helping to explain why some apparent "layers" are discontinuous. Not all the rock debris was covered with later solifluxion or slope deposits; close to the rock face many blocks were visible sticking up through the ground surface, or were covered by thick vegetation but not soil. The highest part of the "abandoned orthostat" was only about 20 cm beneath the ground surface when found by the 2011 excavation team.

10. Phase Ten. Human Interference?

Leaving aside for the moment the assumption that all of the rock debris at Rhosyfelin is "quarrying debris" resulting from Neolithic stone extraction activities, the archaeologists have mentioned several features that supposedly demonstrate human interference in the arrangement of stones and superficial deposits:

(a) At least two rounded stones referred to as hammerstones, supposedly used for the shaping of rhyolite orthostats. According to Prof Mike Parker Pearson in 2012, these stones have percussion fractures and other damage on their surfaces, showing that they have been used for striking against softer rock surfaces so as to remove projections or irregularities. Apparently these "hammerstones" have been found among the broken rhyolite rock debris low in the sequence described above. I have not examined them, and so I reserve judgment on whether any surface markings are natural or man-made. (My guess is that they are most likely to be fractures, scratches and chatter-marks typical of erratic stones dragged along on the bed of a glacier -- and indeed there are hundreds of other rounded and sub-rounded erratics as well, including at least two made of quartz, scattered in the rhyolite rock debris, till and fluvioglacial sediments (described in my blog.) Interestingly, these hammer stones have not been mentioned recently.

(b) The so-called "rhyolite orthostat" lying some 5m from the rock face, with its upper surface just

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20 cm beneath the ground surface at the onset of excavation. This elongated slab has caused great excitement, and has been much photographed as "the bluestone which was left behind" by the Neolithic quarrymen. Its dimensions, according to the archaeologists, make it a good candidate for recognition as an ideal Stonehenge bluestone; and they are also quite convinced that it has been shaped. They also argue that it is too far from the rock face to have reached its final resting place naturally. On the other hand, I am not the only observer to have suggested that it looks entirely natural, and that its position is not at all exceptional, lying as it does within the "apron" of broken rock debris beneath the Rhosyfelin crags. It lies on top of other smaller blocks, suggesting that it was emplaced by a more recent rockfall from high up on the adjacent crag. I can see no evidence on the stone of any working with hammerstones or other tools. It is also, at a weight of about 8 tonnes, far too large to be a candidate Stonehenge bluestone. Finally, it is very badly fractured, with one serious fracture running across its upper face. It is obvious that even if it is deemed to be a monolith, it would never survive a journey down to the Rhosyfelin river bank, let alone an epic voyage to Stonehenge.

(c) A number of long thin stones with "worn surfaces" which according to Prof MPP have been used as "railway tracks" along which the "orthostat" has been dragged away from the rock face. He says that some of these elongated stones are still positioned beneath the orthostat, demonstrating that the Neolithic quarrymen were in the process of dragging the stone even further away from the face when the project -- for some reason or other -- was suddenly abandoned. The diggers of 2012 also found fragments of "railway track" stones which had supposedly been broken during the dragging of the "orthostat" across them; and some of these bits were joined together again on the grass for all to admire. I am not alone in considering all of this to be fanciful in the extreme. There are elongated stones amid the broken rock debris, and most of these are not "conveniently arranged" at all. There are broken stones everywhere, and if one was keen enough one could probably reassemble many of them. The wear on the edges and flat surfaces of the "railway track" stones is no greater than that on many other stones scattered amid the scree material. Interestingly, in the 2013 digging season the railway tracks were removed, and were not mentioned in Prof MPPs Moylgrove lecture.

(d) A "stone hole" near the tip of the Rhosyfelin rocky spur, and excavated into the reddish-brown "floor" of the 2012 excavation. It is quite a dramatic feature, almost circular, and about 1m across

Two photos showing the abandoned orthostat and the rock face at Rhosyfelin. The one on the left is from 2011 and the one on the right is from 2012. We can see that some of the fallen rock debris is deeply covered by fine-grained slope deposits and some broken blocks are hardly covered at all -- with some sharp edges projecting through the ground surface.

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and 60 cm deep. We have to assume that it is a real feature, and not an "excavation artifice." Did it at one time hold a standing stone or a massive timber pole? Did it have ritual significance? Or was it something intended for storing food or other items? Could it have been a burial pit? We have no way of knowing more about the use of the pit until further information is forthcoming from the archaeologists. However, one feature that interests me is the occurrence of quite large angular stones in the sides and on the bottom of the pit, indicating that the stone litter at Rhosyfelin does not sit on top of the "floor" but passes beneath it. The significance of this will be discussed in the following paragraphs. Also, because of these stone projections any standing stone or wooden post set into the

hole must have had a much smaller diameter than the pit itself.

(e) Between the "stone socket" and the rocky outcrop near the tip of the spur there is a burnt surface or camping floor which suggests, according to Prof MPP, occupation of this site during the Iron Age. The archaeologists collected charcoal and other organic materials for radiocarbon dating. According to the Brynberian presentations on 18 September 2012, the traces of occupation tie in with the stone socket, although the evidence underpinning that statement was not enunciated. No doubt some attention was given to the history of Iron Age occupation during the 2013 and 2014 digging seasons. As I have stated before on my blog, it is not at all surprising that a site such as this might have been used for many years by hunters and travellers, given that the location lies in a well wooded river valley suitable for hunting and fishing, close to a point where the river could easily be forded even at times of high river flow. Also, the gully on the flank of the Rhosyfelin spur would have afforded protection from wind and rain; and indeed a simple shelter could have been built against the rock face. We await developments on this matter.

(f) In his talks Professor MPP has referred to ghosts or precise locations in cracks or crevices on the Rhosyfelin rock face from which recognisable elongated stones in the stone litter have been taken. I have examined the rock face and see no evidence whatsoever to support this contention that there has been human interference. One crack towards the tip of the spur has received a great deal of attention as a monolith source -- but it is far too narrow for any coherent slab of rhyolite to have been taken from it. (On the other hand, fragments for the making of cutting tools might have come from this location.) Where there are ledges from which orthostats might have been removed, they are all highly abraded, indicating that stones were probably dragged away from them by glacial or fluvioglacial forces, well before any human occupation of this site.

(g) In his 2013 lecture at Moylgrove, Professor MPP showed a slide of a small vertical stone embedded in the ground. It looked perfectly natural to a geomorphologist, but he claimed that this stone and others were deliberately set into the ground as pivots so that bigger stones could be moved across them by the use of levers. He also claimed that scratches or striations on a smaller transverse stone just beyond the downslope tip of the big monolith had nothing to do with fractures or foliations,

The socket or stone hole at Rhosyfelin. Notethat rock rubble is seen in the base and sides of the pit, beneath the ground surface.

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or with ice action. So he concluded that the scratches must have been made by a big orthostat (or several) being dragged across it from the inner depths of the quarry, further upslope. However, examination of this transverse stone shows that the marks are not striations, scratches or erosional grooves. They are outcropping foliations on the rock surface, no different from those on scores of other stones to be found throughout the dig site. They follow the strike of these micro- structures. Examination of the side of the rock shows that the foliations or "pseudo-layers" run within the rock, downwards towards the bottom left of the photo.

(h) It is now clear that in the forthcoming Rhosyfelin paper (due in December 2015) much stress will be placed on the fact that the rock face looks like a quarry face. Well, of course it looks like a quarry face, because for four digging seasons the archaeologists have

The location of the camp site at Rhosyfelin, between the outer end of the rock face and the pit, which can be seen in the foreground. Was it used by hunters, or tool makers, or monolithic quarrymen?

Close-up of the "grooves" supposedly caused by heavy orthostats being dragged across the stone in question. There are indeed grooves, but they coincide exactly with the outcropping foliations on the stone surface. They are perfectly normal weathering phenomena, of no significance whatsoever to the quarrying debate.

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carefully manufactured it, by cleaning it up and removing most of the fallen stones and debris which masked it. So it is yet another archaeological artifice. The steeply-sloping surface we see today does not coincide with a single fracture plane; there are in fact multiple fracture planes, coinciding with the foliations in the rock, and the micro morphology of the rock face is controlled by multiple intersecting fractures in three dimensions. The rock face owes its origins to rock mechanics, and not to Neolithic quarrymen.

(i) One gets the impression from the archaeologists that there is a clearly defined surface or quarry floor on which quarrying activities were carried on during the Neolithic. This floor has a greater clay content than the layers above it, and in places it has a reddish colour which marks it out from the buff, brown and black colours of the sediments above it. I am quite convinced that this floor is y e t a n o t h e r artifice, invented by the archaeologists. As indicated above, it looks to me like a perfectly typical iron pan or hardpan with gleyed till or boulder clay beneath it. Many stones, slabs and boulders rest above this hardpan layer; others are beneath it, and others project through it.

DISCUSSION

This site is fascinating from a geomorphological standpoint because the archaeological dig has revealed a number of features that can be tied in with the known landscape history of North Pembrokeshire. There are many coastal exposures of Pleistocene deposits which can be used to elucidate a complex sequence of events; but there are relatively few inland exposures which reveal a matching stratigraphy. Indeed, the stratigraphy at Rhosyfelin does not match that of Abermawr (for example) in great detail. Nonetheless, we know from comparable exposures that slope deposits incorporating frost-shattered debris take a very long time to accumulate in this environment -- at a rate of maybe one or two metres per 10,000 years in a periglacial climate. (Much faster rates of accumulation are found beneath steep cliffs made of friable rocks including shales and mudstones.) Thus I would be very surprised indeed if all the material accumulated above the "broken rock apron" at Rhosyfelin had accumulated in a temperate climate over just 5,000 years (basing that date upon the assumed time of rock quarrying and stone transport to Stonehenge, using the archaeologists' own chronology.) If such short-term accumulation did occur, where are all the other deposits from the 15,000 years between 20,000 BP and 5,000 BP?

Another fact that suggests accumulation of these post-glacial layers over a long period of time (maybe 20,000 years) is the alternation of various layers (or pseudo-layers) of different colours and textures. It is easiest to explain these by reference to a history of periglacial warming -- namely cold snap > temporary warming > colder snap > final warming in the Holocene or post-glacial period. If we seek to explain these changes or oscillations in sedimentation by reference to the very subtle climatic changes that have occurred over the past five millennia, all sorts of difficulties emerge.

If we assume (for the sake of argument) that the slope deposits that have come from the rising ground to the NW, W and SW of the dig site had started to accumulate prior to the onset of quarrying activity, one would expect major disruptions in sedimentation to have occurred, with the quarrymen using a cleared "floor" which would then have been covered by sediments following the cessation of quarrying activity. Only those involved in the dig will know whether such a break or unconformity in sedimentation has been observed; but I suspect, from an examination of all the photos available from 2011- 2 0 1 5 , that the sediments removed down to the rock surface beneath the Devensian till had accumulated in an unbroken sequence over a very long period of

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time.

My conclusion, from the evidence currently available to me, is that all of the features at Rhosyfelin, with the possible exception of the "camp site" and the strange pit located nearby, can be explained by natural processes operating over many thousands of years -- possibly hundreds of thousands of years. When I look at the broken rock litter, and even at the famous "abandoned orthostat", I see no signs of quarrying or any other human activity (17).

That having been said, there are a number of interesting features of the site which require further investigation and discussion. For a start, the camp site near the tip of the spur (near the outer edge of the slope deposits) seems to have been covered with later sediments up to 50 cm thick; these must have accumulated in the past 2,500 years or so. Do these sediments match the sediments at the top of the sequence further upslope, or are they distinguishable in some way? Do these deposits comprise more sandy, silty and clay-rich colluvial material, as might be expected from relatively recent hillwash processes at the bottom end of a long slope? Hopefully, the site report, when published, will give guidance on this.

There are two alternative scenarios that might resolve the debate about whether there ever was a Neolithic quarry at Rhosyfelin. If there was a discrete episode of rock removal, with human beings levering down slabs of rock from a favourable rocky crag or ridge, we might expect the pre- Neolithic land surface to pass beneath all of the rock debris. In other words, the "apron" of rock rubble and slabs -- including the "abandoned orthostat" -- should rest on a discernible surface of till or other material which might be in contact with a buried part of the rock face. If such an unconformity does NOT exist, then the likelihood of there ever having been a quarry here is much reduced. On the other hand, if the rock rubble passes well down beneath the surface exposed in the 2012 excavation, that means that there has been a long history of occasional rockfalls and continuous debris accumulation along the lines described above. Perhaps, when a full site report is published, an answer will be found to this question.........

We must consider another anomaly. If the "camp site" has been correctly identified and dated to the Iron Age, that means that the ground surface which we can see in the photos dates from around 2,500 yrs BP. .This surface seems to pass BENEATH the big "abandoned orthostat" which has caused so much excitement. That means that the orthostat was emplaced later than the Iron Age, possibly as a result of a spectacular rockfall from one of the higher crags on the rocks ridge. On the other hand the Neolithic ground surface on which our hypothetical quarrymen worked must be LOWER in the sequence than the Iron Age surface, making the archaeological "quarrying hypothesis" even more difficult to accept. It was reported by Prof MPP in a public lecture at Castell Henllys (16 Sept 2015) that a piece of charcoal found beneath the proto-orthostat had been dated to the Early Bronze Age -- indicating that the boulder was emplaced later than that. Therefore, if this was a Neolithic quarry, the dating is about as inconvenient as it could be..........

And finally, if there are indeed fragments of rock in the Stonehenge debitage that have come from Rhosyfelin, is it possible that the site was used for the gathering of rock slabs for tool making purposes -- for example for the manufacture of cutting implements? I would suggest this as a possibility, since the Rhosyfelin rhyolite does present very sharp edges when split or shaped, like other rhyolites. So there is a chance that the site was used by hunters for tool-making purposes -- and maybe even valued as a source of special stone. That having been said, I remain convinced that this site was NOT used for the extraction of monoliths intended for Stonehenge or anywhere else. And interestingly enough, Prof MPP admitted in his 2015 lecture that no rhyolite tools, axe rough-

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outs or even microliths have yet been found at this site.

These notes are provided in a spirit of enquiry, to encourage academic debate and perhaps to feed into the discussions surrounding the 2011-2015 digs. I have provided a working hypothesis which can be disproved, or else modified dramatically through new discoveries. No working hypothesis survives for very long, and I anticipate that this one will be no different. Whatever the outcome of the researches at Rhosyfelin may be, it is certainly a fascinating site. Whether its ultimate significance is geomorphological or archaeological remains to be seen.

Finally, a couple of pleas to Prof MPP and the other archaeologists. When are we going to see your seasonal site reports? And when are we going to see the colour of your evidence? With the completion of five annual digging seasons, we have seen nothing in print or on the web, and have heard nothing apart from rumours about inconvenient radiocarbon dates. You have made some pretty dramatic claims for Rhosyfelin, but thus far we have not seen any published photos of the hammerstones which are claimed to have been found, or of the hard evidence for Mesolithic -Iron Age occupation. There are many people who would like to know how hard your evidence actually is, and who would like to work out for themselves whether this really is a site worth enthusing about or preserving.

REFERENCES

(1) Stonehenge and the Ice Agehttp://brian-mountainman.blogspot.com/There are also interesting discussions on other sites such as The Megalithic Portal. http://www.megalithic.co.uk

(2) Ixer, RA and Bevins RE. 2011. Craig Rhos-y-felin, Pont Saeson is the dominant source of the Stonehenge rhyolitic debitage. Archaeology in Wales 50, 21-31.Ixer, RA and Bevins RE, with a contribution from Pitts, M. 2013. A re-examination of rhyolitic bluestone debitage from the Heelstone and other areas within the Stonehenge Landscape. Wilts Archaeol and Nat Hist Mag, 106 (2013), pp 1-15Richard E. Bevins, Rob A. Ixer, Peter C. Webb, John S. Watson. 2012. Provenancing the rhyolitic and dacitic components of the Stonehenge landscape bluestone lithology: new petrographical and geochemical evidence. Journal of Archaeological Science 39 (2012) 1005e1019Ixer, R.A and Bevins, R.E. 2013. Chips off the old block: the Stonehenge debitage dilemma.Archaeology in Wales 52,pp 11-22.

(3) Mike Parker Pearson. Stonehenge: exploring the greatest Stone Age Mystery, 2012,Simon and Schuster, 416 pphttp://brian-mountainman.blogspot.co.uk/2014/08/review-of-mike-parker-pearsons-2012- book.html.

(4) Bevins, R E, 1982. Petrology and geochemistry of the Fishguard Volcanic Complex, Wales.Geological Journal, Vol.17 (1), p.1-21.Howells, M.F. 2007. British Regional Geology: Wales. British Geological Survey, 230pp

(5) Yanni Gunnell, David Jarman, Rgis Braucher, Marc Calvet, Magali Delmas, Laetitia Leanni,

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Didier Bourls, Maurice Arnold, Georges Aumatre, Karim Keddaouche. 2012. The granite tors of Dartmoor, Southwest England: rapid and recent emergence revealed by Late Pleistocene cosmogenic apparent exposure ages. Quaternary Science Reviews 61 (2013) 62e76

(6) Brian John . 2012. Pembrokeshire Coast Path: Official National Trail Guide. Aurum/Natural England/CCW, 165 pp.

(7) Mangerud, J.; Ehlers, J.; Gibbard, P., ed. (2004). Quaternary Glaciations : Extent and Chronology 1: Part I Europe. Amsterdam: Elsevier, 488 pp..

(8) Tooley, MJ and Shennan, I (eds) Sea-Level Changes (Institute of British Geographers Special Publications) 1987, 416 pp.

(9) Mangerud, J.; Ehlers, J.; Gibbard, P., ed. (2004). Quaternary Glaciations : Extent and Chronology 1: Part I Europe. Amsterdam: Elsevier, 488 pp..The Glacial History of the British Isles during the Early and Middle Pleistocene: Implications for the long-term development of the British Ice Sheet. 2011. Jonathan R. Lee, James Rose, RichardJ.O Hamblin, Brian S.P. Moorlock, James B. Riding, Emrys Phillips, Rene W. Barendregt and Ian Candy. Developments in Quaternary Science. Vol. 15, Ch 6, doi: 10.1016/4

(10) Brian John, 2008. The Bluestone Enigma. Greencroft Books, 160 pp.Brian John, 1970. In Lewis,CA (ed) Pembrokeshire in The Glaciations of Wales and Adjoining Regions, Longman, 378 pp.Glasser, N. F., Etienne, J. L., Hambrey, M. J., Davies, J. R., Waters, R. A. & Wilby, P. R. 2004 (August): Glacial meltwater erosion and sedimentation as evidence for multiple glaciations in west Wales. Boreas, Vol. 33, pp. 224237.

(11) Stonehenges Mysterious Stones, Brian John and Lionel Jackson, Earth Magazine,December 2008. http://www.earthmagazine.org/article/stonehenges-mysterious-stones

(12) JJ Lowe and MJC Walker, Reconstructing Quaternary environments (second edition) Addison Wesley Longman Limited, Harlow. 1997. 468 pp.

(13) Dynamic cycles, ice streams and their impact on the extent, chronology and deglaciation of the BritishIrish ice sheet. online 2008. Alun Hubbard, Tom Bradwell, Nicholas Golledge, Adrian Hall, Henry Patton, David Sugden, Rhys Cooper, Martyn Stoker. Quaternary Science Reviews 28 (2009) 759777.Evans, D.J.A. and Clark, C.D. and Mitchell, W.A. (2005) The last British Ice Sheet: A review of the evidence utilised in the compilation of the Glacial Map of Britain. Earth-Science Reviews, 70 (3-4). pp. 253-312.

(14) Palaeoenvironmental interpretation of an ice-contact glacial lake succession: an example from the late Devensian of southwest Wales, UK. James L. Etienne, Krister N. Jansson, Neil F. Glasser, Michael J. Hambrey, Jeremy R. Davies, Richard A. Waters, Alex J. Maltman and Philip R. Wilby,Quaternary Science Reviews, Volume 25, Issues 7-8, April 2006, Pages 739-762

(15) The Devensian/Weichselian Late-glacial in northwest Europe (Ireland, Britain, north Belgium, The Netherlands, northwest Germany), M. J. C. Walker, S. J. P. Bohncke, G. R. Coope, M. O'Connell, H. Usinger, C. Verbruggen. Journal of Quaternary Science, Volume 9, Issue 2, pages 109118,

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June 1994.

(16) The glaciation of Dartmoor: the southernmost independent Pleistocene ice cap in the British Isles, David J.A. Evans, Stephan Harrison, Andreas Vieli, Ed Anderson. 2012. Quaternary Science Reviews 45 (2012) 31-53

(17) Brian John, Dyfed Elis-Gruffydd and John Downes (2015). "Quaternary Events at Craig Rhosyfelin, Pembrokeshire." Quaternary Newsletter, October 2015 (No 137).

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Manuscript revised 22nd September 2015. This is not intended to be an academic paper. It has been written as an informal podcast or lecture.