Volcanics at Stonehenge: two more types, two more provenances

One of the figures from the paper, showing the stumps that might be candidates as sources for the volcanic rock fragments.

There is a new paper from our prolific pet rock boys.  The details are below. It now appears that volcanic fragments found in the Stonehenge debitage are of two different types, meaning that they have in all probability come from two different locations on the northern flank of Mynydd Preseli.   TRhe Volcanic Group A rocks are argillaceous lithic tuffs, and the Group B rocks are very hard, rather rare, and contain graphitising carbon.   There are currently no orthostats or stumps that can be identified as the source of the scattered fragments.

Note that these rocks are different from the rhyolites that have come from the Rhosyfelin area or elsewhere.  In addition, in the debitage and in the orthostat collection there are spotted dolerites and unspotted dolerites, and assorted sandstones including the Altar Stone.

There is no new fieldwork here, either in Pembrokeshire or in the Stonehenge area.  The two authors have examined samples already collected from various contexts.

The rock types examined do not speak of wonderful orthostats or tools.  Indeed, the two geologists suggest that the rock type was not a great deal of use for anything.  Rubbish rock?  This suggests to me that the source of the Volcanic Groups A and B materials might well have been a nondescript erratic boulder, rather like many of those which still exist in the bluestone circle.

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Rob A. Ixer and Richard E. Bevins (2016), "Volcanic Group A Debitage: its Description and Distribution within the Stonehenge Landscape". 
Wilts Arch and Nat Hist Mag., vol 109 (2016), pp 1-14

Abstract

The three major groups of debitage found in the Stonehenge Landscape are dolerites, rhyolitic tuffs (almost exclusively from Craig Rhosyfelin) and ‘volcanics with sub-planar texture’. This last group comprises two separate lithological sub- groups namely, Volcanic Group A, friable rocks with abundant white mica and a strong metamorphic fabric, and very rare Volcanic Group B hard rocks that are characterised partially by an unusual mineralogy including graphitising carbon.
Petrography, whole rock X-ray diffraction and whole rock geochemistry suggest that Volcanic Group A is a coherent group representing a single lithology, namely an argillaceous lithic tuff and that it is quite different from Volcanic Group B (including Stonehenge orthostat SH38) and from Stonehenge orthostat SH40.
Spatially, as with the other major debitage groups, Volcanic Group A lithics are widely and randomly distributed throughout the Stonehenge Landscape; temporally, almost none of the debitage has a secure Neolithic context. The debitage cannot be matched to any above-ground Stonehenge orthostat but may be from one or more of five buried and, as yet, unsampled stumps.
The lithology is believed to be from an unrecognised source on the northern slopes of the Preseli Hills but perhaps not from Foel Drygarn as has been suggested.

Conclusions

Although not totally resolved, petrography, whole rock XRD and geochemical analysis strongly suggest that Volcanic Group A is a single but quite variable lithology rather than two separate but related lithologies, namely calcite-bearing and non-calcite- bearing. Evans’s (1945) description of the same/ similar rock types in the (north Pembrokeshire) field suggests that, although they vary in terms of their primary and secondary petrography, they are a single geological unit.

Petrography, whole rock XRD, and preliminary whole rock geochemistry confirm that Volcanic Groups A and B are distinct from each other and also that Volcanic Group A is not related to Stonehenge orthostat SH40.

The use of the terms ‘basic tuffs’ by Howard (in Pitts 1982) and Ixer and Bevins (2010) and ‘calcareous ash or tuff ’ by Thomas (1923) to describe Volcanic Group A (and B) debitage are misleading and poorly describe many of the samples, especially the muscovite-rich ones. Bevins and Ixer (2013) called one such sample an ‘argillic rock with accretionary lapilli’ recognising its phyllosilicate-rich nature. Evans (1945) (from outcrops not archaeological specimens) called similar lithologies vitro-lithic tuffs and his description of them would encompass all the Stonehenge ‘volcanics with sub-planar texture’. It is suggested that the term argillaceous lithic tuff is better for these samples and indeed for all Volcanic Group A samples.

Unlike SH38 and its associated Volcanic Group B samples and SH48 and associated Rhyolite Group E, where debitage can be matched petrographically to a single standing orthostat, none of the potential parent orthostats for Volcanic Group A (SH32c, 33e, 33f, 40c and 41d) have been petrographically examined, making it impossible to relate this debitage to any (or all) of the buried stones.
The temporal and spatial distributions of Volcanic Group A lithics mirror that of the other major non-dolerite debitage, namely Rhyolite A–C (Craig Rhosyfelin). Both have a widespread distribution and are very numerous (Volcanic Group A ~45% and Craig Rhosyfelin rhyolite ~30% by number of all the bluestone debitage) within the immediate Stonehenge Landscape and both occur further away at the Stonehenge Greater Cursus area. The temporal distribution of both is very similar to that for the rest of the examined debitage in that most pieces are found from post-Neolithic contexts, but have been found on the Stone Floor close to the Heelstone area. There appears to be no clear systematic change in size distribution with context/ time for any of the debitage about Stonehenge.

So far, trying to find this lithology in the Foel Drygarn as proposed by Thomas (1923) has been unsuccessful (as has trying to locate and exam the original Part thin section that Thomas relied upon). Hence, it is safer to be guarded about attributing this lithology specifically to the northern slopes of Foel Drygarn. However, on present knowledge the origin(s) of the Volcanic Group A lithics is still expected to be found within the Ordovician volcanic sequences in the north Pembrokeshire area on the northern side of the Mynydd Preseli range probably amongst those outcrops examined by Evans (1945).

Relevant Bevins and Ixer References:

BEVINS, R.E and IXER, R.A., 2013. Carn Alw as a source of the rhyolitic component of the Stonehenge bluestones: a critical re-appraisal of the petrographical account of H.H. Thomas. Journal of Archaeological Science 40, 3293–3301
IXER, R.A., 1990, Atlas of Opaque and Ore Minerals in their Associations. Milton Keynes: Open University Press
IXER, R.A., 1994. ‘Does ore petrography have a practical role in the finger-printing of rocks?’ in N. Ashton and A. David (eds), Stories in Stone. Proceedings 10th Anniversary Conference. Oxford 1993. Lithic Studies Occasional Paper 4. 10–23. London: Lithic Studies Society
IXER, R.A. and BEVINS, R.E., 2010. The petrography, affinity and provenance of lithics from the Cursus Field, Stonehenge. WANHM 103, 1–15
IXER, R.A. and BEVINS, R.E., 2011. The detailed petrography of six orthostats from the Bluestone Circle, Stonehenge. WANHM 104, 1–14
IXER, R.A. and BEVINS, R.E., 2013. A re-examination of rhyolitic bluestone ‘debitage’ from the Heelstone and other areas with the Stonehenge Landscape. WANHM 106, 1–15
IXER, R.A. and BEVINS, R.E., in press (title?), in Parker Pearson, M., Pollard, J., Richards, C., Thomas, J., Tilley, C. and Welham, K., Stonehenge for the Ancestors. Prehistoric Society monograph. Oxford: Oxbow
IXER, R.A., BEVINS, R.E. and GIZE A.P., 2015. Hard ‘Volcanics with sub-planar texture’ in the Stonehenge Landscape. WANHM 108, 1–14
IXER, R.A., WILLIAMS-THORPE, O., BEVINS, R.E. and CHAMBERS A.C., 2004, ‘A comparison between ‘total petrography’ and geochemistry using portable X-ray fluorescence as provenancing tools for some Midlands axeheads’, in E.A.Walker, F.Wenban-Smith and F.Healy (eds), Lithics in Action. Lithics Studies Society Occasional Paper 8, 105–15. Oxford: Oxbow Books

Erratic content of Isles of Scilly glacial deposits

 Modern beach deposit, Gugh Island.  Many of these pebbles have come from old deposits exposed in the nearby cliffs.  There are sandstone and shale erratics in this suite of cobbles -- in spite of the fact that Gugh Island is supposed not to have been glaciated.

Grateful thanks to James Scourse for publishing this information in his 1991 paper:
Scourse, J.D.  (1991) Late Pleistocene Stratigraphy and Palaeobotany of the Isles of Scilly. Phil Trans Roy Soc B, December 1991, Volume: 334 Issue: 1271.
A long time ago, but geological information does not date!  The hand sample identifications were made by JR Hawkes of the BGS Petrology Unit.

Below we reproduce info from the appendices of the paper, relating to the Scilly Till examined at Bread and Cheese Cove on St Martin's Island and to assorted samples collected from the related Hell Bay Gravel.

Above:  features of the Scilly Till

Pebbles identified in hand samples -- Nos 1-56, Hell Bay Gravel

The great range of erratic materials is interesting.  Particularly intriguing are the Lower Palaeozoic sandstones and the red / pink / purple / greenish sandstones and marls  which Dr Hawkes speculates as possibly coming from Devonian outcrops in Pembrokeshire, Devon or Ireland.  Brightly coloured Devonian sandstones are quite widespread, but brightly coloured Cambrian sandstones do not outcrop so frequently, and the most obvious source would be the southern coast of the St David's Peninsula around Porth Clais and Caerfai.  How easy is it to differentiate these from the Devonian sandstones?  As far as I know, nobody subsequently has attempted to work out whether these sandstones have come from Cambrian or Devonian outcrops -- there's an interesting project for somebody.  The samples are apparently still held at the School of Ocean Sciences at Bangor University.

The heavy metal suite from the till is also interesting -- perhaps we could get a view from Myris on that?

Additional information:  Dr Hawkes has also found a 10-tonne erratic block of olivine basalt on Great Crebawethan, one of the western rocks not far from the Bishop Rock Lighthouse, and more than 4 km west of St Agnes. This is reported in Scourse (1991).  Who knows what other large erratics are still to be discovered?

More about the Cuckoo Stone

Thanks to Tony for drawing attention to some new work relating to the Cuckoo Stone and its environs.  Some info is here:

http://www.sheffield.ac.uk/archaeology/research/2.4329/stonehenge07-04

It appears that the stone is a large lump of sarsen stone which originally lay in a solution hollow as a recumbent srone.  It was later extracted from its hollow and erected nearby -- and later fell over again, to remain in position where it can be seen today.  In other words, there is no long distance -- or even short distance -- transport involved.

I was interested to read this from the Stonehenge Riverside Project Report for 2007:

The Cuckoo Stone compares well with the Tor Stone at Bulford, about a mile east of the River Avon. In 2005 excavations demonstrated that this stone was similarly associated with an Early Bronze Age cremation burial – in this case a double Food Vessel burial. It too had been raised from its natural recumbent position which was visible as a solution hollow.

There is another mention of the Cuckoo Stone on Dr Nick Snashall's web site here:

https://ntarchaeostonehengeaveburywhs.wordpress.com/2016/06/09/the-lonely-life-of-the-cuckoo-stone/

Nick mentions that this is the only standing (ie recumbent!) sarsen stone left in the Stonehenge landscape, which of course begs the question "How many might there have been originally, before people started collecting them up and putting them into assorted stone settings or arrangements, at Stonehenge, Avebury and Durrington?  How many solution hollows are there that might once have held sarsens?  We have touched on this now and then, and of course I have expressed the view many times that the builders of Stonehenge collected up their stones (all of them -- bluestones and sarsens) from within striking distance of Stonehenge, and had to give up on the later stages of the project when the supply of stones ran out.  The stones were rearranged many times, but the "grand design" was never completed.

Why was the Cuckoo Stone never collected up and used?  Maybe it was just too much of a shapeless lump, and was rejected as not worth the bother?

As it happens, this very day Nick Snashall is giving a guided tour of the Avebury landscape, including West Kennet long barrow.  Hope it's not as unbearably hot as it was yesterday......

More Abermawr revelations

After the winter and spring storms, even more rock exposures can now be seen along the northern edge of Abermawr Bay (on the western flank of the Pen Caer peninsula).  This is one of the most important Quaternary sites in the British Isles, so anything that adds to our knowledge of past events here has considerable significance.  It is now clear that since I started my research work here in 1962 the coastline has retreated between 10m and 20m.  When I was working here in 1962-65 none of the rock faces exposed in this photo were visible.  All were masked by thick pseudo-stratified slope deposits which I referred to as rockfall debris and "lower head" accumulated during a long period of Early and Middle Devensian cold climate.  The erosional features seen in this photo on the rocky cliffs (caves, stacks, smoothed surfaces, wave-cut notches etc) cannot possibly have been formed over a period of just a few months, so they must be pre-Devensian.  They are ancient "fossil features" -- first buried, and now exhumed.  They must also be older than the Ipswichian or Eemian raised beach which sits on fragments of a wave-cut platform on top of the cliffs.

So the assumption must be that we are now seeing the exhumation of a pre-Ipswichian cliff-line formed at a time when sea-level was approximately as it is today.

Next, the exposure of the Aber-mawr Ipswichian raised beach becomes clearer and clearer.   Here is my latest photo, taken as a long shot from the beach below.

We see a jumble of well-rounded boulders and cobbles, with a maximum thickness of about 1 m, overlain by angular rockfall slabs and gravelly debris and then by lower head.  As far as one can see, the raised beach is uncemented.  It looks very similar in appearance and stratigraphic position to some of the raised beaches in the Isles of Scilly.

Here is another photo, showing where the raised beach exposure is located.  The rock platform exposure is fragmentary and it looks irregular, but there is enough of it exposed now to suggest that it extends for maybe 20m along the top edge of the rock cliff, about 6m above current HWMST.   If erosion continues at the present rate, it will soon be possible to scramble up to it and examine it in much greater detail.

The raised beach is exposed at the top of the rock cliff,just above the centre of the photo, in a 

slight gully.

Exploring Avebury - the essential guide, by Steve Marshall

This is a fabulous new book from Steve Marshall, beautifully organized, filled with stunning images and with enough hard information to keep everybody happy.  Steve's cool and laid-back approach comes through in the text, which is clear and concise -- thankfully there is an emphasis on what we know rather than on what we would like to know.  So fantasy is kept at bay, and what we have in its place is a highly informative portrait of a fascinating place which almost everybody seems to prefer to Stonehenge.

In reading through the text, I was greatly taken by the section on sarsen "drifts" (p 14), and the images of the Valley of Stones on Fyfield Down are both atmospheric and revealing.  Then there is a good section on the mode of formation of sarsen stone.  On p 41 there is a fine section (again illustrated by gorgeous images) on the West Kennet Long Barrow.  This is one of the most interesting long barrows in Britain, not least because it is so old -- it's assumed to have been built almost 6,000 years ago.  This is one intriguing quote:

In today’s restored monument, virtually all the sarsen stone is original. However, the original construction also included sections of dry walling made with small, thin slabs of limestone imported from outside the area, as commonly found in other Cotswold-Severn long barrows. Much of the stone used as dry walling in the WKLB was identified as originating from Calne, 7 miles to the west; some though, came from an area between Frome and Bradford-on-Avon, some 20 miles to the south-west. Well over a ton of this ‘foreign’ stone had been imported to build the barrow.

As at Newgrange, it seems that the big stones were used more or less where they were found, and infilling or facade materials were carried in from a few miles away.   That would not have been a major task -- but one is of course quite justified in wondering whether some of the small stones might be erratic material, carried in by ice from the west........  some of the infill slabs and blocks look quite fresh, and Steve mentions that around a tonne of original (Neolithic) material was so rotten by 1950 that it was replaced by new dry walling stone brought in from Calne.  Some of the small slabs look to me (in the photos) to be very worn -- I wonder whether stone shapes and abrasion features have ever been systematically studied?

On p 64 there is a useful explanation of how the stones in the main Avebury stone settings were emplaced.  Steve cites the geophysical work of Martin Papworth in identifying a hundred or so buried stones and also sockets assumed to have held monoliths at some stage; but since the majority of the standing and recumbent stones appear to have come from the immediate neighbourhood, some of the holes interpreted as "sockets" might of course simply be extraction pits.  These are difficult to tell apart without physical examination -- and even then, the task is not an easy one.

On p 104 there is a chapter called "Where did the stones come from?  Again, this is comprehensive, well illustrated and quite revealing.  Good geology, simply explained.  The ten "primary stones" are assumed to have been used more or less where they were found, but the abundant "henge stones" are thought to have been brought in as batches with certain physical differences (colour, texture etc) from sources not far away.  On p 109 there is a good section on possible extraction pits.  The author is not particularly keen on confrontation, but he does suggest (ever so politely) that there is no evidence to support the widely-cited Atkinson theory that the Avebury sarsen stones were carried to the site by heroic Neolithic stone-hauling squads from the Marlborough Downs......

Silbury Hill and lots of other features in the Avebury landscape are also dealt with in detail -- there is far too much to cover in a short review.  But buy the book!  It's very informative, and Steve deserves our congratulations.  And even if you are not into detailed archaeology, buy it as an essential piece of archaeo photographic porn to share with your dinner guests!  I hope it sells well.

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First published 2016
The History Press, The Mill, Brimscombe Port, Stroud, Gloucestershire, Gl5 2QG www.thehistorypress.co.uk

isbn 978 0 7509 6766 2
soft cover, 226 x 248mm, 144 pages, full colour,  £14.99

From Steve's site:
http://www.exploringavebury.com/

"Exploring Avebury is really excellent, being quite clearly the best current introduction and guide to the whole monumental complex: up to date, consistently fair-minded, and superbly illustrated."

Prof. Ronald Hutton, historian

Avebury in Wiltshire is best known as the world’s largest stone circle, but surrounding it is a wealth of ancient monuments. Captivated by its unique atmosphere, many visitors form a personal, often spiritual, connection to Avebury and its ‘sacred landscape’. What was it that first attracted people to the Avebury area more than five thousand years ago?

Beautifully illustrated with over 400 photographs, maps and diagrams, Exploring Avebury invites us on a journey of discovery. For the first time the importance of water, light and sound is revealed, and we begin to see Avebury through the eyes of those who built it.

"Not only is this the most beautiful book to be published on the Avebury landscape, but it offers the reader one of the finest introductions to a region remarkable for its stunning prehistoric heritage and understated natural beauty. Steve Marshall has followed in the footsteps of an earlier generation of great Avebury observers and writers such as William Stukeley and A.C. Smith, to produce an account rich in stunning imagery, detailed personal observation and insightful interpretation. This is the essential guide!"

Dr Joshua Pollard, archaeologist and author 

Whether you are new to Avebury or are a seasoned visitor, this book really is essential. For first-time visitors it is an ideal guide for navigating the Avebury landscape and its monuments; for those who think they already know Avebury, there are surprises in store.  Packed with hundreds of gorgeous photographs, the book shows Avebury not just in the summer, but throughout the seasons. Although Avebury sees few visitors in the winter, it is then that its springs and rivers begin to flow and the place comes truly alive. 

Author Steve Marshall lived close to Avebury for many years whilst researching and taking the photographs for this book. His acclaimed study of Avebury’s springs and rivers resulted from many months of dedicated fieldwork, largely conducted in freezing weather.

Why was Avebury built where it is? Where did the sarsen stones come from? How does Silbury’s ditch fill with water each winter? What was the Avebury landscape like in prehistory? Exploring Avebury: The Essential Guide contains a wealth of new information and examines some of Avebury’s greatest mysteries afresh.

Exploring Avebury includes all the monuments and natural features of the 'sacred landscape' within a five mile radius of the Avebury Henge, including:

• West Kennet Avenue
• Silbury Hill
• West Kennet long barrow
• The Sanctuary
• Longstones
• Windmill Hill
• Marlborough Mound
• Beckhampton Avenue
• West Kennet Palisaded Enclosures
• Devil's Den
• Adam's Grave
• East Kennet long barrow
• Fyfield Down Valley of Stones
• Piggledene
• Lockeridge Dene
• Alton Yew & Springs
• Swallowhead Springs
• and more...

South Downs field systems -- are they really from the Bronze Age?

There has been much coverage in the media in the past week about the LIDAR imagery revealing ancient field systems near Arundel, within the South Downs National Park -- in areas now thickly covered in forest.  The press got very excited and flagged the field systems up as Bronze Age.  They are certainly very extensive and are wonderfully revealed in the LIDAR imagery,  but I cannot see anything in the press release to suggest that they are pre-Roman.  The only info in the press release is this:  "evidence suggests that they (the field systems) go back much further to before the Roman settled here."  What is the evidence?  Does anybody know?  It seems more likely to me that the pattern of field boundaries picked up in the imagery is the Roman pattern as it looked when the Romans left and Britain descended into some sort of chaos -- I would suspect that the pattern inherited by the Romans was much simpler, and on a much smaller scale.


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Mysterious prehistoric farmers and missing Roman road revealed

https://www.southdowns.gov.uk/mysterious-prehistoric-farmers-and-missing-roman-road-revealed/


July 12, 2016

Decades of speculation on the route of a Roman road in southern England have ended but the research which confirmed its location has revealed the extent of prehistoric farming on the South Downs before the Romans arrived.

The discoveries were made after airborne laser scanning (LiDAR) technology was used to map part of the South Downs National Park hidden under woodland for hundreds of years. The work is part of Secrets of the High Woods, a three-year community archaeology project, supported by the Heritage Lottery Fund, led by the South Downs National Park Authority in partnership with Chichester District Council and Historic England.

Trevor Beattie, Chief Executive of the South Downs National Park Authority, said:
“The LiDAR survey lets us peel back the woodland cover from National Park to reveal archaeology both hidden, and protected, by the trees. One of our biggest findings is the discovery of a vast area farmed by pre-historic people on an astonishing scale. Archaeologists are going to have to rethink the human story in this part of the country.”

James Kenny, Archaeology Officer at Chichester District Council, said:
“It’s exciting to see such extensive field-systems so well preserved which have probably lain untouched since the Romans left 1,600 years ago. But evidence suggests that they go back much further to before the Roman settled here.

“The find raises so many questions. Who was growing these crops and who was eating all of this food? We haven’t found signs of settlement so where were they living? The scale is so large that it must have been managed, suggesting that this part of the country was being organised as a farming collective on a very large scale.

“The degree of civilisation this implies is completely unexpected in this part of the world at this time – something closer to the Greeks, Romans and Egyptians than current views of pre-historic Britain.”

When Britain was conquered in 43 AD, a great construction project took place across southern England which resulted in a network of roads – many of which survive to this day. For decades archaeologists and historians have speculated that there must have been a Roman road leading eastwards from Chichester towards what is now Brighton. The project has confirmed that Romans heading east would have left Chichester on Stane Street before branching east and following a typically straight course towards Arundel through Binsted Woods.

Helen Winton, Aerial Investigation Manager at Historic England, said:
“The recognition of the ‘missing link’ in the Roman road west of Arundel, by Fiona Small at Historic England, was a highlight in a project full of exciting results.

“The interpretations and mapping from the LiDAR and aerial photographs by the Historic England and Cornwall Council National Mapping Programme (NMP) teams clearly demonstrated what was long suspected – the South Downs National Park has one of the most remarkable archaeological landscapes in England in terms of the range, extent and time depth of the archaeological earthworks preserved in the woodland.

“The better understanding of the area provided by the project will greatly inform future management of this valuable resource.”

Stuart McLeod, Head of HLF South East, said: “Thanks to National Lottery players, this project has opened up the wonders of archaeology to many more people and it’s fascinating to now see the results of the in-depth work that has been taking place. The research sheds new light on the history of this area and will also help to ensure its protection in the future.”

Find out more in the Secrets of the High Woods exhibition, currently on tour across the South Downs National Park.

Felin y Gigfran and Castell Mawr LIDAR

Thanks to Dave for drawing our attention to Lle -- a Welsh Government web site on which we can see LIDAR imagery for many parts of Wales.  Above is one composite image extracted by Dave -- showing part of the Afron Nyfer valley.  Click to enlarge.  The letters are inserted by Dave.  His notes:

The meltwater channels show up very well (A), but are there other features more like pre-glacial cut-off valleys at the points I’ve labelled B.  What about what looks like a terrace at C, on the Afon Bannon upstream of Pantyglasier.  It has always looked like it when driving, but not so on the lidar as there are other incised cuttings at D.  How did the flat valley floor develop in places on the Bannon and the Nanhyfer?   Is this some form of glacial meltwater down cutting followed by a period of alluvium buildup?

http://lle.wales.gov.uk/GridProducts#data=LidarCompositeDataset

Yes, the meltwater channels do show up very well, and they are highly complex.  The course of the Nyfer has changed many times as a consequence of glacial diversions and valley blockages by morainic and other materials.  Much work has been done (not by me) on recognising the pre-Devensian course of the Nyfer and comparing it with the post-Devensian course.  The biggest dry valley section is near Nevern itself, where the modern river runs in a great loop to the north of the old valley.  I agree with Dave that the sites lettered A are all glacial meltwater channel sections; and yes, the bits labelled B may be interglacial (not pre-glacial) sections -- but they are more likely to be dry channels used subglacially during the Devensian.  I would need to take a careful look at them to be sure.  The features marked C and D are interesting -- will try to take a look at them some time .......

Unfortunately, there is no LIDAR coverage for Rhosyfelin and Pensarn -- both sites lie just off the bottom of the image shown above.  But take a look at the fantastic detail on the images shown below -- all from the Felin y Gigfran - Castell Mawr area.

The uppermost of these images has OS map data superimposed, including contours and place names.  Note that in this one small area there are three prehistoric features -- Castell Mawr is the big circular earthwork.  Castell Llwyd (the westernmost settlement) is a fortified site on a spur above the river, and we can see another simpler fortified site (called Cwm Pen-y-Benglog Camp) on another spur south of Castell Mawr and close to the Felin y Gigfran nature reserve.  Both of these could be labelled as "promontory forts" and they are most likely to be from the Iron Age.  But who knows?  These days many "Iron Age" forts are being found to have much older origins........

In the Nyfer Valley itself, the big flat terrace to the SW of Castell Mawr must be an old valley floor into which the modern valley has been incised.  There are several features here suggesting subglacial meltwater flow;  in the middle image, look at the elongated rocky spurs inside the main valley.  Do they remind you of anything?  Just think Craig Rhosyfelin...........

Gors Fawr stone circle

Since there is a bit of interest in Pembrokeshire stone circles just now, in the light of the hypothesis that there was a proto-Stonehenge somewhere or other, here is a reminder of the fact that this one -- at Gors Fawr, near Mynachlogddu -- is the only one worthy of the name.

This is one of the best images of it -- taken by my son Martin and used on the cover of a glossy book which I published in the year 2000.  Don't try to get a copy, since it sold well and went out of print very quickly..........

But the Gors Fawr circle is really rather feeble, made of very small stones, and if this is the best we can do in Pembrokeshire I suggest that there was no great tradition of building stone circles here in the Bronze Age, let alone in the Neolithic.

By the way, this stone circle is very well documented.  Plenty in the literature about it.

The Pensarn Treasure Hunt site? (revised)

This is the field near Pensarn (near Crosswell) where the digging action might be concentrated this year in September, when MPP and all the other boys and girls roll up for the annual Pembrokeshire dig.   At least, we think this might be the field, if several little birds have tweeted the right info towards us, and if Hugh is right.  The grid reference is SN 123359.

Not sure whether all those things we can see are bales of straw, animals or boulders -- must get over there one of these days and take a look.  Maybe Hugh can enlighten us?  Apart from these prominent features on the photo, there do not seem to be any traces of patterns in cropmarks, parchmarks or subtle shadows showing raised surface features or hollows.  All very intriguing.

Modification with extra images:

The blobs on the image clearly were animals! 

Thanks to Simon K for alerting us to the much better definition on Bing Maps.  Here are two images from the Bing web site.

Two further images of the same field.  On the top image, with the sun in the south, a more or less circular mound can be seen to the east of the tree with a shadow, with a slight shadow on its north flank.  It is approx 25 m across.  On the lower (oblique) image, with the sun low in the west, the mound shows up even more clearly, just at the tip of the elongated tree shadow.  Courtesy:  Bing Maps.  

Now this starts to get interesting -- not at all what I expected.  Round mounds like this are normally from the Bronze Age;  the earlier Neolithic mounds (mostly stripped away in Pembrokeshire to expose the dolmens or passage graves that were partly within them) were generally elongated.  They would be called "long barrows" in Wiltshire.

So what might this feature, of probable Bronze Age origin, have to do with Stonehenge and Rhosyfelin?  We can be pretty certain what the working hypothesis for the September dig will be, from some of the things said by Prof MPP and others.

It'll be on these lines:

1.  Stones were taken from the supposed quarry at Rhosyfelin, hauled up out of the Brynberian Valley via the little cwm to the east of the rocky spur, and then across country for about a kilometre to the slight rise near Pensarn, to be put up as a bluestone circle with a diameter of c 25m.  Date:  probably around 5,500 yrs BP.

2.  The circle (which also included stones from Carn Goedog) became greatly revered as a sacred site -- maybe cremated bones were placed into stone sockets prior to the placement of the monoliths, as in some of the Aubrey Holes at Stonehenge.

3.  The bluestone circle was dismantled and hauled off to Stonehenge, still during the Neolithic.

4.  Later, in the Bronze Age, the sacredness of the site at Pensarn was confirmed by the building of a round barrow or burial cairn, which is still in place although greatly denuded over the passing of the millennia.

We can but hope that this will be treated as a working hypothesis rather than a ruling hypothesis;  given the track record of this particular group of researchers, I am not very confident on that score............. 

Needless to say, a huge amount of hard evidence would have to fall into place if this hypothesis is to have any chance of standing up to scrutiny.  Ever more intriguing.......

The invisible geomorphologists

Almost a month after my post about the invisible geomorphologists and glaciologists who supposedly think the MPP quarrying hypothesis is very convincing and that  the interpretations of the local geomorphology by Dyfed, John and myself are dodgy, we haven't heard a whisper from anybody.  All we have to go on are nudges and hints from people who themselves refuse to give their names, in comments on this blog.  Whoever these "experts" are, they are still hidden somewhere in the undergrowth or behind a frosted glass screen.  Very timid and demure, they are, to be sure........

http://brian-mountainman.blogspot.co.uk/2016/06/the-strange-case-of-invisible.html

Until somebody publishes and puts their name to a proper reasoned critique of our two papers and shows them to be at fault, we will have every right to assume them to be reliable and even authoritative.  Enough of ghosts and anonymity.  And when are the members of the Quarrying Cult going to abandon the cowardly practice of simply ignoring everything that does not happen to be convenient to their fantastical story?

The hunt for Proto-Stonehenge and the Holy Grail

Acknowledgement -- Google Earth image.  The farmed area to the east of Pont Saeson.  Pont Saeson is near the west edge of the image.  Rhosyfelin is top left.  The main road is clearly visible.  The "target" area is to the east of the minor road.  The farm shown bottom right is Pensarn.

More from the rumour mill.  We have had many posts before on this topic -- just look up "Bedd yr Afanc" and "Proto Stonehenge" by using the search box.  The set-up for the latest search (due in September) has been carefully planned; as the "evidence" for quarrying at Craig Rhosyfelin and Carn Goedog has been challenged and found wanting, the stakes have been raised and the Neolithic fantasy about those heroic quarrymen and monument builders has become ever more elaborate.  So now everything hinges on the discovery of the place where Stonehenge (or at least the bluestone part of it) was initially erected before being dismantled and removed in a proto-Ikea operation.  The thesis is that it is somewhere on dryish ground between the two "quarry" locations........

I have previously assumed that it is likely to be at Bedd yr Afanc, and some work has also been done in the vicinity of Tafarn y Bwlch;  but now a little bird tells me that the 2016 dig might well be in quite a different place,  south of the main road on the farmed land between Rhosyfelin and the upland common.  A satellite image of the general area is shown above.

The only clue we have on this closely-guarded secret is this:

From the recent press release that accompanied the publication of the 2015 "Antiquity" article by MPP et al:  "Prof Kate Welham, of Bournemouth University, said the ruins of a dismantled monument were likely to lie between the two megalith quarries. “We’ve been conducting geophysical surveys, trial excavations and aerial photographic analysis throughout the area and we think we have the most likely spot. The results are very promising. We may find something big in 2016,” she said."

So there we have it.  If you can see anything interesting on the above imagery, you are a smarter air photo analyst than I am -- but it will be interesting to find out (a) where exactly the site is, and (b) what "very promising" things have been turned up in trial digs and geophysical work.  Fantasies or facts?  All info gratefully received.  Watch this space......

The Stones of Stonehenge

 Acknowledgement:  Anthony Johnson

Simon Banton's excellent site is getting better and better all the time -- it is now really very informative, and I hope that it will attract comments from others who hold information about particular stones.  Congratulations to him, and thanks for all the hard work!
 
http://www.stonesofstonehenge.org.uk/p/about-this-site.html

Simon has added a comment on the missing stones and the parchmarks:

Four sarsen stones that might be expected to complete the sarsen circle are also missing (eg Stones 13, 17, 18 and 20) and so those stones do not have pages either. Evidence that the sarsen circle was intended to be complete arose during the dry summer of 2013 when a series of parch marks appeared in the circuit exactly where some of the missing uprights should be.

Simon Banton, Mark Bowden, Tim Daw, Damian Grady and Sharon Soutar (2014). Parchmarks at Stonehenge, July 2013. Antiquity, 88, pp 733-739. doi:10.1017/S0003598X00050651

I note that he uses the words "evidence that the sarsen circle was intended to be complete......." rather than saying "evidence that the sarsen circle was complete......."    I'm happy with that, since as I have said before, the fact that there may have been pits in the places designated does not actually mean that they ever held stones -- and so the evidence cannot be taken to show that Stonehenge was once a complete monument.

Acknowledgement:  Simon Bowden

New Coflein web site for Welsh archaeology

There is a new Coflein web site -- published by the Royal Commission and the Welsh Government -- which allows access to all of the records relating to national monuments, including the key archaeological sites in Wales.

Here are some links:

New Coflein web site
http://www.coflein.gov.uk/en

Carn Meini record
http://coflein.gov.uk/en/site/401672/details/carn-menyn-bluestone-outcrops-of-spotted-doleritecarn-meini

Rhosyfelin record:
http://www.coflein.gov.uk/en/site/416247/details/craig-rhosyfelin-pont-saeson-craig-rhos-y-felin-rhyolite-bluestone-outcrop

This is a very useful resource, although some bits of it are actually the remnants of the old site, and there are still large numbers of photos etc which are NOT available online and which can only be consulted at HQ or else ordered and paid for.  This is all rather frustrating, and my impression is that the English Heritage site is better and rather more open in allowing free access to specialised materials........ it will be interesting to see what others think.

I haven't looked at many site records yet, but if the records for Carn Meini and Rhosyfelin are anything to go by,  some serious revisions are already needed.........

Henry Patton's Welsh Ice Cap animation

I have referred to this before -- but for some it was difficult to get at, needing extra plugins etc.  This is a relatively easy way to look at the reconstruction of the waxing and waning of the Welsh Devensian ice cap.  You should be able to go straight to the video on Henry's web site.

http://henrypatton.org/2011/the-welsh-ice-cap

Note that this is the second of Henry's animations, for which he reduced temperatures by 0.2 deg C.  the result of that was the introduction of an earlier expansion phase which culminated in a big and very ephemeral ice cap around 30,000 years ago.  There is much debate about whether this happened or not.  On the same web page you can see the other animation as well, which incorporates just one big expansion phase culminating around 23,000 years ago.  In this animation the ice melts away very quickly, and is almost gone (except for remnants in the high mountains) by 18,000 years ago.

The other thing that will surprise many people is the great speed of ice cap development -- as in the case of the larger ice sheets, all you need is somewhere between 5,000 and 10,000 years to build a huge ice mass from scratch.

Ice in the Celtic Sea -- piedmont glacier or ice stream?

 These maps (which I published in 2011) show the alternative hypotheses for the glacier ice affecting the Celtic Sea.  There are inaccuracies on both maps, as recent publications have shown.

Below I reproduce the latest info from the BRITICE-CHRONO site, reporting on the ongoing programme of work.  Fascinating stuff!  As we can see, as the ice edge adjustments are being made,  there is a recognition that the ice that affected the Scilly Isles came from the NW and not from the NE (as would be required if an Irish Sea ice stream had affected the islands.  That accords with my observations on the islands, which I hope will be published before too long.

I have discussed this issue several time before, for example here:

http://brian-mountainman.blogspot.se/2011/04/whats-in-name.html 

If the ice really did flow from Ireland as a piedmont lobe, one might expect to find southern Irish erratics in the glacial deposits left behind.  I begin to suspect that there is truth in both scenarios.  Maybe there was a piedmont lobe during the early part of each glaciation, followed by a dominant ice stream towards the glacial maximum?

The other thing that I still have difficulties with is the idea of that long lobe projecting soith-westwards, where there should have been a calving bay.  I have not seen anything convincing in the literature to show that the ice that pushed further south than the Isles of Scilly was genuinely grounded.  The glacial deposits in that area are more probably dumped from glacier ice floating free, beyond a calving ice edge.  In other words, they are glacio-marine deposits with dropstones, rather than deposits of true glacial till.  we look forward to seeing further info on this from the Britice-Chrono team.

==============

Britice-Chrono

Transect 4 – Irish Sea West

http://www.britice-chrono.org/transect-4-irish-sea-west/

Team:  James Scourse (leader), Colm O'Cofaigh, Danny McCarroll, Geoff Duller, Dave Evans, Siwan Davies, L Yorke, Matt Burke, Katrien Van Landeghem, G Thomas

The Irish Sea Ice Stream (ISIS), the largest drainage conduit for the MIS2 British-Irish Ice Sheet  (BIIS; Fig. 1), was fed by ice flowing southwards from southern Scotland, northern Ireland and the English Lake District. It divided around the uplands of North Wales into two discrete sectors, the EIS flowing into the Cheshire-Shropshire lowlands and the western ISIS (here denoted as WIS) flowing southwards through the central Irish Sea and into the Celtic Sea. Glaciers emanating radially from the Welsh Ice Cap contributed to WIS north and west of of Wales, and from the Wicklow Mountains on the eastern side of the Irish Sea. On entering the Celtic Sea through the topographic constraint of St George’s Channel, WIS ice extended westwards along the south coast of Ireland west of Cork and southwards as far as the Isles of Scilly. WIS was grounded 100 km SW of Scilly where a palaeo-grounding line marks an LGM transition to a marine margin. Glacimarine sediments are found on the continental shelf south and west of this position.

Current understanding

The WIS is the best dated sector of the BIIS, but this database is populated entirely from 14C, OSL and cosmogenic data from onshore samples. The age and maximum southern limit of the WIS has been established in a series of papers, both onshore in the Isles of Scilly (Scourse, 1991; Hiemstra et al., 2006; McCarroll et al., 2010) and offshore (Scourse et al., 1990; Scourse & Furze, 2001) and correlated with the deep-sea IRD record (Scourse et al., 2000, 2009a;  Haapaniemi et al., 2010).

Timing and extent of WIS advance along the south coast of Ireland has been established by O’Cofaigh & Evans (2007). Reworking of proximal glacial and glacimarine sediments by strong tidal currents along the ice margin into tidal sand ridges has been established (Scourse et al., 2009b); this reworking has had the effect of removing or masking much of the glacial sedimentary record across the Celtic shelf. The BGS has an extensive archive of core material and seismic data from across the shelf but much of this remains uninvestigated, particularly in the northern Celtic Sea including the Celtic Deep Basin.

There are significant uncertainties in our understanding of the dynamics of the WIS. Whilst ice streaming has been assumed (e.g. Stokes & Clark, 2001; Roberts et al., 2007; Chiverrell et al. in prep.) an alternative hypothesis is that a piedmont lobe extended south of Ireland, driving ice southeastwards towards Scilly. Ice-flow indicators on Scilly and Lundy (Rolfe et al., 2011) suggest ice flow from the NW.

The eastern margin of the LGM WIS south of Wales is very uncertain. Lundy was overridden by LGM ice (Rolfe et al., 2011) and it is possible that the Fremington Till of North Devon represents a  glacilacustrine sequence of LGM age deposited in a lake body dammed by offshore ice. There is no convincing evidence that the WIS impinged on the north coast of Devon or Cornwall anywhere between Fremington and Scilly.

Recent compilation and Bayesian analysis of the WIS geochronological database constrains the advance and retreat phases of WIS (Chiverrell et al. in prep.), demonstrating rapid advance and collapse of this sector of the ice sheet (Fig. 2). This analysis, the first to be applied to glacial landsystems, identifies a prior sequence based on landform/sediment relationships to reduce uncertainty in the probability distribution for individual dates. This can be used as a model for the analysis of other sectors of the BIIS.