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Thursday, 1 December 2016

The weird obsession with periglacial stripes

 Image: Adam Stanford

There's a new post on Mike Pitts's blog called Digging Deeper.

https://mikepitts.wordpress.com/2016/11/

In it, he refers to the strange idea (emanating from MPP and his colleagues) that the undulations within the confines of the Stonehenge Avenue are "periglacial stripes" and that the orientation of these stripes coincident with the solstice axis is responsible for the placing of Stonehenge where it is.  I have always thought of that as a crazy idea, and Mike Pitts seems to think so too.  Mike has some nice illustrations in his piece, and displays a proper degree of scepticism, but he still seems to accept the periglacial origin for these features, and also for other small rills which are now visible at the new Larkhill excavation.

There is nothing at Larkhill either to suggest a "periglacial" role in the formation of these rills, and the perfectly obvious explanation for all of them, as we have said over and again on this blog, is that they are simply solutional rills created by water moving downslope, possibly assisted by permafrost (which has the effect of reducing the infiltration of water into the ground). 

It's very confusing to refer to patterned ground features like these as "periglacial" since there is no evidence at all of patterned ground processes at play, involving the lateral movement of particles into stripes of larger fragment sizes separated by stripes of fines.

Maybe some people just like the word "periglacial" because it sounds mysterious and scientific?

8 comments:

Alex Gee said...

AG says; I share your frustration Brian!

There is a significant body of literature on the effects of periglacial climate and permafrost on chalk bedrock in Southern England!

This overwhelming demonstrates that the processes involved cause mainly bedrock brecciation and the formation of involutions etc at the surface. NOT the formation of rills!

The literature on Karstic processes in Southern England demonstrates that the formation of rills is solely the province of chemical dissolution.

Rather than write reams of nonsense about "how were the mystical stripes formed"? why don't the archies just read a few papers on the subject? or better still consult the people who wrote them?

If they did so they may make the same observation that I did? namely "Don't all those photos from chalk quarries showing the geologically recorded remains (involutions and breccia) of the Devensian permafrost active layer, look exactly like Atkinson's B/W photos of his excavations of the stumpholes at Stonehenge"?

Cheers

Alex







AG said...

Brian: As an aside, I could send you two or three of the relevant papers if you wish?

Cheers
Alex

BRIAN JOHN said...

Feel free, Alex -- I would appreciate that. If you have PDFs, that's fine.....

You make a perfectly sound point re the nature of the regolith / solid rock interface. Could the honeycomb of intersecting "sockets" at Stonehenge simply represent a natural phenomenon -- namely a highly irregular bedrock surface created by solution processes? We see this on the chalk cliffs of the southern England coast. A question worth asking.......

TonyH said...

Crikey, Alex and Brian! Sounds like you could be onto a winner here...... which may be a "loser" for all "experts" on the history of Stonehenge through the excavations of the 20th Century! No wonder they don't like talking to most researchers from other relevant Earth History specialisms!

TonyH said...

The thing is, of course, that since Victorian times Stonehenge has been the virtually exclusive province of antiquaries and then archaeologists. Earth Scientists, with the honourable exception of one of two notable geologists like Dr Ixer, have hardly had a look in, except when explicitly invited e.g. as part of the 21st Century Stonehenge Riverside Project. Stonehenge consequently became a Laboratory for those trained in archaeology...........with Joe Public invited to listen to or watch their interpretations of all things beneath the surface. Joe Public, when presented with these indisputable "facts", went along with their interpretations, hook, line and sinker.

BRIAN JOHN said...

Just a reminder of a relevant post from August, if we are contemplating the irregularity of the bedrock surface under the regolith:
http://brian-mountainman.blogspot.co.uk/2016/08/extraction-pits-solution-hollows-post.html

AG said...

Pdfs sent.

Neil Wiseman said...

Gents & Other Vagabonds,

While making no claim to the provenance, likelihood, or even definition of the term: "Periglacial Stripes", there is another facet of Mike's blog-post in which I found particular interest.
This involves Tim Darvill's send-up that at least some of those stripes are wagon-tracks.

Like others who dwell in the lofty, ethereal atmospherics of Stonehenge All-Knowledge, with a smirking shrug I was quick to dismiss this somewhat left-field assertion from an otherwise noted and respected researcher.

Be that as it may, my interest was piqued, so with the intent of assembling iron-clad, scathing commentary to counter the ridiculous notion, I did a little research to arm myself with irrefutable proof to the contrary.

My shuffling, candle-lit foray into the dim and dusty Vault of Forgotten Secrets produced the series of 2nd Lt. Phillip Sharpe's six balloon pictures of Stonehenge, taken in 1906. These aerials show the site overhead and from the oblique, and one of them is of great interest.

Taken from the SW, it includes the stones and henge while looking up the Avenue where, lo and behold, a path on its west side seems to come down, cross the future A344 road, and intersect another, unequivocal cart-track which skirts the stones and merges into the west-side split of the old Byway-12.
This cartway looks to have once been in regular use, as ruts are obvious and chalk partially exposed.
(This approach was apparently abandoned when Lord Antrobus put up the fence along the east side of the byway four years before, thereby blocking access and allowing grass to partially return. It also solves another mystery, but that's a different story ...)

In review of other images, including LiDAR, this track punches through the Avenue at the Elbow and makes its way up to either Strangeway or Countess, east of Larkhill, west of Durrington.
From those farms, if I wanted to get to markets in Normanton or points southwest, I would take the short-cut straight shot down the Stonehenge Avenue, avoiding the longer dog-leg of Countess Road or Byway-12.

MPP's excavation of the Upper Avenue in 2007, and Adam's subsequent overhead picture, shows the same location from the opposite angle, ie: looking SW to the Heelstone.
There definitely Are stripes within that corridor, but over on the west side, near the bank, are those narrow, dual, evenly-spaced track-like marks which speak to long-term use.

So then, having fallen to earth from my lofty tower with a loud, unpublished splat, I submit that both stripes and wagon-tracks are legit.

Neil