Clean ice and dirty ice

 

I was looking through my old slides from Axel Heiberg Island in the Canadian Arctic when I came across these two.  These are two glaciers within a kilometre or so -- one which is virtually free of dirty ice, let alone till, and the other flanked by a very distinct morainic ridge and with layer after layer of dirty ice, filled with englacial debris.

It's not so mysterious -- glaciological principles are at play here. But it is intriguing nonetheless that one glacier can advance and retreat across the landscape leaving virtually no trace of its coming and going, while another (right next door) leaves quite a dramatic legacy of sediments and landforms.

The West Kennet Bluestone Assemblage

 

Following on from the revelations of Josh Pollard in his recent video talk, I have been pondering on what the collection of foreign stones at West Kennet should be called.  They had better be called "the West Kennet bluestone assemblage"  since there seem to be a lot of them  -- and at the moment all we know about them is that some of them, at least, are made of granidiorite from far to the north. It has not yet been demonstrated that all of the fragments and stones are from the same source, let alone from a single boulder that has fallen apart or been smashed up -- we await a paper from Ixer and Bevins, which will no doubt tell us the truth of the matter.

As we all know, the term "bluestone" is used for any non-sarsen stone that pops up on Salisbury Plain, most often (but not always) in the vicinity of Stonehenge.  As as we are also fully aware, there are around 30 different provenances included in the currently known Stonehenge bluestone assemblage. The bluestones recorded thus far are not all from the Mynydd Preseli - North Pembrokeshire area;  and since the Altar Stone is apparently not from Pembrokeshire at all, and is in any case afforded the "bluestone" label, it is entirely logical to call any stones from the Cheviot area or elsewhere in Northern England bluestones as well.

As I have noted before, it is more and more apparent that bluestones are scattered over a wide area and that it is a mistake to label all of them as "STONEHENGE bluestones."  The scatter of bluestones around Fargo Plantation is rather intriguing, and it looks as if there was an "independent" source of fragments somewhere near there.  It has already been mooted by MPP and his colleagues that there may have been standing bluestones there, and maybe even a circle of rhyolite standing stones -- but there is no reason at all to assume that those were the same stones as we currently see at Stonehenge.  See Chapter 4 of "Stonehenge for the Ancestors":

https://www.sidestone.com/books/stonehenge-for-the-ancestors-part-1

Then we have the highly controversial Boles Barrow site, which we have discussed at length.  And now West Kennet and "Structure 5"..........

http://exploringavebury.com/book-notes-134-140

I still think that there may well be quite large bluestones that are as yet undiscovered.  It is notoriously difficult to distinguish bluestones from sarsens in the field, since they have very similar colouring and similar shapes -- and it's only when you examine them closely that you can pick up the textural characteristics of dolerite, rhyolite or volcanic ash.  As for the Palaeozoic sandstones -- telling them from sarsens is even more difficult. 

It starts to get rather interesting.  Who knows where it will all end?

The Millennium Stone fiasco -- a photo gallery

How not to move a bluestone from A to B.  This is in the nature of a happy family album, some of the photos shared by the happy band of brothers and sisters who hauled the Millennium Stone on its ill-fated journey from Mynachlogddu towards Stonehenge.  Not very far towards Stonehenge as it happened, but there was a lot of camaraderie, and it was good fun........

 

 

Breaking news: another igneous erratic (or several) on the Wiltshire chalklands

One of the lumps of granidiorite found in the West Kennet excavation.  From Josh Pollard's talk.

https://www.wiltshiremuseum.org.uk/?event=online-event-connections-avebury-and-orkney&event_date=2021-11-26&platform=hootsuite&utm_campaign=Castle&fbclid=IwAR0tfR0Wtlt_dIA086d9VTMkan7bHy9lgRCt-RbuT1c5ug3kD6t1SrZHFaw

According to some posts on Facebook, quite a few people have known about this for quite a while, but now Josh Pollard has formally announced the finding of erratic material (a lot of it) from "Structure Five" at West Kennet, not far from Avebury.  The material appears to be a very distinctive form of granidiorite from the eastern edge of Cheviot.  According to Josh, the geologists (Ixer and Bevins) have provenanced the rock type to Cunyan Crags, near Dunmore.  It's very crumbly and heavily weathered, and from the lumps of rock collected from various parts of the excavation, there are at least 130 kg of it -- and probably a lot more.  Did the lumps of rock all come from a single erratic, or could there have been several in the vicinity?   Josh -- of course -- assumes that the boulder or boulders might have been "direct or indirect" imports, but then he's an archaeologist who has an established preference for the human transport of large lumps of rock, and a reluctance to believe that ice is capable of carrying large stones over great distances and dumping them anywhere near Salisbury Plain or elsewhere in Wiltshire.   The suggestion in the talk is that these lumps of rock (found  mostly in post holes) are from a destroyed standing stone -- but there is currently no evidence to support that.  He does note that no lumps of the granidiorite have been found on the surface -- and he assumes that any that did exist have simply been weathered away.  Even the lumps that have been examined are more or less reduced to "grus" (the crumbly residue left when granitic rocks rot away) -- and that all suggests great age.

But we can rest assured that the southward transport of igneous material from the far north was not just possible but probable, during the Anglian and earlier glacial episodes.  In 1999 Olwen Williams-Thorpe and others described the occurrence of Whin sill quartz dolerite and many other far-travelled northern erratics in the glacial deposits of Hertfordshire and Buckinghamshire:

Note that this map from 1999 is now somewhat dated.  The outer ice limit as shown is very inaccurate; ice extended at least as far to the SW as the letter (a) on the map.

"Geochemical provenancing of igneous glacial erratics from Southern Britain, and implications for prehistoric stone implement distributions" by Olwen Williams-Thorpe, Don Aldiss, Ian J. Rigby, Richard S. Thorpe, 22 FEB 1999, Geoarchaeology, Volume 14, Issue 3, pages 209–246, March 1999

http://onlinelibrary.wiley.com/doi/10.1002/%28SICI%291520-6548%28199903%2914:3%3C209::AID-GEA1%3E3.0.CO;2-7/abstract

Abstract

Sixteen basic and intermediate composition igneous glacial erratics from Anglian (pre-423,000 years) deposits in Hertfordshire and Buckinghamshire, southern Britain, were selected for chemical and petrographic analysis in order to determine their original source outcrops. Major and trace element compositions suggest that seven samples (plus two uncertain) originated in the Lower Carboniferous volcanics of the Scottish Midland Valley (SMV), four came from the Upper Carboniferous quartz dolerite association which crops out in Scotland, northern England (Whin Sill) and extends to Norway, and one came from the northern England Cleveland Dyke. One sample of altered dolerite is ambiguous but has some similarity to the Old Red Sandstone (Devonian) age lavas of the SMV, and one meta-basalt sample may be from southwest Scotland or Scandinavia. These results identify specific outcrops which provided glacial erratics within currently accepted ice trails in the United Kingdom, and provide the first supporting evidence based on geochemistry, rather than petrography, for these ice movements. The distribution and provenance of glacial erratics are of importance in archaeological studies, because erratics provided a potential source of raw material for stone implement production. There is a marked geographical correlation between the distribution of prehistoric stone implements of quartz dolerite in the United Kingdom, and directions of ice movements from quartz dolerite outcrops within Britain. This correlation lends support to the hypothesis that prehistoric man made extensive use of glacial erratics for implement manufacture, as an alternative to quarrying at outcrops and subsequent long-distance trade.

In other papers Olwen and her colleagues have also noted the presence of other "inconvenient" erratics in archaeological contexts:

The Geological Sources and Transport of the Bluestones of Stonehenge, Wiltshire, UK
Proceedings of the Prehistoric Society , Volume 57 , Issue 2 , 1991, pp. 103 - 157
DOI: https://doi.org/10.1017/S0079497X00004527

Published online by Cambridge University Press: 18 February 2014
Richard S. Thorpe , Olwen Williams-Thorpe , D. Graham Jenkins , J. S. Watson , R. A. Ixer and R. G. Thomas

From the Abstract:

‘Bluestone’ fragments are frequently reported on and near Salisbury Plain in archaeological literature, and include a wide range of rock types from monuments of widely differing types and dates, and pieces not directly associated with archaeological structures. Examination of prehistoric stone monuments in south Wales shows no preference for bluestones in this area. The monoliths at Stonehenge include some structurally poor rock types, now completely eroded above ground. We conclude that the builders of the bluestone structures at Stonehenge utilized a heterogeneous deposit of glacial boulders readily available on Salisbury Plain. Remaining erratics are now seen as small fragments sometimes incorporated in a variety of archaeological sites, while others were destroyed and removed in the 18th century. The bluestones were transported to Salisbury Plain from varied sources in south Wales by a glacier rather than human activity.

This map shows Cheviot and the directions of ice movement during the Late Devensian glacial episode:

Was it possible that the erratic(s) from Cheviot were carried by ice all the way (c 480 km) from Cheviot to West Kennet and Avebury?  I wouldn't rule anything out.  The Anglian ice edge is most frequently shown as lying some distance north of Salisbury Plain,  but clearly much more research is needed, particularly on some of the deposits conveniently lumped into the "clay-with-flints" category -- and the discovery of this new erratic occurrence keeps the debate bubbling along nicely.

Rescuing the Millennium Stone: historic photo

 

I discovered this very rare and historic photo showing the rescue of the Millennium Stone after it had slipped into the Eastern Cleddau river in the year 2000.  This was taken a day or two after I had helped with the pulling of the stone on its sledge.  It fell into the river when assorted volunteers tried -- using authentic techniques -- to transfer the stone from the river bank into a curragh that was afloat, round about high tide.  Anyway, in order to recover the stone, authenticity had to be temporarily suspended, as it was on every single day of the ill-fated bluestone transport expedition.  The full and exciting story is related in detail in the pages of "The Stonehenge Bluestones". Available from all good bookshops!

Next time those enthusiastic experimental archaeology people show you one of their photos demonstrating how easy it is to pull a bluestone across a nice flat college lawn or a grassy London park, show them this photo as well..........

Patagonian brash ice

 

Came across this very unusual photo.  Brash ice (broken fragments of glacier ice from a floating ice edge) on the shore of an ice-dammed lake in Patagonia -- coming in very handy as cover for a hunting mountain lion. Otherwise known as a cougar, puma or panther.........

One of the chapters for my book "World of Ice" was about the wild life associated with glacial environments.    Some of the adaptations are really rather splendid.

Megaphone archaeology

 

Here we go again.  A big article in the Guardian, based on info fed to it by Vince Gaffney and relating to the supposed "mega-circle" of giant pits in the Durrington - Larkhill area.  The "circle" is no more circular this year than it was last year.

It's here, in all its glory:

https://www.theguardian.com/science/2021/nov/23/new-tests-show-neolithic-pits-near-stonehenge-were-humanmade

Other media outlets have picked up on the story as well, so as not to be outdone by the Guardian.

This is all based on third-hand information and speculation, issued now in order to drum up interest in a new programme to be shown on December 9th on Channel Five.  No mention of flint mining or flint excavation pits or enlarged solution hollows for the purpose of finding flint nodules.  No data, no evidence -- just excited hogwash which we are all expected to believe because there is no way to scrutinize what has actually been discovered.    Maybe there is another paper somewhere in the pipeline, and maybe not.  This is real megaphone archaeology, using the media and press releases as a substitute for sound academic research and peer review.

Programme title: Stonehenge: The New Revelations. This is a couple of miles away from Stonehenge -- but that's the word that pulls the viewers in, so what the hell.......

I thought archaeology was in a bad way, having looked in detail at the working methods of our old friend MPP.  This is now confirmed.  And how.

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

PS.  This is what Gaffney et al said in the discussion at the end of their original paper:  

Given the presumed later Neolithic date for the pit group, the size of the features, and the scale at which the circuit of pits has been implemented, it is difficult to identify directly comparable groups of features within the British Isles. In respect of clustering of large pits, those associated with, generally earlier, flint mines may invite consideration (Field and Barber 1998; Barber et al. 1999; Mercer 1981). In some instances, such as Cissbury hillfort, large pits associated with mining do form linear alignments; presumably following seams of flint within the boundary of the later Iron Age hillfort (Barber et al. 1999, 29). More locally, work by Booth and Stone (1952) and Stone (1958) record the presence of flint mines near Durrington. However, the illustrations provided by Stone demonstrate that these features are significantly narrower at the entrance than those described above (Figure 21). When considered spatially, Stone's features are also unlikely to be directly linked with the arcs of massive pits presented within this article. While it is not impossible that flint extracted from these pits may have been used on an ad hoc basis, the structural arrangement of the pit group around Durrington Walls, and their apparent link to the area of the henge monument, suggest that such a prosaic interpretation is not sufficient as an explanation for these features.

This was right at the end of the paper, the authors having previously studiously avoided any mention of consideration of flint mining or the excavation or enlargement of solution hollows for the purpose of flint nodule extraction.  Occam's Razor appears to have been forgotten about.  The authors are so keen on seeing their giant circle (which seems to me to be fanciful in the extreme) and on flagging up "the mystery of the giant pits" that the simplest and most logical explanation of these features has simply been shunted aside.........

Source:

Gaffney, V. et al. 2020 A Massive, Late Neolithic Pit Structure associated with Durrington Walls Henge, Internet Archaeology 55. 

https://doi.org/10.11141/ia.55.4

Above: From the Gaffney et al paper in 2020.  The superimposition of the "giant circle" is speculative in the extreme.  If they had wanted a circle, they would have measured one out properly.

From the Stonehenge Research Framework document.  Note the areas of flint mining / flint pit creation, as known at that time.  Gaffney et al have simply found a few more.......