THE BOOK
Some of the ideas discussed in this blog are published in my book called "The Bluestone Enigma" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click
HERE

Friday, 30 May 2014

An undiscovered ring cairn near Gernos Fach?



A friend who frequently wanders in the wilderness in these parts has drawn my attention to an unrecorded feature not far from Gernos Fach, on the flank of Banc Du  --  grid ref SN 077 345.  We can see it faintly on the satellite image above, not far from a little pond.

She says that just now the feature is even more prominent to the naked eye, even from ground level.

If you look carefully you can see a faint change in the vegetation, bringing out a distinct circle of green in an area dominated by moorland vegetation.  It's to the SE of the pond, right in the centre of the photo.  There are lots of modern tracks criss-crossing this area, but this "feature" looks rather different from anything else on this moorland.  So -- might it be a ring cairn like the others on Carningli and Dinas Mountain?

Note that this is less than one km from the Waun Mawn standing stones which were investigated by MPP's team a couple of years ago, in the hope that there might be some remains of a gigantic stone circle there.  I gather that particular hypothesis has gone by the board, since the stones which still remain standing and fallen cannot be fitted onto the circumference of any circle, large or small........

But thinking of man-made features, the summit of Cnwc yr Hydd (just to the north of the main standing stones) is rather interesting, since it is distinguished by a string of small quarries (at least twenty pits) which I find rather mysterious.  They don't seem to be places where large stones can have been quarried, since as far as we can see the bedrock is friable shale and mudstone, partly metamorphosed -- the altered sediments that exist right across this area between the exposures of dolerite and rhyolite belonging to the Fishguard Volcanic series.  More investigations are needed...... there is a chance that the quarries are modern, having been used for roadstone for the Gernos Fach farm track. Click to enlarge the image.


Thursday, 29 May 2014

Annual layers

I found this great photo of the annual layers in a snowpatch near a glacier edge in Iceland.  If you try, you can count these in exactly the same way as you count varves or tree rings to assess age.  The dark lines represent the melting or ablation surfaces at the end of each summer, when there is always a lot of dust and other debris on the snow or ice surface.

In Iceland, things can get complicated because of the proximity of volcanoes and the likelihood that in some years layers of ash will fall onto snow and ice surfaces.  If the ash layer is thin, it will absorb heat and accelerate melting; but if it is thick it can act as a protective layer and inhibit melting on the surface.  If the distribution of ash on a cold surface is patchy -- affected by wind turbulence, for example -- then serious complications might set in, because in some places older layers might be ablated away entirely, while in other areas they will be preserved.  So when it comes to interpretations, care is of the essence........

These layers are often transformed into ogives in glacier ice -- sometimes very much distorted by the complexities of ice flow around obstacles.

Wednesday, 28 May 2014

Callanish -- quarried slabs or erratics?


This is Colin Richards's Fig 8, showing a collapsed monolith within the Callanish X circle at Na Dromannan.  Like many of the other stones in these circles, they could not be set into sockets because the soil was thin and the circle builders simply had to set them on end, resting on bedrock and propped up with "packing stones" around their bases.  No wonder many of the stones have collapsed.......

I'm off to Lewis next week -- very exciting, since I have never had the chance before to visit the Callanish circles.  I'm with a group of old college friends, so there will be much feasting and jollification and not much time for serious fieldwork.  But I look forward to taking a look at the famous monuments......

Here is an extract from a longer paper published by Colin Richards in 2004:

Lewis

(Extract from a longer article.  See the illustrations in the original)

http://www.orkneyjar.com/archaeology/dhl/papers/cr/index.html

Rethinking the great stone circles of Northwest Britain (2004)

by Colin Richards

Possibly the most famous group of stone circles in Northern Britain, the Callanish complex, lies on the west coast of Lewis and comprises at least five stone circles with another possible example to be confirmed (Callanish XI).

A preliminary examination of the different circles in September 2002 revealed the stones to have been quarried (as opposed to glacial erratics) and to be composed of different types of Lewisian gneiss.

Figure 5. View of Callanish (I), Lewis, looking along the ridge and up the avenue

As with Orkney there seemed to be a mixture of different types of Gneiss present within each circle (Fig. 5).

However, the main circle (Callanish I), renowned for both its long avenue and projecting lines of monoliths, differed slightly in that it did comprise numerous stones with black hornblende 'eye' inclusions (which could be interpreted as a form of rock art or decoration, albeit naturally derived) (Fig. 6).

These distinctive stones were almost certainly obtained from a single outcrop and so far the only identified outcrop containing hornblende inclusions is the natural 'knoll' at the end of the ridge upon which the circle and avenue lies.

Examination of the monoliths comprising the other three circles provides a less consistent pattern with the presence of gneiss, some of which appears to be derived from a variety of different sources.

Figure 6. The black hornblende 'eye' inclusions in the stones forming part of Callanish I. These could be interpreted as constituting a form of megalithic art.

So at Callanish we immediately see a difference with Orkney in that there are more smaller circles which although incorporating different types of gneiss show a tendency to a predominance of one particular type - probably obtained from the same outcrop and place.

In 2002 a four day period of survey was undertaken with Joffy Hill to locate possible quarry sites for the circles. In particular, attention was given to a supposed quarry and 'ruined' stone circle (Callanish X) at Na Dromannan; a ridge on high ground to the north of the Callanish circles.

The 'ruined' stone circle was represented by a number of angled stones projecting through the peat at the southern end of a long ridge. The supposed quarry was a revealed rock cliff forming the western side of the ridge.

Close examination of the rock revealed in the cliff indicated it not being a source for monoliths composing the four definite Callanish circles in that the Gneiss was of different colour and grain size.

After initial inspection of the 'ruined circle' there remained a possibility that the angled stones projecting through the peat were actually stones propped up for removal after being quarried from outcropping on the spine and southern end of the ridge. Also a monolith designated as a 'standing stone' lying on a parallel ridge, 150 metres east of Na Dromannan, was clearly a monolith wedged on its side; presumably for future transportation that never occurred (Fig. 7).

Figure 7. The monolith wedged on its side for later removal.

To investigate these possibilities excavations at Na Dromannan were undertaken over a four week period during late summer in 2003.

When the peat was removed it immediately became clear that the reason for the tilt of the recumbent monoliths was that each stone rested on the slope of a pile of large packing-stones which resembled small cairns.

While some stone blocks were clearly displaced others resembled the packing stones commonly seen surrounding the bases of standing monoliths; supporting and stabilizing the standing stones within their sockets (Fig. 8).

The interpretation that the stones had all originally stood upright was quickly confirmed when a number of broken upper sections of the monoliths were revealed beneath the peat. Clearly, these had snapped when the stones had fallen onto the hard bedrock.

Figure 8. Excavating collapsed stone 15 within Na Dromannan stone circle (Callanish X).

The hardness of that bedrock appears to have prohibited deep sockets being excavated and consequently the base of each stone rested upon the exposed rock, being supported by a group of boulders packed around its base.

This raised the intriguing question of why the circle had been positioned on the rock surface; as this had caused the instability which led to eventual collapse.

The answer to this question is difficult to resolve but two features of the circle perhaps hold the key. First, Na Dromannan stone circle                was situated on the hillside overlooking the Callanish circles and when viewed from below it appears on the immediate skyline to the east.

Consequently, it was positioned in a highly visible - almost dramatic location. Although on higher ground the circle is positioned at the southern end of the narrow ridge running north-south. The ridge is formed by a combination of rock outcropping and peat of a variable depth filling in the declivities between the projecting rock.

Morphologically, the ridge is extremely similar to the those upon which the lower stone circles are positioned, particularly Callanish I, II and III, where each circle assumes an intermediate position in relation to a large glacial knoll at the end of the ridge.

Hence, in terms of topographic position, the fallen stones at Na Dromannan corresponded to the other Callanish stone circles.

The second point is that the outcropping rock at Na Dromannan appears to have been exploited as a quarry for monoliths.

As was a similar ridge approximately 100m to the east where the single monolith remained propped up (Fig 7). Here then we have the quarry site itself marked by the presence of a stone circle which again indicates the significance and special qualities attached to this place.

The evidence from Callanish paints a different picture to that seen at Stenness and Brodgar in Orkney. A large proportion of the monoliths comprising the main Callanish circle and avenue appear to have been derived from outcropping on the ridge upon which it lies.

A similar situation appears to occur at Na Dromannan stone circle. The three remaining circles seem to be more variable in composition, however, these require further investigation.

Figure 9. View of Callanish III showing the position of the circle on a ridge with the large natural knoll at its end.

In Lewis it seems as if the actual location of each circle is paramount in its understanding. In being positioned at an intermediate point along a narrow ridge, with a large natural knoll at the end, each circle constitutes an 'in-between' or transitional point within a pathway leading to the knoll (Fig. 9).

This passage along the spine of the ridge is formalised within the main Callanish circle by the presence of an impressive avenue (Fig. 5). Under these circumstances it is the natural knoll that provides the main focus of attention and to which the monumentality will constantly be referenced.

Moreover, the stone source for the majority of monoliths within the ring appears to be derived from the knoll itself (Callanish I) or outcropping on the ridge (Na Dromannan - Callanish X).

Here the possible 'sacred' nature of the stone and the 'place' may well be determining the composition and location of each circle.

The presence of monoliths within each circle from other stone sources suggests a further component of complexity which again may relate to the drawing together of different places, people and identities.

As opposed to Orkney where massive monoliths are dragged many miles from different sources to compose the circle, in Lewis people may be coming from a distance and gradually constructing different circles. However, they may be dragging and including stones from distant sources to compliment the monoliths quarried from the place of the circle.

Monday, 26 May 2014

Braided rivers in Iceland


I came across these amazing photos of braided stream patterns near the south coast of Iceland.  Absolutely beautiful -- this is where I found them:
http://www.photoguides.net/11-surreal-aerial-photographs-of-iceland

Photographer -- Andre Ermolaev.

These features are among the most ephemeral in the world of glacial geomorphology.  Quite literally, they change by the minute, so there is no real point in trying to map the stream courses.  By the time you get your map finished, the patterns are quite different.....

Tuesday, 20 May 2014

Hall Bredning: tricks of the light


Two of my all-time favourite photos -- from Hall Bredning, in the inner reaches of Scoresby Sund, East Greenland.  The subtlety of the light here is amazing, and whoever the photographer was, he was smart enough to seize the moment.......  I suspect the pics were taken within a few minutes of each other.

Outlet glacier troughs -- now and then


The spectacular image at the top is one which was recently published, showing part of the Antarctic Peninsula.  It's a bit confusing because the black area in the middle, with an irregular outline, is not water as you might think, but the ice cap that runs along the spine of the peninsula.  So here we have the highest part of the landscape, with large glaciers draining away from it towards the sea on both sides of the peninsula.  You can see the calving snouts quite clearly, at the coastline. 

The most interesting thing about the glacial troughs, filled with streaming ice, is that they are very wide, with short stumpy "feeder troughs" carrying ice down from the ice cap, but with very few tributary glaciers feeding into them  in their middle and lower sections.  This means that the main troughs have been carrying so much ice that they have effectively chopped off or truncated any tributary valleys that might have existed in this landscape prior to the arrival of the ice.

As soon as I saw this image I thought of Iceland, where there are very similar troughs, especially in the area to the west of Akureyri.  That's the area shown in the lower photo, flipped through 90 degrees so that the comparison is a bit easier to appreciate.  Now of course these valleys are all green and ice-free, although some snowfields and small glaciers still exist on the plateau that once supported an independent ice cap.  Parts of this area are also quite mountainous.

These photos illustrate what happens when you get very heavy ice discharge from the highest source areas but not many supplements afterwards -- so that the erosive capacity of the long glacier is enormous, enabling it to chop off spurs and divides as it grinds its way towards the sea.

Reminder -- no Anonymous posts

In case anybody is attempting to post comments under the "Anonymous" label, please bear in mind that all such posts go straight into the trash bin, without me even seeing them.......... most of these posts are spam, sent by some automated and randomised system, but the computer can't tell which posts are valid and which are spam.  So if you want to say something, please at least be honest enough to give your name...  Thanks!

Fresh spotted dolerite


Thanks to Chris for sending this photo.  He says this lump of spotted dolerite is near Carn Menyn (Carn Meini) and about 150m downslope from where the river springs.  Presumably that means somewhere near the "stone river" that some people get so excited about.........

It would also be not too far from the strange little burial mound that Profs TD and GW excavated a while ago, with our old friend Alice paddling about in the pouring rain.  Remember that?  It was all on the telly.......

The apparent freshness of the flanks of this stone is certainly intriguing.  Some of the heavily weathered surfaces on and near Carn Meini have of course been exposed to cosmic radiation and chemical weathering for hundreds of thousands of years,  and some which have been exposed just since the Devensian will certainly look much fresher.   This stone is worth investigating.

In this area we must be careful, because we know that local farmers (and the faithful congregation of the Mynachlogddu Chapel) have been collecting building stone from here over the past 200 years, so the stone may have been bashed about at some stage in the 1800s or even 1900s.

Monday, 19 May 2014

The wonders of weathering


I came across this the other day -- an erratic boulder in a field near here, broken during the process of field clearance with a large hydraulic digger.  Click to enlarge.

The weathered layer penetrates several centimetres in towards the core the boulder -- first a "skin" of foxy red rock altered by oxidation -- a process that needs both oxygen and acidic rainwater or groundwater.  Then there is a whitish layer which is even thicker -- I must be honest and say that I'm not sure what process is responsible for that, except to say that it will be a chemical process of some sort.  Then the unaltered rock is at the core of the boulder -- I think it's a fine-grained grey dolerite, but the wavy "micro-terrain" on the boulder surface makes me a bit unsure of that diagnosis!

Note that the weathering penetrated deeper on the angles or sharp edges of the boulder, as yopu would expect since chemical penetration is coming from two directions on those corners.

This sort of weathering only occurs when a boulder is exposed at the ground surface, and this one must have been exposed to chemical weathering attack from all sides -- if one of these faces had been embedded into the ground there would be less weathering on that face.

This gives us one reason why cosmogenic dating is so difficult.  Imagine a boulder like this being picked up and transported by a glacier, with some parts of it being eroded away during transport.  You would then get a false age from your sample, since it would have an "inherited" age different from the apparent age found on other faces of the same rock.


Friday, 16 May 2014

New erratics exposed at Traeth Mawr, Newport


There are some amazing exposures of cobbles and boulders along the foreshore at Traeth Mawr at the moment, following the winter storms and the removal of the front edge of the sand dunes.  The dunes had previously covered these exposures, which are all within 100m or so of the Surf Lifesaving Clubhouse.

What we can see at the moment is not a raised beach or storm beach exposure, since the cobbles are not rounded enough for that.  My instinct is that this is a "lag deposit" derived from Devensian till, with all the fine material washed away by wave action around the time when the sea reached more or less its present position on the coastline.  This "wave washing" process may not have lasted very long (maybe less than a century) before the sand dunes advanced seawards and covered the deposit over.

There is plenty of Devensian till in the area -- sometimes exposed on the beach itself, when the sand level is rather low (as it has been this winter) and frequently exposed within the estuary, on the north side near the Golf Course.  There are some very strange boulders embedded in the till between the tide marks -- I have previously posted pics of these.

So where have these erratics come from?  Not from Pembrokeshire, that's for sure.  The biggest stone in the top photo is Carboniferous Limestone, full of fossils.  Some of the others appear to be volcanics with interesting colours and textures.  There are some buff and grey banded sandstones and gritstones.  And in the bottom photo we see red marls and purple sandstones -- some appear very similar to the Cambrian sediments of the St David's area, and some look like the red sandstones of the ORS series in South Pembrokeshire.  But they cannot have come from either S Pembs or the St David's area, because all the evidence of ice directions is against this -- so my guess is that these rocks have come from Anglesey, the Lleyn Peninsula and the Lake District.  We should not be surprised by that -- there are pebbles of Ailsa Craig microgranite all over the place on North Pembrokeshire beaches. 

Thursday, 15 May 2014

Perched blocks -- who needs sculptors?



I did a post the other day about the fine sculpture in Kensington Gardens, London -- well, more of a boulder placement than a sculpture, much discussed with due reverence for the intentions of the sculptors and the nature of the setting.  The sculptors admitted that they were trying to mimic nature, having been inspired by seeing perched erratics in Norway.

So, feast your eyes on some other works of nature -- many locations and many origins.

Hampi, India

One of the perched Norber erratics in Yorkshire

One of the castle kopjes of South Africa

Perched erratic boulder, Newfoundland

Perched boulder, New South Wales, Australia

The Devil's Doorway in Wisconsin

Rocklands, South Africa, where huge boulders are used by the mad free-climbing fraternity for their exploits

Boulders on soft sediment pillars, New Mexico, United States

Lego man castle kopje, South Africa

Castle Kopje, South Africa

Perched erratic block, North Salem, New York State, USA

Dragon's Head, Phu Phrabat, NE Thailand

The biggest of the perched erratic blocks, Phu Phrabat, NE Thailand

Another perched erratic block, Phu Phrabat, NE Thailand













Wednesday, 14 May 2014

EH and the obsession with certainty


I got this message from a friend who has just visited the new Stonehenge Visitor Centre:

"I was at Stonehenge today and they did have your books for sale at the new shop but the exhibition is still sticking to the Wainwright / Darvill / Parker Pearson theory with no ifs or buts -- just presented as fact, not even "some geologists think...." 
 Very weak exhibition actually with all the hype and the new space I thought they could have done better."

This is all rather depressing.  I've been hesitant to comment on the content of the new exhibition until I have seen it for myself, but I now have a number of messages from visitors who cannot understand why EH apparently only deals with certainty -- ie the certainty which certain senior archaeologists have manufactured on its behalf.  For a start, it's rather disrespectful to those geologists and geomorphologists who have, over the years, argued forcefully that there was glacial involvement in the transport of stones; and secondly, it seems pretty arrogant to me that EH assumes that Joe Public cannot cope with scientific uncertainty, or with having alternative interpretations of something which is -- let's face it -- still a complete enigma.

Bluestones - "possible" sources in Wales


 Carn Goedog -- now favoured as the most likely source of most of the dolerite 
orthstats at Stonehenge

 This is a nice summary (from STONECHAT magazine) of the recent geological work.  Note the use of the word "possible" by the geologists -- it would be nice if that word was used rather more often by the archaeologists too......

Richard Bevins, Rob Ixer and Nick Pearce:
Three recent papers linking the petrology of Stonehenge Bluestones to possible sources in SW Wales.
http://implementpetrology.org/wp-content/uploads/2014/04/2014-03-stonechat.pdf
STONECHAT 1: March 2014

Two recent papers by Dr Rob Ixer (Institute of Archaeology UCL) and Dr Richard Bevins (Amgueddfa Cymru, National Museum Wales) and Professor Nick Pearce (University of Aberystwyth) were tabled for information and discussion at the 18th IPG Meeting, York 11-12 Jan 2014). The papers reported the results of their investigations into the geographical provenance for the bluestones of Stonehenge and the meaning –if any- of the debris/debitage that is associated with the Stonehenge Landscape. Their earlier papers (2010-2013) had concentrated on describing and determining the origin of the silica-rich (rhyolitic) bluestones and their debris. This work contributed to the discovery of a possible quarry source at Craig Rhosyfelin.

In their first paper (Bevins, Ixer & Pearce: 2013), focus on the spotted dolerites, considered to be the most abundant of the bluestones. Using ‘total petrography’ (a methodology synonymous with Rob, which consists of the full petrographical description of a rock in both transmitted and reflected light), Ixer and an Open University team first examined these rocks in the mid-1990s. More recently however, Bevins, Ixer and Pearce examined the rocks using a more robust methodology achieved by combining petrography and whole rock geochemistry; they concentrated on the compatible elements
which, they believed, provided a clearer discrimination between sets of samples from Stonehenge and the Preseli and revealed hitherto undetected geochemical groupings. They concluded that although there are at least two geographical sources in the Preseli Hills and perhaps more, Carn Goedog is the source of the numerically largest group of dolerite orthostats, and is the likely major source of Stonehenge doleritic bluestones. Their evidence, based on compatible element geochemistry and Principal Component Analysis, reused the Open University’s geochemical data, earlier petrographical analyses and their own previously unpublished data. To date, they have been unable to match any of the Stonehenge bluestones to the spotted dolerite bluestone quarry site at the Preseli Hills.

In the second paper (Ixer and Bevins: 11-22 ), the focus is on the relative position of the standing stones and their debris within Stonehenge and its immediate environs. It is the first paper to discuss in any detail the bluestone debitage material and to try to relate its distribution to the standing, lying and buried orthostats. For the non-dolerite lithologies there appears to be an antipathetic relationship between the debitage and the surviving orthostats. They predict that attributing the spotted dolerite debris to a named orthostat may be difficult as many dolerite orthostats cannot be distinguished from each other by either petrographical or geochemical means.

An interesting finding was that the Rhyolite Groups A-C (rhyolite with fabric) debitage, identified by Ixer and Bevins as coming from Craig Rhosyfelin, appears not to be associated with any above-ground orthostat but may be from buried orthostat SH32d or SH32e. This debitage is common in secure and non-secure prehistoric contexts. Work on the spotted dolerites including the paper above suggest that other bluestone lithologies have yet to be identified and fully described.

REFERENCES

Bevins, R.E, Pearce, N.J.P, and Ixer, R.A Pearce (2011) Stonehenge rhyolitic bluestone sources and the application of zircon chemistry as a new tool for provenancing rhyolitic lithics. Journal of Archaeological Sciences, 38, 605-622.

Ixer, R.A, Williams-Thorpe, O, Bevins, R.E, and Chambers, A.D (2004) A comparison between ‘total petrography’ and geochemistry using portable X-ray fluorescence as provenancing tools for some Midlands axe-heads; in E.A Walker, F. Wenban-Smith and F. Healy (eds), Lithics in Action. 105-115: Oxford; Oxbow/Lithics Studies Society Occasional Publication 8.

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 E.R (2011) The detailed petrography of six orthostats from the bluestone circle, Stonehenge; in Wiltshire Archaeological & Natural History Magazine 104, 1-14.

Ixer, R.A and Bevins, E.R (2013) Craig Rhos-y-Felin, Pont Saeson is the dominant source of the Stonehange rhyolitic ‘debitage’; in Archaeology in Wales 50, 21-31

Ixer, R.A and Bevins, R.E (2013) Chips off the old block: the Stonehenge debitage dilemma. Archaeology in Wales 52, 11-22.

Saturday, 10 May 2014

CAPTCHA gone -- Anon posts going too



Now that I have dumped CAPTCHA, more automated spam messages (called bots?) are indeed coming through to me -- so I shall set up a filter on my mail programme to ensure that anything sent by "Anonymous" goes straight into the Trash and is not even seen by me on my incoming mail list.

So a plea -- all future messages should have proper names (or pseudonyms, if you are of a retiring disposition)  in the appropriate box.  Otherwise they will just disappear into the ether -- or the E-cloud, or wherever unwanted things go to die.........

Friday, 9 May 2014

CAPCHA gone.....

Thanks to Pete G for warning me about the irritation involved in getting through this wretched "word verification" thing called CAPCHA.  It probably discourages lots of people from commenting.

I think I have now managed to turn it off..... would somebody please now confirm this for me?

Many thanks

Brian

Wednesday, 7 May 2014

The Stones of Stonehenge Project


 Stones, and more stones.  
One of Pete Glastonbury's fine photos -- the bluestone with a groove.......

Here are a few interesting titbits.  They inform us that the Stones of Stonehenge project (which will be conducting digs this year at Clatford Bottom, Rhosyfelin and Castell Mawr) is funded by the National Geographic Soc, Royal Archaeological Institute and the Society of Antiquaries -- although there is no indication of the scale of the funding.  I hadn't realised that Austen and Schlee are involved as the "local experts"............ I wonder if they know anything about geomorphology?

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

Royal Archaeological Institute
http://www.royalarchinst.org/grants

Recent Grants


Research grants for 2014 have been awarded to the following:

    • Murray Cook and Fraser Hunter: Strathdon Material Culture Review
    • Elizabeth Foulds: New light on old sites: Investigations into the settlement at Swallowcliffe Down, Wiltshire
    • Dr Peter Halkon and Rodney Mackey: Trial excavation on a major new multi-period site near Melton, East Yorkshire
    • Derek Hurst: New light on the archive of the 1935–7 excavation of Kemerton Camp, Bredon Hill, Worcestershire
    • Professor Mike Parker Pearson: Preseli Stones of Stonehenge
    • Dr David Petts and Dr Chris Whitmore: Binchester Research Project: Vicus Bath-house
One of the conditions attached to the awarding of a grant is that the recipient must produce a report of the work undertaken. A shortened version of the report is published in the RAI Newsletter.

===========

The Stones of Stonehenge

http://www.ucl.ac.uk/archaeology/research/directory/stones-of-stonehenge-parkerpearson

The Stonehenge Riverside Project, which undertook major excavations at the henge monument of Durrington Walls and elsewhere in the Stonehenge World Heritage site between 2004 and 2009, has led to further research to explore the origin of the stones used to build Stonehenge itself.

Survey and excavation is taking place in north Wiltshire, to trace the source of the sarsens, and in west Wales, the point of origin of the smaller bluestones. The project brings together many of the Stonehenge Riverside Project team members and associates (Pollard, Richards, Welham, Pike) and draws on the expertise of other researchers working on the archaeology of the Marlborough downs (Gittings, Allen, French) and in west Wales (Austen, Schlee).

Geological analysis by project partners Bevins and Ixer has pinpointed the precise source of one of the Stonehenge bluestones.  Research on the Stones of Stonehenge project continued in 2013 in both Wiltshire and Wales.

    • Read more about the geological analysis here»
Related outputs

    • Parker Pearson, M.2012. Stonehenge: exploring the greatest Stone Age mystery. London: Simon & Schuster.

    • French, C., Scaife, R. and Allen, M.J. with Parker Pearson, M., Pollard, J., Richards, C., Thomas, J., Welham, K. 2012. Durrington Walls to West Amesbury by way of Stonehenge: a major transformation of the Holocene landscape. Antiquaries Journal 92: 1-36.

    • Parker Pearson, M.2012. Stonehenge and the beginning of the British Neolithic. In A.M. Jones, C.J. Pollard, M.J. Allen and J. Gardiner (eds) Image, Memory and Monumentality: archaeological engagements with the material world. Prehistoric Society Research Paper No. 5. Oxford: Oxbow. 18-28.

    • Parker Pearson, M., Pollard, J., Richards, C., Thomas, J., Welham, K., Bevins, R., Ixer, R., Marshall, P and Chamberlain, A. 2011. Stonehenge: controversies of the bluestones. In L. García Sanjuán, C. Scarre and D.W. Wheatley (eds) Exploring Time and Matter in Prehistoric Monuments. Menga: Journal of Andalusian Prehistory, Monograph no. 1. Seville: Junta de Andalucía. 219-50.
Funding

    • National Geographic Society
    • Royal Archaeological Institute
    • Society of Antiquaries

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

Stonehenge bluestone mystery revealed


28 November 2013
http://www.ucl.ac.uk/archaeology/calendar/articles/2013-14/20131128


The exact origin of the Stonehenge bluestones appears to have been revealed according to newly-published research by Rob Ixer (Honorary Senior Research Associate at the Institute) and colleagues.

Two recent papers by Drs Rob Ixer (UCL Institute of Archaeology), Richard Bevins (Amgueddfa Cymru, National Museum Wales) and Prof Nick Pearce (University of Aberystwyth) continue their investigations into the geographical provenance for the bluestones of Stonehenge and the meaning, if any, of the debris/debitage that is found throughout the Stonehenge Landscape.

The article entitled 'Carn Goedog is the likely major source of Stonehenge doleritic bluestones: evidence based on compatible element geochemistry and Principal Component Analysis' which has recently been published in the Journal of Archaeological Science suggests that although there are at least two geographical sources in the Preseli Hills and perhaps more, Carn Goedog is the source of the numerically largest group of dolerite orthostats. Carn Menyn, for a long time the favourite site for the spotted dolerite bluestone quarry, was found not to be a match for any of the Stonehenge bluestones.

According to Dr Rob Ixer:

    • “This initial step in the quest to determine the origins of the doleritic bluestone shows that the commonly held beliefs about their source(s) are incorrect and suggests that new, dedicated collecting of the Preseli Hills outcrops especially on their northern slopes together with a reanalysis of the Stonehenge orthostats could well ‘solve’ the mystery of who/what moved the stones and from where”.

The second paper entitled 'Chips off the old block: the Stonehenge debitage dilemma' published in Archaeology in Wales, discusses the relative position of the standing stones and their debris within Stonehenge and its immediate environs. It is the first paper to discuss in any detail the loose lithic bluestone material and to try to relate the distribution of this abundant material to the standing/lying and buried orthostats.

Debris from the Altar Stone and orthostats Stonehenge 48 and 38 (all above ground) have been recognised and found to be numerically very rare but widely distributed throughout the Stonehenge Landscape and not just close to their parent stone. However as most of the occurrences are in late and disturbed archaeological contexts it is not possible to say when they were separated, but they are very rare in prehistoric contexts.

As Rob indicates:

    • “The scattered debris/debitage within the Stonehenge Landscape has everything to tell us about the history of the stones once they reached Stonehenge. Careful plotting their distribution in time and space begins to narrate this story.”

References

    • Bevins, RE, Ixer, RA and NJG Pearce. 2013. Carn Goedog is the likely major source of Stonehenge doleritic bluestones: evidence based on compatible element geochemistry and Principal Component Analysis. Journal of Archaeological Science [available online 19 November 2013]

    • Ixer, RA and Bevins, RE. 2013. Chips off the old block: the Stonehenge debitage dilemma. Archaeology in Wales 52 11-22.

Comment from a little fringe blog.....



Have a look at this:
http://mikepitts.wordpress.com/
Quote: "When I was a student in London, learning some basic geology for my archaeology degree, we talked about Stonehenge. A geologist had just proposed that the bluestones, the small stones from Wales, had not been carried there by people, but by glaciers. It was an old idea, and one that still stirs a little fringe debate, but unusually this time the case was presented in the pages of Nature (“Glaciation and the stones of Stonehenge”, by GA Kellaway, Nature 233, 30-35, 3 September 1971)"
How condescending can you get?  Never mind -- let that pass, since we all have different priorities.   Of much greater interest than Mike's little fringe blog is his photo of a sculpture called "Rock on top of another Rock,"  by Peter Fischli and David Weiss, in Kensington Gardens in London, near the Serpentine gallery.  Apparently the rocks are made of what looks like dolerite, and they come from Wales.  Did the sculptors go to Wales to collect them?  And if so, where did they go, and why?

Stunning images from Novaya Zemlya


I've always been attracted by Novaya Zemlya  -- two huge and very mysterious islands in the Arctic. off the coast of Russia, with a vast expanse of glaciated terrain and very active glaciers.  Because this was a nuclear testing zone in the Cold war, and because there are still sensitive military installations in secret locations, we have not seen many images of the islands in the past.  But with the advent of satellite photography nothing much can be kept secret, and these images have appeared on the web, along with many others.

Monday, 5 May 2014

The myth of the straight ice edge


It's interesting that in the specialist literature we still see maps showing long straight ice edges -- like the one above, in a paper by Etienne et al in 2006.  Given that this is to some extent a scale issue, with minor crenellations in the ice edge "evened out" for ease of interpretation, it is also unfortunate in that some readers might get a very simplistic view of how ice edges behave.  In general, an ice edge like that shown in the map would only exist where very special conditions exist on the ground -- for example on an plateau surface or on a low-level plain virtually devoid of prominent surface features.  Here is one example from the Greenland Ice Sheet near Cape Alexander:


Much more commonly we find this sort of thing:




The upper two photos are oblique aerial photos and the lower one is a satellite image from Google Earth -- all three images are from Greenland.  What we see are ice edges that are very complex indeed, with ice tongues pushing into all low-lying areas and with higher ground / hill masses standing proud of the ice as enclaves or nunataks or as elongated "peninsulas".  Lakes are impounded against rising ground, but the picture portrayed in the map at the top of this photo would have been almost impossible in the real world.

In the real world of West Wales, as I have said before,  the Devensian ice edge of the Irish Sea Glacier must have been somewhat on the lines of the maps below:



Bearing in mind that the coast was not in its present position at the time, and that most of Cardigan Bay and St George's Channel was dry land, the key determinants of ice edge position (apart from the glaciological ones) would have been the uplands of Preseli and Carningli - Dinas Mountain and -- at a lower level -- the old cliffline of North Pembrokeshire,  presenting a rampart which was in some places more than 100m high.  The ice managed to surmount this old cliffline along the full length of the North Pembrokeshire coast, but in St Bride's Bay and around the Dale Peninsula the ice was not sufficiently thick or powerful to surmount the obstacle and press far inland.  So from Newgale southwards all of the Devensian glacial and fluvioglacial deposits are plastered along the coastline, or at the most a kilometre or so inland.  The ice must have pushed some way into Milford Haven, for there are ice contact deposits at West Angle Bay.

South of Milford Haven the question of whether Devensian ice actually passed across the limestone plateau of Castlemartin is still to be resolved.  But I'm pretty sure that the ice pressed eastwards along this coastline, maybe with the glacier flank pressed against the limestone cliffs, at least as far east as Caldey Island.  The fresh till in Ballum's Bay, which is uncemented and which contains ORS cobbles and larger erratics, must have been laid down by ice travelling from west towards the east.

http://brian-mountainman.blogspot.co.uk/2011/08/devensian-till-at-bullums-bay-caldey.html

The only glaciological scenario which makes sense here is one involving ice travelling ACROSS St George's Channel, and not along it, as shown on the (hypothetical) map of the Celtic Sea Piedmont Glacier.   I am also happy with the idea that Devensian ice reached Lundy Island, the west-facing coasts of Devon and Cornwall, and the Scilly Islands.

So the map published by Clark et al (2010) in Quaternary Science Reviews just doesn't make sense to me, since ice does not flow in long thin lobes with virtually zero gradient across wide open coastal plains.......  I'm not up to speed with everything going on in British glacial geomorphology at the moment, but I trust that by now this map has been substantially revised!


So what we need in the Bristol Channel, if we are to make sense of the field evidence, is a highly crenellated ice edge, entirely in tune with what we see in analogous situations in Greenland today

Reference:
Pattern and timing of retreat of the last British-Irish Ice Sheet
Chris D. Clark, Anna L.C. Hughes, Sarah L. Greenwood , Colm Jordan , Hans Petter Sejrup
Quaternary Science Reviews(2010) pp 1-35


Latest scientific analyses?

 Might be of interest --  but don't try to go, because there are no tickets left!  I wonder whether there will be any mention of the radiocarbon dates and other sample analyses from years 2011 - 2013?

........."why some of its stones were brought from nearly 200 miles away........"   Repeat something often enough and hope that it becomes true........ not very scientific, but then this is not about science.

-------------------------------

Inaugural Lecture - Professor Mike Parker Pearson (UCL Institute of Archaeology)
UCL Joint Faculty
Tuesday, 6 May 2014 from 18:30 to 19:30 (BST)

On the Road to Stonehenge

Stonehenge is one of the greatest mysteries of world prehistory. As an architectural project, its scope has seemed beyond the capabilities of Neolithic society, leading to widespread speculation about lost civilizations and even extra-terrestrials. The last decade of archaeological research has produced a wealth of new information about this mysterious stone circle and the people who built it. The results of the latest excavations and scientific analyses are providing major insights into questions such as why Stonehenge was built and why some of its stones were brought from nearly 200 miles away.

Professor Mike Parker Pearson
UCL Institute of Archaeology

Saturday, 3 May 2014

Mauls, hammerstones and erratics


The things above are conventionally referred to as mauls, in that they are more irregular in shape than hammerstones and sometimes show evidence of grooves or gripping protrusions to assist in using them for hammering or shaping other stones or organic materials.  Some of them were primitive hammers in that they were bound to a shaft or handle -- and in some cases they were used as weapons, with quite large and heavy stones fixed to a shaft maybe more than a metre long, and used for bashing mammoths or men (if you could get close enough to them while carting around something weighing 10kg or more).  So are there any of these at Rhosyfelin?  I don't recall any mention of them thus far......


As for hammerstones, we have heard about these in MPP's lectures, but I recall seeing just one photo.  Hammerstones come in all sorts of sizes, but of course there is an upper limit to what can be handled and wielded in the process of smashing chunks off larger rocks or breaking boulders or slabs down into smaller fragments.  The illustrations above, by the way,  have nothing to do with Rhosyfelin.......

Some hammerstones -- like the one at top left and the middle stone in the group of three -- have clear evidence of fracturing or percussion marks, and one might find such marks to be good evidence of human use as tools.  But as I have said before, many rounded cobbles and stones have natural markings on them (fractures, grooves pits), and one person's natural phenomenon is another person's hammerstone.  If the presence of hammerstones at Rhosyfelin is crucial to the argument that this place was a Neolithic quarry, it will be interesting to see how strong the evidence actually is that certain stones were used for the bashing of orthostats intended for export to Stonehenge.  Where exactly did they come from in the Rhosyfelin stratigraphy, and how convincing are the percussion marks?



Then we come to the erratics, which are quite frequent at Rhosyfelin.  The top photo here shows a collection of stones taken from the excavations and dumped on the edge of the dig site.  As we can see, some of these are bits and pieces of local rhyolite, and other boulders and stones are rounded or sub-angular in shape, some so big that they can just about be handled by one man -- but certainly too big to be used as either a weapon or a tool......  Mostly these seem to be made of dolerite, but they need to be examined in more detail.  The photo below shows one of these stones in its natural position, embedded in the glacial deposits near the base of the sediment sequence.

It would clearly be ludicrous to suggest that these boulders are anything to do with a quarry -- but I have not yet heard any mention of them from the Rhosyfelin dig team.  Do they admit that there are glacial deposits and glacial erratics here, or have they been airbrushed out so as not to make the story too confusing?  Even more interesting -- have they been interpreted as rather large hammerstones?