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Monday, 21 March 2011

The Stonehenge Moraine?

Looking afresh at the Judd article from 1903, and recalling the ideas of Geoffrey Kellaway, maybe the time is right to resurrect the question of whether there might have been a moraine at or near Stonehenge, laid down a very long time ago (during the Anglian Glaciation) at the easternmost extremity of Irish Sea Glacier advance.

I know that certain geomorphologists, including Prof James Scourse, Prof David Bowen and Dr Chris Green, have rubbished this idea with great enthusiasm, claiming that it is glaciologically implausible and unsupported by any field evidence.  As I recall, all three of them have used the word "impossible" -- causing me to recoil in horror and the archaeological establishment to rub its hands in glee.

But Wesley John Judd (he must have been a good Methodist, with a name like that, so maybe he enjoyed divine inspiration) was no fool.  Look carefully again at his paper.  He clearly was not too sure where the ice had come from (north or west, or maybe north-west) but he clearly had suspicions that the assemblage of debris at Stonehenge had come from North Pembs or North Wales.  He also observed that in areas affected by very ancient glaciations, most of the till would have been eroded away by river action and solifluction after hundreds of thousands of years, leaving only a thin scatter of erratics here and there.  Further, he observed that scattered hard stones (including bluestones) left behind on Salisbury Plain would have been targetted down through the centuries for building purposes, millstones etc -- and this was a point also made quite forcefully by Olwen Williams-Thorpe and her colleagues during the Open University studies around 1990.

Things get even more interesting when we look at his identifications of stones.  He seems to have concentrated not on the bluestone monoliths or orthostats themselves, but on the debitage or debris in the Stonehenge soil layer.  And what did he identify?  An extraordinary assortment of "rubbish stones" including fissile sandstones, micaceous sandstones, greywackes (argillaceous and easily broken down), flagstones, slates and "clay-slates", and fine-grained glauconitic sandstones.  He made the point specifically that all this material did not seem to be very closely related to the remaining standing bluestones -- so he concluded that only the hardest stones had survived to the present day, with all the rubbish material breaking down and becoming incorporated into the soil layer over many thousands of years.

What if all that debris was in the soil layer long before Stonehenge was built?  It's perfectly feasible. Might we therefore be looking at the remains of an ancient till deposit, or even a moraine?  Judd himself seemed to think -- right at the end of his note -- that the presence of this feature -- with an abundance of foreign stones readily available to the builders of Stonehenge -- might have actually determined the precise position of the monument.  Nothing to do with ley lines or astronomy or anything else of an esoteric nature -- straightforward opportunism on the part of the tribes who lived on Salisbury Plain.

Now I'm not familiar with all of the details of the current geology, and I need advice on all of this, but it seems that there are clues in the recent work published by Rob Ixer and Richard Bevins that suggest that Judd was pretty much on the ball.  They have already said in print that much of the debitage is unrelated to the nature of the bluestone monoliths.............

One further intriguing thought comes into my head.  It's difficult to know from Judd's descriptions precisely which sedimentary and metamorphic rock types he is talking about -- names have changed over the years.  But when he talks of fissile sandstones, greywackes, slates, flagstones, clay-slates and so forth he could well be describing the non-volcanic rock types that occur in association with the Fishguard Volcanics in the eastern Preseli Hills and Dinas-Newport area of North Pembrokeshire.  If you walk around the area today the intervening areas between the volcanic and intrusive rock outcrops (the rhyolites and dolerites) are underlain by shales, mudstones, sandstones and ash beds, sometimes in an unaltered sedimentary state, sometimes partly metamorphosed, and sometimes transformed into slate.

So could this non-igneous debitage also have come from this same narrow zone (about 3 km wide) which I have already speculated on as a possible zone of entrainment between Welsh Ice and Irish Sea ice at the time of the Anglian glacial episode?

More and more intriguing --- watch this space.


Tony Hinchliffe said...

What a pity the River Till, to the west of Stonehenge near Tilshead, does not in reality owe the origin of its name to glacial till! I think the 'river' is a winterbourne, only flowing a few months in the winter, and that it took its name from Tilshead during Victorian times. The 'Til' element is from an Anglo-Saxon name.

However, I have seen somewhere that
Aubrey Burl has remarked on the likelihood that the bluestones were recovered by prehistoric man somewhere in the broad vicinity of Chitterne and Bowls Barrow, west of Stonehenge.

The Stonehenge Enigma said...

" with an abundance of foreign stones readily available to the builders of Stonehenge -- might have actually determined the precise position of the monument. Nothing to do with ley lines or astronomy or anything else of an esoteric nature"

Are you suggesting that Stonehenge was built at a point were a moraine ended?

If you look at the elevation levels at Stonehenge they show that it was built halfway up a hill with massive ditches on three sides - see or the youtube video I made about Stonehenge for diagrams of the area.

A natural ice sheet would leave this debris at the bottom of the slope not halfway up as it would follow the natural contours of the terrain.

Consequently, I do agree with is that "most of the till would have been eroded away by river action and solifluction after hundreds of thousands of years, leaving only a thin scatter of erratics here and there"

As my inundation theory clearly proves.

You may also find my new blog site of interest as it shows that the European Ice Cap may have resulted in ancient 'Long Barrows' navigation aids in northern Europe including Stonehenge.

Further proof of higher water levels in the Mesolithic Period and the main reason you find ice sheet evidence elusive as it was simply washed away.


BRIAN JOHN said...

Tony -- yes, Chitterne and Bowls Barrow figure in a number of articles. Kellaway liked the idea that there is something strange at Chitterne -- in an old sinkhole....

Robert -- the term "moraine" is a loose one -- and moraines are not necessarily long and winding ridges. many areas of moraine are utterly chaotic, with no linearity to them at all. Maybe the terms "till sheet" or "boulder clay spread" would be more understandable. And there is no reason whatsoever for morainic debris to be left in the bottom of a valley rather than on the slopes or even on the summits of hills. if ice is downwasting catastrophically it can dump moraine and erratics ANYWHERE on an undulating landscape.

Tony Hinchliffe said...

Most Methodists I have known have been hardworking, essentially practical people one can admire. It seems likely that John Wesley Judd falls into that category. His conclusions seem to have been carefully considered first.

Tony Hinchliffe said...

Brain, do tell us more about the "something strange at an old sinkhole" you mention above. I am intrigued.

BRIAN JOHN said...

As a Methodist myself, who am I to disagree?

I'll dig up the stuff about Chitterne...

BRIAN JOHN said...

Something Strange at Chitterne

Re: the Chitterne sink hole. There was a tradition that the sink hole (according to Geoff Kellaway one of the deepest sinks holes on the downs) was the place where the Stonehenge sarsens came from. Geoffrey says that the sides of the sink run vertically for at least 10m.

Isobel Geddes: "I went to this site 10 years ago -- - there is just a hollow in a wood on a hill with no rock (or even Reading Beds) to see! Details are as follows: Claypit Hill, Chitterne.(ST 994425). This former aggregate extraction site provides a unique occurence of sands and clays (thought to be Reading Beds) on the chalk plateau of Salisbury Plain. The strata owe their preservation by having collapsed, several m.y. ago, down into a major solution hollow in the chalk some 250m across and of unknown depth. They provide the only direct evidence of strata formerly overlying the chalk in this part of Wiltshire - the nearest Reading Beds outcrop is over 14 miles to the S.W."

Tony Hinchliffe said...

Battlesbury Hill and Scratchbury Hill (ironically, both used by prehistoric man as Iron Age hill forts - Scratchbury also has a Neolithic causewayed camp) lie broadly north-west of Stonehenge and could have provided severe obstacles to glacial movement from a similar direction. Scratchbury in particular has tremendous panoramic views from the top, taking in Cley Hill and Boles Barrow, for example. Today, of course, the Army occupies much of the land to the east and north-east. They have built their own tank roads near Battlesbury and beyond, after consultation with the then County Archaeologist, Roy Canham. Roy is these days leader of that Salisbury Plain Training Area's Archaeological Sub - Group and has been honoured by the Queen for his work, paricularly as respects The Plain.

Anonymous said...

Sweet dreams are made of this
(Brian said) Who am I to disagree?
Travel the world & the Seven Seas
Even Neolithic tribesmen were lookin' for something
Some of them were after new stone
Some of us just want BLUE stone
Never felt more like singin' the Blues
Glaciation's the new creation....
Academics tend to disagree
Maybe Bobby Dylan can set us free