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Friday, 21 August 2015

More on the Stonehenge "periglacial stripes"



Thanks to Chris Johnson and Tony Marsh for alerting me to this.   Thanks also to Geomatics PLC.   It's a new LIDAR image of Stonehenge and the Avenue, showing the ground surface contours at 1 ft intervals -- this is very detailed work.

So what does it show us that we did not know before?  We have discussed to so-called "periglacial stripes" at great length -- use the search box for the relevant entries.  I am happy to admit that I have got it wrong -- I have interpreted the "grain" of earlier LIDAR images as showing that the alignment of the Avenue and the "periglacial stripes" is oblique to the prevailing surface slope.  This new image shows that the alignment is in fact perpendicular to the contours.  In other words, the Avenue runs pretty well exactly along the "nose" of a very slight ridge, except at its outer end, where it simply keeps going in a straight line to the far end of the spur.  So there it is on the flank of the spur rather than on the ridge top.

Tony has added the T-marks on the image so that we can see where averaged perpendiculars are located -- but these are subjective in the sense that the alignment of the downslope line will vary according to the width of the lateral spread of the sampled points.  If you see what I mean.......

We are talking about very subtle variations here -- just a degree or two.  So the message is that the Avenue has been build along the nose of the ridge, and maybe has nothing at all to do with solar or lunar alignments of solstices.  By the same token, the "periglacial stripes" are running pretty well directly downslope, as we would expect them to do in a periglacial environment.  But I still don't think they are anything to do with periglacial sorting or patterned ground processes.  They are not straight, and because of their internal characteristics I still think they are solutional rills just like the many thousands of others in the Stonehenge landscape.  Here -- at the SW end of the Avenue -- they  run pretty well parallel to the Avenue sides.  To left and to right they probably splay slightly, keeping more or less perpendicular to the contours and running directly downslope so long as there is a sufficient gradient.  That is what water does.

The trouble is that nobody has looked for these "insignificant" or "irrelevant" rills systematically, because the focus of attention has always been Stonehenge and the Avenue.


A fantastic image of the excavation that exposed these mysterious rills within the confines of the Avenue.  Courtesy Aerial Cam and Sarsen.org.  We can see that they are not straight, in cross-section we see two different wavelengths.  There are two gentle ridges with a hollow between them, and superimposed on those we see smaller rills which wind or weave their way downslope.   This all suggests that solution has been the prime process, and that water has been the agent of land surface change.  This is exactly what we would expect on gently undulating chalkland such as this.

26 comments:

ND Wiseman said...

Hi Brian

For what it's worth, I've always thought the rills were solutional.
Shortly after their discovery someone said "Glacier!", so I looked into the 'behavioral patterns' of ice. The stripes don't seem to follow any of the models in terms of formation by direct contact and this new LiDAR image appears to bear that out.

But then, it's the stripes themselves rather than their cause that is of interest. There are a number of reasons Stonehenge was placed where it is, and though I feel that the stripes play a role, they're not the only one.

Neil

BRIAN JOHN said...

Don't remember anybody ever saying these features are glacial. Vanishingly unlikely from my point of view, even though I am open to the idea that the Irish Sea Glacier pushed from the west into the vicinity of Stonehenge. Periglacial, maybe -- and that's the story pushed out by Prof MPP on the basis of evidence that is still a mystery to me and everybody else. I have done that theory to death, and still see no merit in it.

Dave Maynard said...

Can anyone see the rills on this, or any other Lidar?

Or on any other remote sensing technique for that matter?

Some variant of geophysics might, but it would be difficult.

Dave

Geo Cur said...


Tony’s graphic shows the contours with the points of steepest descent marked, not the rills /stripes /animal tracks .The “steepest descent “ is in relation to what is a very gentle slope .

BRIAN JOHN said...

Yes, Geo -- that's what I said. Dave, the rills are sub-surface, and well covered with soil, so we should not expect to see any surface expression of them.

Geo Cur said...



“and maybe has nothing at all to do with solar or lunar alignments of solstices.”
Considering that the avenue was built after the other components of the solstice alignment (there is no lunar/avenue association ) and is a continuation of that alignment , it seems likely that it is something to do with that alignment .

Dave Maynard said...

Therefore, the only evidence for the existence and direction of the rills is from this excavation trench? Comments on direction and extent of the rills are only based on deduction, no matter how good and experienced in understanding geomorphology the interpreter is.

I seem to remember Kostas going down this route! I don't mean to be provocative.

Dave

chris johnson said...

I find it remarkable that the Avenue is constructed on a very slight ridge. My eyes have not been able to detect this ridge in the course of several visits. Was the ridge more prominent in the past? Or were neolithic people more attuned to slight variations in terrain? Or perhaps there was an alignment toward celestial events?

Curioser and curiouser said Alice ...

BRIAN JOHN said...

Dave -- I have done other posts on this - please check. Why would you expect a smooth flat surface beneath the soil layer in chalk country? No way -- the surface is always rough and irregular, and full of rills and hollows caused by solution. Just look at the top of the cliffs along any stretch of chalk coastline......

chris johnson said...

Geo, when was the Avenue built? I don't recall ever seeing any data on this.

Dave Maynard said...

The upper surface of chalk is always variable, sometimes rough, especially in clay-with-flints and can be smooth like some, but not all of the big chalk downs. Even in these there are products of solution and lines which are bit like faults. I'm never very sure when looking at big exposures of chalk after the soil has been stripped off whether the effects of ploughing have contributed to smoothing. Ploughmarks are nearly always present, sometimes going in different directions.

I always found digging in chalk more interesting that in other subsoils, perhaps because all these marks show up better than the other soils. Of course there are also horrible types of chalk. And the fun of identifying chalk filled features dug into chalk!

Dave

Geo Cur said...


Chris , from “STONEHENGE, AMESBURY, WILTSHIRE CHRONOLOGICAL MODELLING :
Peter Marshall, Timothy Darvill, Mike Parker Pearson, and Geoffrey Wainwright .
p. 6.” In 2008, Richard Atkinson’s 1956 trench, C48 (Montague 1995a, fig 178) was re-opened and extended (Parker Pearson and Pullen 2008). A single antler pick [1027] from layer [045] in pit 056, one of a pair (the other being 055), dug within the east side of the
Avenue, was laid on the base of the pit prior to its backfilling. Three radiocarbon
measurements on samples from the antler (OxA-20011, OxA-20350, and SUERC-23205;
Table 1) are statistically consistent (T’=5.8; =2; T’(5%)=6.0; Ward and Wilson 1978) and
allow a weighted mean to be calculated (SAV 1027; 3827±17 BP). The antler is
interpreted as deriving from the digging of the pit and therefore provides a date for this
activity. “ and p.17
“The model for the dating of the Avenue is derived from Parker Pearson et al
(forthcoming (a)) and shows good agreement between the radiocarbon dates and
stratigraphy (Amodel=67%). In this model pit 056 is interpreted as post-dating the initial
Avenue ditch but pre-dating the re-cutting. The best estimate for the date of its
construction is 2430–2200 cal BC (95% probability; Last construction; ) and
probably 2370–2275 cal BC (68% probability) . “

I too find terms like ridge , downhill , etc to describe the landscape around the monument end of the Avenue a bit extreme . Almost on a par with SH being built "halfway up a hill "


Tom said...

Hi Brian

Whilst the arguments gone on, over whether the Stonehenge Avenue was man made or not, few people realize that it was not the first avenue to be built. And not by a long way!

These arguments, in fact, are pretty much old hat now that my book ‘Stonehenge before Stonehenge’ has been released on Amazon.

The book explains how the official ‘Stonehenge Avenue’ that everyone these days are arguing about, was not the first to be built - two others were made that were aligned upon the still visible stars of the Southern Cross, some 6,000 years ago.

Also, Brian, you asked for an answer to a question on your blog, “Are some stones meant to be female and others male? - Answers on a postcard, please.” This too, along with what I regard as proof of male and female stones, is answered in my book.
Cannot help you with the bluestone transport though!

Keep up the good work.

Tom Flowers

TonyH said...

Chris/ Brian:-

How did you come across this LIDAR imagery, is it and Geomatics PLC in any way connected to English Heritage's (as was) recent landscape work in the Greater Stonehenge landscape? (I pointed out in a recent August Post that a new E.H. booklet is now out, pulling together previous items).

Who is Tony Marsh?

Perhaps you have been using Twitter to discuss these things, but nothing has occurred on the Blog recently I think. My information librarian background makes me ask these questions: as Myris would say, back to the Primary Sources!

What would help us all to visualise the so - called periglacial stripes in the Avenue would be a three - dimensional computer - produced Model of this LIDAR mapwork with its very detailed contour lines. Perhaps this will be forthcoming.

BRIAN JOHN said...

Hi Tony -- over the years, lots of bits of original research have come to our notice pre-publication. We have our sources........

Seriously though, Chris brought this to my attention, and Tony M very kindly provided the image. I'll leave it to them to explain further if they wish.

ND Wiseman said...

Hi Tom

I don't think I've ever heard that the Stonehenge Avenue was the first to be built.
As a matter of fact, it's most likely to have been the last to be built.

Neil

Myris of Alexandria said...

It was discussed on britarch sandwiched between the anti-Janus of Kostas and van damn.
The stripes I think we're known in the fifties. I think Stone mentions them.
M

chris johnson said...

Tony, I came across the picture on the Britarch list Myris was referring to. There are interesting contributions but unfortunately a couple of trolls like to keep themselves as the centre of attention so I might not stick around.

I learned for example of a BBC program on new discoveries in the mesolithic and there is a very interesting contributor who tells about aboriginal ways.

As you perhaps remember, one of my puzzles is why some parts of the Mabinogion seem to recall a time when you call walk or at least wade to Ireland from Wales. The aborigines have stories about previous climatic episodes apparently - something to dig into when I have more time.

Sometimes you are kind enough to alert us to new discoveries and tv programs via this blog, which I appreciate. This is the only blog I check daily and where all contributors nowadays are worth reading.

Chris

TonyH said...

It should be possible to produce the 3 - dimensional model of the Avenue below the Heel Stone's so - called stripes, see my previous comment.

If this becomes available to view, it will be much easier for all of us to grasp the points being made as to exactly what the land surface and sub surface looks like, and what landscape formation processes have been at work over millennia.

We have a wonderful physical model for the LIDAR work done on the Bradford - on - Avon Hundred area, above the Bristol Avon, incorporating the plateau above the town where a prehistoric landscape has been revealed in fantastic detail. Go to "Bradford - on - Avon Museum: Ancient Landscapes".

TonyH said...

Regarding Myris's 22 Aug comment at 15.05, thought it might be worth briefly reminding folk what MPP'S's "Stonehenge" (2008) has to say about local amateur archaeologist "Jack" Stone (page 261, chapter 17, "Origin of the Bluestones").

"Back in the 1940's, Jack Stone had none of these fancy techniques [e.g. previously mentioned ground penetrating radar; LIDAR]. Field - walking, excavation and looking in holes in other people's gardens were the ways he searched for new sites. One of his interests was in tracking down the distribution of pieces of bluestone around the Stonehenge landscape."

It's worth checking out by reading further as to 'What Jack Stone Did Next', and what MPP & Colin Richards...and others, including Rob Ixer, went on to do regarding land to the NW of Stonehenge near or on The Cursus (pages 262-64).

TonyH said...

How did MPP, Mike Allen, and Charley French EARN their periglacial Stripes? Should they now be stripped of them, in a manner of speaking? Has it all been smoke and mirrors? What next??

Tom Flowers said...

Hi Neil, Hi Brian.
Sorry to take so long to get back to you both, but I have been immersed in the new book ‘The Stonehenge Landscape.’
I particularly like the way, near the end, where it tries to guide the reader away from new ideas and shut the book on them...
“It is therefore pointless to seek one over-arching ‘meaning’ for a monument such as Stonehenge, and any claim to have found such a meaning - to have ‘decoded’ or ‘solved’ Stonehenge - should be treated with suspicion.”
This is treating adults as children...The same as telling them not to talk to strange men.
There was only one hypothesis governing Stonehenge, lots of approaches to it - Yes - but only one hypothesis.
There is no other reason, but one, for connecting Stonehenge to a moon-aligned egg. And Pearson knows it! See therealstonehenge.com
This is what the book says about transport of the bluestones:
“The pillar-like form of many of the bluestones indicates that they are unlikely to have been moved by glacial action, and it is now established beyond reasonably doubt that they were brought from south Wales by human agency” (eg Parker Pearson 2012, 265-73).
There are several such ‘claimed positives’ in the book, perhaps I will get to them all later.
Regards
Tom

BRIAN JOHN said...

Tony, I have no idea where the "periglacial stripes" idea came from. I should have thought that any geomorphologist seeing these features for the first time, on the opening up of a new excavation pit, would have said "probably they are solutional rills." For some reason never enunciated, Mike and Charley did not say that but came up with another explanation. Maybe, if we wait long enough, we will get an explanation......

BRIAN JOHN said...
This comment has been removed by the author.
BRIAN JOHN said...

Tom

I disagree with you re this statement: "It is therefore pointless to seek one over-arching ‘meaning’ for a monument such as Stonehenge, and any claim to have found such a meaning - to have ‘decoded’ or ‘solved’ Stonehenge - should be treated with suspicion.” That sounds rather sensible to me......

But on this one: “The pillar-like form of many of the bluestones indicates that they are unlikely to have been moved by glacial action, and it is now established beyond reasonable doubt that they were brought from south Wales by human agency” (eg Parker Pearson 2012, 265-73)." The authors are clearly up the creek. Repeating a lie often enough does not make it true, and citing MPP as an authority on this matter is really rather strange. This is NOT established beyond reasonable doubt. Sure, SOME of the stones are pillar-shaped, but I would hazard a guess and say that the majority of them are not. I have dealt with this at length before.....

BRIAN JOHN said...

I got this message from Tony Marsh after he had problems with posting a comment directly to the site:

I tried to comment but failed on your website - something odd.
There was no need for you to be controversial by saying that maybe the alignment of the avenue is not significant.
It points to the ring centre
It v. likely was a processional route
It runs along a ridge and maybe bisected a grass(crop)mark in drought times that resembled the hair on a wet pig's back . . .
Some, maybe, would have noticed the alignment with the summer solstice sunrise and been in religious ecstasy over that. Surely there was never anyway any astronomical or lunar link?
The solstice alignment is remarkably good - one HAS to wonder . . .

Tony