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Friday, 19 January 2018

Field et al 2014: The Landscape and Earthworks



Reference:
David Field, Neil Linford, Martyn Barber, Hugo Anderson-Whymark, Mark Bowden, Peter Topping, Paul Linford, Marcus Abbott, Paul Bryan, Deborah Cunliffe, Caroline Hardie, Louise Martin, Andy Payne, Trevor Pearson, Fiona Small, Nicky Smith, Sharon Soutar and Helen Winton (2014). Analytical Surveys of Stonehenge and its Immediate Environs, 2009–2013:
Part 1 – the Landscape and Earthworks.
Proceedings of the Prehistoric Society, 80, pp 1-32 
doi:10.1017/ppr.2014.6

Quote:

The Project brought to bear an integrated array of non-invasive survey techniques, including earthwork analysis, geophysics, laser scanning, and aerial survey, together with documentary and archive research. All monuments in the World Heritage Site with a visible surface component were investigated........

This part of the paper concentrates on everything other than the stones, within and beyond the Stonehenge earthworks.  There are many interesting observations.

Figure 2 from the paper, showing the twentieth century excavated area.  It is still the case that only about 50% of the area occupied by the stone monument has been excavated.    So the stratigraphy is still only partly known, as is the nature of the Stonehenge Layer and the characteristics an origins of the stones and fragments that happen to have been collected.  If anybody says to you "Twenty percent (or whatever) of the rhyolite debitage at Stonehenge has come from the Rhosyfelin area", what they actually mean is "twenty percent of the rhyolite samples that happen to have been collected from the bits that we know something about......."

There is a short section on the "periglacial stripes" described so lovingly by MPP and his colleagues, but it's disappointing that the authors do not really examine the very dodgy use of this "periglacial" label -- and in the process perpetrate the myth.  As I have said many times before, I  see no reason to use the periglacial label myself, in spite of being rather fond of periglacial geomorphology, since the most parsimonious explanation of these "parallel stripes" is simply that they are solutional rills formed by water flowing downslope on a shallow gradient over many millennia. Field et al say "it seems most likely that they (the stripes or rills) represent a geological interface, perhaps concentrated flint or marl seams embedded within the underlying chalk."  I agree with that 100%.

As for the MPP idea that Stonehenge is where it is, and the alignment of the Avenue is what it is,  because of the alignment of these rills -- the authors are mercifully silent, suggesting to me that they don't think much of it........

 More attention is given to a little mound -- just 25 cm high, in the southern part of the stone setting.  It's about 15 m across, and has an irregular surface.   Apart from assuming that it is natural, the authors are a bit mystified by it.  Something to do with the irregular surface of the chalk?  Something to do with the Stonehenge Layer?  Something to do with solution hollows or the past location of sarsens removed and erected on the site? 

 Quote: "Several authorities have suggested that the sarsens were sourced from the area of Stonehenge or somewhere closely adjacent (see below). Darvill et al. (2012, 1029) have recently suggested that some stone was probably present on site at the outset; notably the massive cone-shaped Heelstone as it has been considered to have been extremely difficult to move (Johnson 2008, 121), an observation supported by measurements taken from the laser scan data which demonstrates that it is the heaviest stone on site (Abbott & Anderson Whymark 2012; Field et al. forthcoming). "

There is some interesting wotk on the barrowes (we won't delve into tht just now), with a suggestion that some of them may have originated as long barrows and that there may have been a number of phases of construction / modification.  Quote: "It is clear that far from being isolated, Stonehenge may have been a component part in a ceremonial and funerary area within its immediate environs, with origins and traditions potentially traceable to the earlier Neolithic.  Initially at least the focus of activities may have been around one or more of these other monuments." Interesting.......

Now to the North and South Barrows within the Stonehenge earthworks.  Yet more interesting info. The authors suggest that the North Barrow is not younger than the  rest of the monument (as normally assumed), but is probably older.  The interesting thing about this is that Atkinson recorded bluestone chips in its bank -- and if his records are correct, that must mean that bluestone fragments were present on this site BEFORE the Stonehenge embankment was constructed.  This is a highly significant finding, and I am not aware of any comments on it thus far in the recent literature.  This paper accepts that the bank and ditch were built around 5,000 yrs BP.




There is a detailed and fascinating discussion of the embankment, ditch and Avenue, and the relations between them -- very fastidious and well described, and mercifully free of speculation.  Then the authors go on to describe the barrows in the Stonehenge landscape, and the Y and Z holes.

Overall, the most interesting things to come out of this paper are:

1. The so-called periglacial stripes are not accorded any great significance, either in landscape terms or in the interpretation of the Avenue or the Stonehenge area as a whole.

2.  The authors appear to have no problem with the idea that many or most of the sarsens at Stonehenge have come from the neighbourhood.

3.  If the North Barrow is indeed older than the Stonehenge embankment, it shows that bluestone fragments were present in this landscape before work started on the Stonehenge earthworks.    That of course would support the thesis that other long barrows could contain bluestones as well -- and that the Boles Barrow bluestone was indeed embedded in the Neolithic long barrow there,  well before Stonehenge was thought about.......















Investigating the Stonehenge Triangle

The triangle investigated in this study


Many thanks to Rob for drawing these to my attention.  Somehow, we all missed them before! But these are important papers, one dated 2014 and the other 2015.  Actually, they are two parts of a single long article, with multiple authors.  The authors stress that there is no new digging here -- this research is all "non-invasive", but it's nonetheless interesting and important, adding a lot to our understanding of the triangle of land referred to as the EG "guardianship area", north of the A303 road.

I'll refer to these two papers as Field et al (2014) and Field et al (2015).

Here are the details:

David Field, Neil Linford, Martyn Barber, Hugo Anderson-Whymark, Mark Bowden, Peter Topping, Paul Linford, Marcus Abbott, Paul Bryan, Deborah Cunliffe, Caroline Hardie, Louise Martin, Andy Payne, Trevor Pearson, Fiona Small, Nicky Smith, Sharon Soutar and Helen Winton (2014). Analytical Surveys of Stonehenge and its Immediate Environs, 2009–2013: 
Part 1 – the Landscape and Earthworks.
Proceedings of the Prehistoric Society, 80, pp 1-32 
doi:10.1017/ppr.2014.6

ABSTRACT

Integrated non-invasive survey in the Stonehenge ‘triangle’, Amesbury, Wiltshire, has highlighted a number of features that have a significant bearing on the interpretation of the site. Among them are periglacial and natural topographical structures, including a chalk mound that may have influenced site development. Some geophysical anomalies are similar to the post-holes in the car park of known Mesolithic date, while others beneath the barrows to the west may point to activity contemporary with Stonehenge itself. Evidence that the ‘North Barrow’ may be earlier in the accepted sequence is presented and the difference between the eastern and western parts of the enclosure ditch highlighted, while new data relating to the Y and Z Holes and to the presence of internal banks that mirror their respective circuits is also outlined.


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

David Field, Hugo Anderson-Whymark, Neil Linford, Martyn Barber, Mark Bowden, Paul Linford, Peter Topping, , Marcus Abbott, Paul Bryan, Deborah Cunliffe, Caroline Hardie, Louise Martin, Andy Payne, Trevor Pearson, Fiona Small, Nicky Smith, Sharon Soutar and Helen Winton (2015). Analytical Surveys of Stonehenge and its Environs, 2009–2013: 
Part 2 – the Stones. 
Proceedings of the Prehistoric Society, 81, pp 125-148
doi:10.1017/ppr.2015.2


ABSTRACT

Non-invasive survey in the Stonehenge ‘Triangle’, Amesbury, Wiltshire, has highlighted a number of features that have a significant bearing on the interpretation of the site. Geophysical anomalies may signal the position of buried stones adding to the possibility of former stone arrangements, while laser scanning has provided detail on the manner in which the stones have been dressed; some subsequently carved with axe and dagger symbols. The probability that a lintelled bluestone trilithon formed an entrance in the north-east is signposted. This work has added detail that allows discussion on the question of whether the sarsen circle was a completed structure, although it is by no means conclusive in this respect. Instead, it is suggested that it was built as a façade, with other parts of the circuit added and with an entrance in the south.

I'll devote separate posts to these two articles..... watch this space.

More about Durrington Walls and animal teeth


Affinities of sampled animal remains at Durrington Walls with UK environmental / geological contexts -- source:  Current Archaeology

There's an interesting article in Current Archaeology 334, published in connection with the exhibition in the Stonehenge Visitor Centre called "Feast!  Food at Stonehenge."    It's by Hilts et al, and summarises much info already published about the feasting that went in at Durrington Walls, possibly at the time when a lot of work was going on at nearby Stonehenge, around 4,500 yrs BP.

Neolithic food miles: Feeding the builders of Stonehenge
Hilts, C., Greaney, S., Madgwick, R. and Parker Pearson, M. 2017. Neolithic Food Miles: Feeding the 'builders of Stonehenge'. Current Archaeology 334: 26-31.

The article concentrates on the animal remains, and the latest findings (from Richard Madgwick of Cardiff University) bring up to date the earlier info discussed on this blog about strontium isotopes in the teeth of cattle and pigs.   They can be matched to specific geological locations -- or more accurately, to specific rock types and environments.   Sure enough, as suggested earlier, some of the animals slaughtered and eaten in these jolly BBQs  were from far away, but the great majority (percentages are meaningless in this sort of context) were from "middle England" -- 65 of the animals probably having been raised within 50 miles of Durrington Walls.  Of those that were clearly not local, 14 pigs and 4 cattle appear to have come from the south of Cornwall, at least 180 miles away. Only 14 pigs and 4 cattle appear to have come from more distant parts, "at potential locations as far-flung as west Wales, upland northern England, and perhaps even north-east Scotland."  It is of course interesting that cattle and pigs were being driven to Durrington over distances of 200 miles or more -- but there is no justification whatsoever in the evidence presented for suggesting "west Wales" as a place where some of these cattle and pigs were raised.  (The only reason for that mention is, of course, that MPP and his colleagues are desperate to establish a connection, for reasons that are obvious........)  It's much more likely that the little group of animals that appear to have connections with the pink areas on the map came from SE Wales and the Welsh borders.

So there is nothing in this article to show that there was any sort of  "special relationship" between Salisbury Plain and Pembrokeshire -- and this of course is the conclusion we have to reach when we look at many other cultural indicators as well.  Please forget all that stuff about "political unification".......




Tuesday, 16 January 2018

Drygalski Mountains, Antarctica




Couldn't resist posting these fabulous images from Michael Martin's collection.   They are from the Drygalski Range in Antarctica -- and extraordinary set of nunataks in which massive vertical cliffs  and sharp peaks abound.

You can see the location of the lower photo in the upper one -- it's the huge vertical cliff to left of centre, with a vast snowfield beyond.  Look at the men for scale..........

POSTSCRIPT
Found another wonderful image....



Wednesday, 3 January 2018

Happy New Year!


Happy New Year to all of the jolly followers of this blog -- may it be kind to all of us as we press on with our quest for the truth!

The pic is from Blidö in the Stockholm Archipelago -- I think I took it on the shortest day of the year.   Bright sun, low pressure, VERY high water, and ice around the edges of the bay.  You can see some thin surface ice in the photo.  Ice forms in places where the water is still and when air temperatures are around -4 deg C.  The water temperature is around -2 deg C at the moment.   We had a sauna the other day, and gently subsided into the water -- it was less traumatic than might be supposed......

At present there are about 6 hours of daylight each day -- its getting lighter now by 2 mins every day. On 21st December it was pitch black at 3 pm.


Friday, 22 December 2017

More fun and games on Lundy Island


On this map from Carr, Hiemstra and Owen (2017) the "established" Late Devensian ice limit is shown with a solid line. Established by whom?  It is inaccurate in Pembrokeshire, and the dashed line showing an ice edge close to the coasts of Devon and Cornwall seems to be a much better fit for the field evidence

Here is a new paper:

Landscape evolution of Lundy Island: challenging the proposed MIS 3 glaciation of SW Britain
Simon J. Carr, John F. Hiemstra, Geraint Owenhttp://dx.doi.org/10.1016/j.pgeola.2017.06.005Proceedings of the Geologists’ Association 128 (2017) 722–741

A B S T R A C TLundy Island, in the Bristol Channel of south-west Britain, holds a pivotal place in understanding theextent and timing of Quaternary glaciations in southern Britain, in particular the timing, extent anddynamics of the Irish Sea Ice Stream during the Devensian glaciation. New geomorphologicalobservations and revised interpretations of geomorphological and cosmogenic exposure data lead tothe conclusion that Lundy was not covered by ice in the last (Devensian) glaciation. Geomorphological features are related to surface lowering by means of granite weathering under mainly periglacial and cool-temperate conditions. Previously reported cosmogenic ages are re-interpreted to reflect a dynamic equilibrium of cosmogenic nuclide production and surface lowering during a prolonged period of subaerial granite weathering. This re-evaluation of the geomorphology of Lundy Island challenges recently proposed interpretations of early glacial cover of Lundy (MIS 4-3) and for cold-based ice cover at the Last Glacial Maximum (MIS 2), and instead supports existing regional ice sheet reconstructions. This study demonstrates that a robust, coherent geomorphological framework is fundamentally important to support the validity of detailed geochronological and stratigraphic investigations

It’s always good to see an old-fashioned geomorphological row going on — conducted, as ever, in the politest possible terms. In this paper, Carr, Hiemstra and Owen go after Chris Rolfe and others who have suggested (rather uniquely, it has to be said) that the most dramatic recent glaciation of Lundy Island was during the Early Devensian, at a time when most workers consider the Bristol Channel basin to have been ice-free. We have considered the Rolfe thesis here:
https://brian-mountainman.blogspot.se/2015/03/a-lundy-island-spat.html
and you can find other discussions on Lundy by typing "Rolfe Lundy" into the search box........

I have been somewhat sceptical about the "Rolfe theory", largely on the basis that it appears to be unsupported elsewhere. My own feeling was, on reading the Rolfe et al (2012) paper, that the cosmogenic dates / exposure ages on which it depends were all inaccurate for some reason or another. Maybe the cause of the false (?) readings was intermittent rock surface cover or rock surface breakdown by weathering……… 

Anyway, when I got at this PDF I was rather interested in what the new authors had to say. The abstract is above.


I was rather concerned at the outset by the authors’ assumption that there are accepted “regional reconstructions” and “determined ice margins” for other parts of the Celtic Sea / Bristol Channel arena. They also refer to "the established regional model of glaciation of the Southwest British Isles” as if it is soundly based and widely accepted. Well, I don’t think it is, and since the LGM maximum of the Irish Sea Glacier is in the wrong place in West Wales on Figure 1, it is very probably in the wrong places elsewhere as well.

The authors give a summary of the geology and regional context of Lundy, and when they consider the borehole and sedimentary evidence from the floor of the Bristol Channel. Strangely, they are disinclined to believe the data with respect to glacigenic sediments beneath sea-level, and suggest that the deposits referred to as “glacigenic” may not actually have a glacial origin because there are no known scouring or streamlining features in the vicinity. I don’t follow that line of reasoning at all, since some glaciated areas have streamlined features and others do not. Anyway, at an early stage in the paper it’s fairly obvious where the authors are heading.

In the “evidence” part of the paper, the authors seek to systematically dismantle the claims by Rolfe et a that there are streamlined granite surfaces and associated features, whaleback forms, grooves and meltwater channels, erratic scatters and perched boulders, tors, faceted clasts and diamictons, and periglacial materials. Then they reinterpret the cosmogenic dates as corrupt because of the gradual lowering of granite surfaces by granular disintegration and “grus” production.

These are the conclusions:
An evaluation of the geomorphological evidence previously reported by Mitchell (1968) and Rolfe et al. (2012, 2014) in support of Devensian glaciation of Lundy Island cannot be reconciled with any glaciologically-plausible or coherent glacial landsystems. Re-examination of the geomorphology of Lundy Island identifies a suite of related landforms that reflect a combination of subaerial processes of pneumatolysis, granite weathering and slope movement operating under cool-maritime temperate and periglacial conditions, with more recent impact of wildfires and human agency. Critically, this study finds no evidence for past glaciation, contrary to previous work. A revised model of Late Quaternary landscape evolution of Lundy Island dominated by granite weathering periodically enhanced by periglacial conditions offers a simple and realistic explanation of previously-published cosmogenic nuclide dates. This revised model removes the need to explain an additional MIS 3/4 glacial advance not recorded elsewhere in the southwestern sector of the BIIS, and conforms to the established regional glacial stratigraphy of the Irish Sea Ice Stream, as well as previously-reported periglacial development of tors on nearby Dartmoor.
So where does this leave us? Some of the evidence presented here is convincing, and the authors are right, I think, to question some of the assumptions of Rolfe et al about what happened on Lundy in the Early and Late Devensan. But just as Rolfe et al have “forced” the evidence into their hypothesis, and have found traces of glaciation everywhere, Carr et al have gone to the other extreme, and have forced all their evidence into a non-glacial hypothesis. In particular, they seek to argue that the so-called “glacial features” described by Rolfe et al "cannot be reconciled with any glaciologically-plausible or coherent glacial land systems” — I find that unsettling, since landforms and deposits in close juxtaposition do not need to be contemporaneous or even to belong to the same “glaciological plausible” episode. Just because granite surfaces degrade and break up to create scatters of grus and even broken granite cobbles, that does not mean that the surfaces are not glaciated; and just because assorted degradational processes are at work in grooves and bedrock channels, that does not mean that they have not also been affected by glacial meltwater. Just because there are tors nearby, that does not mean that nearby surfaces cannot have been streamlined; and I have seen far too many meltwater channels adjacent to streamlined surfaces to think that the two are mutually exclusive.

The jury is still out. I remain convinced (not having been to Lundy, and having to depend on published evidence) that the island has been affected by overriding ice during the Devensian, and that there are real problems of timing or dating. The reference to an Early Devensian glaciation is anomalous, since one would expect to see evidence of it in Pembrokeshire and elsewhere. And I remain convinced that this new paper by Carr et al does nothing to confirm the correctness of "the established regional model of glaciation of the Southwest British Isles”. I still think that strange lobe of ice pushing out into the Celtic Sea does not make sense.

Monday, 18 December 2017

BRITICE is not much help on the Stonehenge front......



Thanks to Peter for drawing our attention to this post from Tim Daw.
http://www.sarsen.org/2017/11/stonehenge-glacial-transport-of.html

Tim seems to think that the glacial transport hypothesis is dead, because nothing shows up on the BRITICE map which I referred to in a recent post. Sorry Tim, but before committing yourself to print you should have read the BRITICE stuff more carefully, since it refers specifically to the Late Devensian glaciation.  It has no relevance for the Stonehenge debate.  Wrong glaciation.  Forget it.

And as for Jim Scourse's article from 1997 -- for goodness' sake, that is 20 years out of date.  Hundreds of relevant articles have been published since that was published.  The debate has moved on, and as I have shown on this blog, it is now accepted that on glaciological grounds it is perfectly possible that ice during the larger past glaciations did indeed reach Salisbury Plain. As I have said on this blog, I am not at all happy with that old article anyway.  Read my past posts.