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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.......















9 comments:

Neil Wiseman said...

Hi Brian,

1) The so-called Periglacial Stripes are caused, in my view, by the periodic melting of permafrost. They happen to align with Solstice Sunrise because that's the direction to which the grade slopes. They continue on past the Elbow.
It should also be noted that two of the runnels on the Avenue's west side are definitely wagon tracks. These sweep into the henge through the northeast causeway and continue around the west side till they merge with the original Byway-12. This is clearly seen in 2nd Lt. Phillip Sharpe's aerial pictures of 1906. I have little doubt it was a farm-to-market route used for years by vendors trading between Larkhill and Normanton. Pretty convenient shortcut!

2) I'm sure some of the Sarsens at the Pile are local, and there's no reason to assume they're not. The Heelstone is almost certainly one of them and is, in my view, the first one erected, long before the Stone Circle was envisioned. Some suggest that the nearby Stone-97 hole is actually its solutional pit, but I very much doubt it for a variety of reasons.
The Slaughter Stone and its missing twin, Stone-E, are also candidates. Those were most likely Stones -B and -C, used during the earlier incarnation, eventually moved when the alignment changed.
On the other hand -- for what it's worth -- I do believe all the Trilithons came from 'away'.

3) It's now widely accepted that the North Barrow is the oldest feature at Stonehenge; predating the Ditch and Bank by quite a while. There's no way of knowing how or when the bluestone chips were introduced, but as the Barrow was significantly altered from its original state this suggests that the chips could have been deposited at the time the blues showed up for use in the Aubreys. It would be valuable to pursue that research.

Best Wishes,
Neil

BRIAN JOHN said...

Neil -- the periodic melting of permafrost does not cause stripes. Nobody has ever shown me any reason why those "stripes" have anything to do with permafrost or any reason why the word "periglacial" needs to be used at all. I reckon one of MPP's mates came up with the word because it sounded learned, and it just stuck! Periglacial striped ground involves the lateral sorting of sediments on a gentle slope where previously the sediments were unsorted. I see no evidence for that process ever having happened in this context.

Myris of Alexandria said...

Yes some good thoughts/gloss but some sleight of hand too.

I think it would very useful were you to do a post outlining periglacial striping, a post that can be used and cited.

Just a text-book explanation no reference to any Wessexellian localities.

I agree that all debitage is based on the investigated debitage. How else can you do it.

Yes the un-excavated parts of SH may contain kilos of emerald-veined kryptonite (and of course the 'lost' sarsens that completed the circle) even and, I agree this is pushing it, the Lost kingdom of Mu.

What can be said is that the debitage sample and the ratios of the lithologies found in that debitage are remarkably uniform throughout the SH Landscape.
That the extant non-dolerite orthostats do not seem to be part of that debitage <<1%
That almost ALL >95% of the rhyolitic debitage is from CRyf and much from the planar quarry face.

Incidentally it rather suggests that the debitage is not dressing but destruction.

You cannot have your cake and eat it. All discussion is based on present knowledge to dismiss that because it is not 100% leads us to chav'sville pseudoscience.

Great New Year to you too 'Agios Kostas, will be in touch. I am sure Bran misses you here, I know that I do. Perhaps this year will be kiss and make up and your return.

Clap hands boys and girls if you want Kostas back. Panto season really is the best of British theatre (pace Swans).
M


Neil Wiseman said...

Brian,

Far be it for me to presume complete knowledge on this aspect, but having said that: what, in your view, caused the stripes?
Glacier? If so, the stripes infer scraping, which infers entrainment, which infers a moraine? Where's the moraine?

If this glacier chugged all the way from Wales carrying bluestones, why did it not also scrape up existing deposits of stone we know were in the vicinity?
The many beds of sarsen north of the Pewsey Vale don't appear to have been disturbed by a glacial event. (When one is lifted, there's chalk under it.) The same is true for the far fewer deposits of sarsen south of the Vale.

The stripes were initially detected by GPS, and the entire landscape around Stonehenge has been investigated with this technique. This slope is really the only place in the area where they seem to exist. Is this not inconsistent with glacial entrainment?

These remarks are not intended to be incendiary, but I'd really like to know the answer to some of them.

Neil

BRIAN JOHN said...

Periglacial stripes? I have doe it to death already, Myris. Just use the search box. The "stripes" look like solutional rills and they probably are solutional rills, which may have evolved during temperate and periglacial climatic conditions. As I have said many times, their alignment and spacing may be influenced by bands of flint nodules or other irregularities in the chalk bedrock. this is what Field et al are also suggesting in thus paper.

Debitage -- Myris, if you are not to be accused of pseudoscience, and want to be taken seriously as a scientist, you need to be careful about how you phrase things. I have taken you to task about this before, and will continue to do so..

"Planar quarry face" -- there ain't no such thing. Just because you keep on using that expression does not make it any more true. When you have acknowledged and addressed (in print) the issues raised by Dyfed, John and me in our 2 peer-reviewed papers, I may take your assertions more seriously. Until then, we have a fracture-guided rockfall face characterised by multiple surfaces, some of which appear to be guided by foliations within the rhyolite bedrock. It's all here, on the blog, and in print. Until you acknowledge and address our work in print I fear you are solidly stuck in scientific misconduct territory, and I shall continue to say so.

BRIAN JOHN said...

Neil -- forgive me for saying so, but you are getting in a bit of a tangle here. The stripes have nothing to do with glaciation, as far as I can see, unless they have something to do with enhanced surface run-off associated with an ice edge. But then you would expect to find fluvioglacial gravels at the bottom ends of these runnels -- and as far as I am aware, none have been found.

Glaciers do not need to "plough up" or remove embedded stones on the ground that is being overridden. Sometimes that happens, where bed erosion is going on (depends on bed temperatures, ice velocity and many other things) and sometimes ice will pass across terrain (including fragile "tors" as Adrian Hall has shown) which remain apparently unaffected. In those circumstances ice plays a protective role. I suspect that may happen where there are very cold conditions and where there are large accumulated snowfields prior to ice arrival -- the ice is then classified as having a "polar" regime rather than a temperate one.

Can I gently suggest that you look up "entrainment" on this blog?

Jon Morris said...

Solutional rills look more likely to me. I remember the arguments at the time. Must have been a while back though?

The little mound: Anyone know why they assume it to be natural? Seems a bit of a stretch to make this assumption without any excavation.

(The Geo-hyp sequence would ideally have a small pre-construction earthwork feature in this position for construction purposes.)

Myris of Alexandria said...

I am unable to give any informed discussion on your sedimentolgical work and so have refrained from doing so.
However I have worked in quarries since the first moon landings -my Ph.D ws built around Masson Hill Quarry and I have seen and worked in quarries in a number of countries. I know quarry faces very well and what the rock fall from them looks like.
CRyf is not a natural planar surface it is not a fault plane or master joint plane
your point about the surface being irregular is naïve, indeed the fact that there are joint blocks sticking out confirms this is not a natural planar shear surface.

The proto-orthostat's orientation is just icing on the cake.

There has been quarrying at CRyf on that quarry face. No amount of sedimentology is going to alter that.

My earlier and far longer post has become attenuated in the aether it seems.

M

BRIAN JOHN said...

Myris -- I am not going to accept your protestation that "I know a quarry when I see one" since you have not at any stage described which features cannot have been made by a natural sequence of shearing events and rockfalls such as we see on exposed rock surfaces all over the place. I have compared it with the rock face at Abermawr South -- check out the post on that. There are multiple surfaces here, and I do not understand your point about it "not being a natural planar shear surface." Too right it isn't -- because it is made up of many shear faces, some at least 1.5 m further out than others. There are multiple crossing or intersecting fractures. The rock face is a mess -- and there is nothing unnatural about it. We explained all this in our papers -- and you and Richard have ignored the points we made rather than entering into a proper academic debate about them.