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Sunday, 22 January 2012

Those periglacial stripes are probably not periglacial



I have devoted some space before to those strange features examined over the years by archaeologists and generally referred to as "periglacial stripes" -- and referred to, with delightful quaintness, as "geological stripes" or "natural Ice Age gullies" by EH.  I've done a bit more digging into the literature -- a poor substitute for digging into the ground -- and I am increasingly convinced that they are not periglacial in origin.

Here are the latest EH statements about them -- probably guided by MPP and his team, who have most recently examined them:

Recent excavations and geophysical surveys have suggested the possible importance of geological features called periglacial stripes. They run parallel to the banks of the avenue and across the site of Stonehenge and align in places on the solstice axis. It is possible that these geological stripes may have been visible on the ground in early prehistory and could have led prehistoric people to believe that this was a special place.

http://www.english-heritage.org.uk/daysout/properties/stonehenge/history-and-research/history/
Outline of the main differences between the 1st edition of the
English Heritage Stonehenge guidebook (2005, reprinted 2007)
and the 2nd Edition (2011) (download as PDF)

v) The possibility that Stonehenge's location was chosen as a result of the
coincidental alignment with the solstice axis of natural landscape features
(periglacial stripes underlying the Avenue) coupled with the occurrence of a natural
sarsen (the Heel Stone) at the end of that alignment. 

A new paragraph has been added discussing the discovery of the existence of
natural Ice Age gullies parallel to the Avenue, and the possibility that the Heel
Stone is a rare local sarsen found near where it now stands, both features
providing a coincidental alignment on the solstices. It is suggested that this may
have provided the impetus for the building work that followed.

Added mention of the natural "visible stripes" that are Ice Age landscape
features in the chalk parallel to the Avenue along the straight section leading up to
the monument. Changed emphasis in discussing the solstice axis from "this cannot
be a coincidence" to "this alignment is deliberate".



Beware of optical illusions on this LIDAR image --if you are not careful the low parts of the landscape can look high, and vice versa......




 Vertical satellite image of the Avenue, running from Stonehenge (bottom L corner) 
towards the NW

If the evidence is reliable that these stripes run parallel with the first part of the Avenue (shown in both of the illustrations above) and even run through or beneath the Stonehenge earthworks, then that clearly suggests a great age for the features.  But we don't really know how extensive they are -- maybe somebody who knows the evidence on the ground can enlighten us on that.  If you look very carefully at this illustration you can see a faint line outside the Avenue edge which is interpreted as one of the "periglacial stripes."





What we need here is a detailed topographic survey, but my impression is that these stripes (like the Avenue) point towards the midsummer solstice or sunrise position on the horizon (have I got that right?) but that they do NOT run down the maximum slope inclination towards Stonehenge Bottom.  If there is one thing we do know about periglacial stripes it is this:  they always run down the maximum inclination of the slope.  I have seen a lot of such stripes in my time, in Antarctica, Greenland and Iceland, and I do not recall a single one that was aligned diagonally down a slope. 

In the absence of a detailed survey all I can do is speculate about this -- and to say that if these stripes really are periglacial in origin, they should be running from Stonehenge down towards the road junction we can see on the LIDAR image.


Far be it from me to suggest that something perceived as "natural" in origin should now be re-classified as "probably man-made" -- but that is exactly what I am doing!!

24 comments:

Anonymous said...

Brian,

“Far be it from me to suggest that something perceived as "natural" in origin should now be re-classified as "probably man-made" -- but that is exactly what I am doing!!”

Does this also mean all those 'stripes'? Robert's 'cart tracks' maybe?

BRIAN JOHN said...

Well, it's all up for grabs. If the "stripes" are genuinely diagonal to the contours -- rather than perpendicular -- I don't think they can be periglacial in origin. Neither can I think of any other obvious natural explanation, unless there is some structural control over the solution / weathering at the base of the regolith.....

Phil M. said...

Hello Brian,

A quick look at 'Where's the path' shows The Avenue running along a spur before dropping, and turning right to run off a second spur.
Perhaps someone with access to a copy of the Ordnance Survey map of the area can give more information.

Phil M.

BRIAN JOHN said...

Agree, Phil. My impression precisely. What we need is much more detailed contouring -- there must be such a map somewhere....

Phil M. said...

Hello Brian,
I am not at home this weekend so have only limited access to information.
However, Aubrey Burle, The Stonehenge People, 1987, page 4 says:
"Then, as late as 2200BC, people brought some Welsh bluestones to the site, started to set them up in two circles, one inside the other, and constructed an avenue, undeviatingly straight, up the northern hillside towards the henge's entrance."
This would indicate a slope away from the monument,which is counter to the limited number of contours on the map; so we shall have to await confirmation from one, or more, of our learned bloggers.

If the stripes are man-made, then would it not be difficult for a large number of people to 'process' along/over such an undulating surface; twisted ankles comes to mind.

Phil M.

Tony H said...

Re the periglacial stripes notion: quoting from "If Stones Could Speak" (Marc Aronson with help from MPP; National Geographic, 2010 ISBN 978-1-4263-0600-6):-

"There are many natural ridges in te landscape near Stonehenge. On the gentle hill leading down from Stonehenge, two of these ridges form parallel lines. In June of a dry summer,not much grass would growshpe of the land would be clearly visible.

Peraps on one midsummer's day, a person saw the rising sun inching along the ridge lines to the top of the hill. On that one special day, the sun rose exactly along those straight lines. Maybe the ripples suggested the Avenue and pointed to the place for the ring and the stones. Indeed we know that the avenue on that hillside was later formed by adding earth on top of the natural ridges."

Apologies for missing words, etc, computer is baffling me currently!

Anonymous said...

Brian,

We have a problem! If we can conclude the Avenue stripes were “probably man-made” with no evidence, why can't we conclude Neolithic men carried the bluestones without any evidence?

Geo Cur said...

Tony , the Aronson comment is a bit confusing ,if you were looking along the lines of the ridges up towards the monument on midsummers day the sun would be rising behind you . If he had said on midwinters day it would make more sense ,the direction of lines would be pointing to where the sun would be seen to set behind the monument . To see the sun rise along the line of the stripes would mean looking away from the monument and it wouldn’t be inching along it would be going up and heading south .

Jon Morris said...

If you wish to create a kind of Ampitheatre for people to watch an event, ridges leading from the Avenue might help.

What other purpose might man made ridges have?

BRIAN JOHN said...

Anon, the difference is that there is a perfectly sound natural explanation for the transport of the bluestones (backed up by field evidence) but that the natural explanation for the "periglacial stripes" seems to me to be somewhat defective. Mind you, this one isn't finished yet -- I remain to be convinced that the stripes are long and continuous -- maybe they are very localised and are found just around the Avenue entrance, where there has been a lot of messing about with post holes etc?

Tony H said...

GeoCur

yes, entirely my thoughts when I read this Marc Aronson National Geographic book statement!

There may well be, on the Time Team's website, a downloadable recording of their Time Team Special on Stonehenge (probably the most recent of several).

Dr Phil Harding and Mike Parker Pearson are to be seen in conversation with Tony Robinson, on site but after the excavations had been back-filled, discussing the relative merits and demerits of 'dem glorious PERIGLACIAL [OR NOT] STRIPES.

To be continued...........??!

Robert John Langdon said...

Brian

You are a strange man!

Why block a comment that answers your question "these stripes (like the Avenue) point towards the midsummer solstice or sunrise position on the horizon (have I got that right?)"

Yes you have got it right and its 4260BC - how do we know this - they found an antler pick under Sarsen Stone 27 and carbon dated it - then ignored the evidence, this date coincides with the summer solstice sunrise 'in the centre' of the Avenue.

If you wish to delete this 'FACTUAL' evidence that's fine - but don't call yourself a scientist if you do!

RJL

BRIAN JOHN said...

Robert -- call me strange if you like, but I do sometimes block comments from people on hobbyhorses. If the submitted comment contains something factual which might or might not be reliable, I am not going to start filtering that out from the general context. Life's too short....

Anonymous said...

Brian,

If the stripes are parallel to the Avenue and running diagonally to the contour lines (as does the Avenue) and therefore not periglacial as you argue, but probably formed by men as you now believe … what would be their purpose? RJL's cart tracks? And if this question is beyond your expertise and leave it to the experts to sort out, do you now also believe the archeologists explanations about Neolithic SPAs at Stonehenge and Cursus processions around a ceremonial promenade and Bluehenge-Stonehenge /living-dead cremations?

Where do you now stand with all that before you have opposed? What are we to make of you now? You seem to be contradicting yourself!

Anonymous said...

Brian,

“ I do sometimes block comments from people on hobbyhorses”

Archeologists also think you are on a hobbyhorse!

BRIAN JOHN said...

Mine, I think, is galloping on reasonably firm ground.

BRIAN JOHN said...

Kostas, I assume this is you lurking behind anonymity again -- I am not contradicting myself in the least. Like any conscientious scientist, I look at stuff and seek the most sensible explanation. It just so happens that I have problems with the "periglacial explanation" for those stripes. Is that such a big deal?

Tony H said...

I am sure there are some "virtual" computer imaged tours of The Avenue lurking around on the Web. Let's see if anyone out there knows of their location. Their marketability has increased with the discovery of the so-called "Bluehenge" at the Avenue's junction with the River Avon. Perhaps GeoCur knows? Or PeteG?

Anonymous said...

Brian,
“ Mine, I think, is galloping on reasonably firm ground.”

It's not how firm the ground is, but whether you are heading in the right direction!

BRIAN JOHN said...

That's life for you in all its richness....

Anonymous said...

That's life for you in all its folly....

Anonymous said...

http://www.stonehenge-avebury.net/Panoramas/StonehengeAvenue.html

for a panoramic tour along the avenue during the digs.
PeteG

BRIAN JOHN said...

Thanks Pete -- can't view those -- do you need some special viewer installed on the computer?

Anonymous said...

if you are using a Mac install a java plugin for Safari and make sure your OS is uptodate.
PeteG