The Gernos-fawr moraine

Well now -- this is as fine a moraine as I have seen in a long time.  Its at Gernos-fawr, near the headwaters of the Gwaun River, at an altitude of 240m.  A very distinct mound in the middle of the valley, littered with boulders of all shapes and sizes, but mostly faceted and sub-rounded -- as one would expect with a deposit made largely of glacially-transported material.

Why haven't I spotted it before? The reason is that this hillock has been previously covered with gorse bushes -- and it is quite recently that the farmer / smallholder here has had the pigs in to clear it, followed by sheep, geese and chickens.  So all is now revealed......

 The Gernos-fawr moraine is at the black spot, bottom right of the image. Click to enlarge

What is the significance of this find?  Really, I haven't got a clue.  According to all my predispositions, there shouldn't be a moraine here at all, since it is on the south side of the Gwaun Channel, about 2 km distant from the hump or highest point on the valley floor.  I assume that it is Devensian in age -- so could it have been built at a glacier terminus following ice movement across the Carningli massif and across the Gwaun Channel?  That's possible, since I have speculated many times before on Carningli being completely covered by ice at the Devensian maximum.  Here is one of my earlier maps, with Gernos-fawr marked on it:

 As we can see, Gernos-fawr is very close to this suggested ice limit, given than an ice edge never is straight -- but tends to mould itself to the contours, fingering up valleys and leaving ridges ice-free.
So far so good.  Now for something I have just discovered,  having looked rather carefully at the satellite image above (the second image on this post.)  Click to enlarge, and then have a look at the area of big fields NNE of Gelli-fawr and the area to the SW of Gernos-fawr.  Do you see the slight traces of elongated curving ridges?  I have a feeling that these might be slight traces of morainic ridges, related to a lowering (retreating) ice edge.  This is rather exciting -- I must go and check them out in the field, while bearing in mind that they might be structural benches.

You saw it here first, folks.  I'm on the case.  Watch this space.....

New OSL dates for North Somerset sediments

Six new dates have been obtained from sediments in the Gordano Valley, North Somerset, as part of a research project by Anne Bridle from West of England University in Bristol.

This area is well known for the presence of glacial and related deposits, proving that the ice of the Irish Sea Glacier extended into North Somerset on at least one occasion and possibly more.

In a brief note ("Optical Ages of a Pleistocene sequence in the Gordano Valley, North Somerset, UK"  Quaternary Newsletter Vol 129, Feb 2013, p 72) the researcher says that samples were taken from a sequence of sands, gravels and "clay drift" beneath the recent peat layer.  The "clay drift" may be till, but the author doesn't comment on this.  The dated samples all come from the sands and gravels, and they range somewhat erratically between 91,000 and 62,000 BP -- which places all of them into the Early Devensian and possibly the preceding interglacial.  It's a pity that the OSL technique is the only one used here, since all of the new methods of dating non-organic materials really need checks from other techniques so that systematic errors can be eliminated.  So we don't know as yet whether these dates can be taken at face value.

But if, for the moment, we accept that they are reliable, this means that the till (?) at the base of the sequence cannot be Devensian, and must therefore be Anglian -- as we have suggested on this blog many times before.

So although there may well have been small ice caps on Dartmoor, Exmoor, Mendip and other upland areas of the South-West, it does not look, according to current evidence, as if the Devensian Irish Sea Ice Sheet transgressed across the Somerset coast........

Dartmoor Glaciation disputed

Just in case there is anybody out there who thinks that archaeology is the only discipline within which assorted tribes slug it out on their battles for supremacy, rest assured that the same thing goes on within geomorphology too.  In a series of posts in June last year I reported on the new paper by Prof David Evans and others in which they presented the evidence of glaciation on Dartmoor:

http://brian-mountainman.blogspot.co.uk/2012/06/dartmoor-ice-cap.html

I found this evidence very persuasive, especially since it was backed up by modelling work and had a very strong internal consistency about it.  Furthermore, the guys responsible for that paper know their glaciers pretty well, having worked all over the world.

Now a senior geomorphologist named Allan Straw has thrown a spanner into the works, with a short paper entitled "Dartmoor Glaciation -- Fact of Fiction?" and published in Quaternary Newsletter, Vol 129, Feb 2013, pp 46-51.  He runs through a number of lines of evidence, defending in each case the old and traditional view that almost everything on Dartmoor can be explained by reference to a very long history of periglacial action combined with slope processes. 

What should one make of the new spat?  Well, it's all innocent fun -- another case of bright young things coming up with a radical new theory and a senior academic defending the status quo, to which he has no doubt held a lifelong allegiance.  That having been said, I don't find Allan Straw's defence of the ancient tradition very convincing -- it presents no new evidence, and simply seems to be a demonstration of scepticism,  suggesting that certain named features MIGHT just be periglacial after all, and not glacial.....

It will be interesting to see how David Evans and his colleagues respond to this criticism, as they undoubtedly will.....

World of Ice slideshow on YouTube

I have put together some of my favourite slide from the polar regions and the high mountains and made a short YouTube film.  The music is "Oceana" by Golijov -- enjoy!!

http://youtu.be/xTBVp6Vz3Lw

Here is an embedded version:

New Stonehenge book

Thanks to Jon Morris for sending a review copy of this book, which is now available both in printed and Kindle formats.  Below I have printed Jon's blurb for the book.  Having looked through it, I have to say that it is not exactly my sort of Stonehenge book -- but part of a long tradition of tomes (such as those of Robin Heath) concentrating on the mathematics, engineering and astronomy of the monument.  The central thesis is that the monument -- at least in  some of its idealized reconstructions -- was a model of a geocentric universe, used with poles, ropes and mirrors as a sort of planetarium for educational, research and entertainment purposes by rather a sophisticated society that must have had time on its hands.

Jon clearly subscribes to the "ancient wisdom" school of thought -- believing in a group of highly skilled and numerate individuals capable of conducting sophisticated observations and even controlled experiments related to star movements and solar movements from month to month and season to season.

I have major problems with this approach, for a number of reasons.

1.  I find it hard to know just how accurate all the stone settings and alignments really are.  Jon tells us that there is extraordinary accuracy involved here, but I am not so sure, and it appears that many archaeologists these days accept that there are too many "almosts" and "approximates" for comfort -- with authors like Jon referring over and again to theoretical or "desired" stone locations rather than actual surveyed locations.

2. I find it hard to believe that those who were responsible for the stone settings at Stonehenge had access to the technology capable of manufacturing and engineering arrays of highly polished and shaped solar reflectors located so as to create an artificial sun positioned on a moving system of timber arms........

3.  Why would these brilliant engineers want to do all of this anyway?  You don't need complicated gadgets and displays to tell you that the sun goes round in the sky, and up and down, and that the seasons follow one another in sequence.  The growing season comes, and goes, and comes again.  It all seems far too frivolous to me -- it provides Jon and others lots of innocent amusement, but in the Neolithic I don't see any evidence from anywhere that the inhabitants of Salisbury Plain would have been interested in things that might nowadays have occupied the minds of higher-level mathematics and engineering students.  Research and entertainment were, I assume, rather low on the list of priorities, when there was the little matter of surviving to cope with.

4.  I found the section on "the size of the world" very unconvincing, and I thought the arguments and "evidence" were highly selective and forced into a predetermined hypothesis.  Then I found the section of folklore even less convincing.......

So there 'tis then.  I'm nonetheless happy to give some space to the book, and to celebrate the rich diversity of views which keeps us all occupied and entertained!

http://www.amazon.co.uk/Stonehenge-Solving-Neolithic-Universe-ebook/dp/B00A25VWYG#reader_B00A25VWYG


The book blurb:

Current opinion of Neolithic times imposes medieval roles on men and women: Women as chattels, men as warriors and monuments as places of worship and human sacrifice. But what if such a patriarchal society did not exist before history was recorded?

This fully illustrated e-book, by a Fellow of two engineering institutions, puts forward a detailed and fully developed alternative interpretation for Stonehenge based on recent research into renewable energy: It shows how its plan layout is the same as an idealized geocentric (fixed world) description of the Universe; its inner stone monument is shown to be capable of creating a spectacular visual description of a the sun's movement around a fixed world.

Part 2 shows examples of where that early knowledge of the Universe could have been obtained. It also shows that, in all the locations needed, the monuments of that period appear to fit that which would be required.

Part 3 is about how the monuments would be perceived: It shows how mythological and Arthurian references all appear to fit this explanation of Stonehenge and other monuments. This offers an alternative explanation for the Grail and the Four Treasures of.the Tuatha Dé Danann.

Part 4 looks at the most recent evidence published in 2012 and part 5 summarizes the possibilities.

Good progress on new Stonehenge Visitor Centre

Stonehenge transformation work well on schedule
Tuesday 19th February 2013 in News

http://www.wiltshiretimes.co.uk/news/10237112.Stonehenge_transformation_work_well_on_schedule/

Work on the Stonehenge site is due to be completed by the end of this year
Work to transform Stonehenge, which officially started on site in July last year, is progressing well.
This year, the centenary of the 1913 Ancient Monuments Act, will culminate in the opening of English Heritage’s new Stonehenge exhibition galleries and visitor centre at the end of the year.
Building work is currently taking shape at Airman’s Corner, 1.5 miles to the west and out of view of the stones, where the new galleries and facilities will be located.
The sensitively designed building will comprise two “pods” which will house museum-quality exhibitions, a spacious café with indoor and outdoor seating, a bigger shop and dedicated education space.
Main contractor Vinci Construction is about to erect a ’bird-cage’ scaffold which will be used to install the undulating canopy roof, a distinctive feature of the building’s design, while a visitor car park and coach park, with capacity for 500 and 30 vehicles respectively, have been laid out and are clearly visible.
Precious objects on loan from the Wiltshire Heritage Museum in Devizes and the Salisbury and South Wiltshire Museum are currently being conserved by English Heritage staff ready for display.
They will form the centrepiece of the permanent exhibition at the new building, helping to tell the story of Stonehenge in vivid detail.
Next month volunteers will help with an archaeological experiment at Old Sarum Castle near Salisbury where prototypes of Neolithic houses excavated at Durrington Walls will be built. The lessons learned from this experiment will inform the reconstruction of three Neolithic houses at the outdoor gallery of the new visitor centre in Spring 2014, offering visitors a glimpse of the lives of prehistoric people.
The A344 road between Stonehenge Bottom and Byway 12 will be closed at the end of June, once the new roundabout at Airman’s Corner is operational. Work will follow to remove the fences along this section of road and the road surface itself will be removed and grassed over.
No part of the Stonehenge operation will close while the works are being carried out, and the switchover to the new visitor centre will happen overnight. Until then, access to the existing Stonehenge car park will continue along the A344 but from the west via the A360 and Airman’s Corner.
The date of the opening at the end of 2013 will be announced later in the year.

Dating the Dartmoor Tors

This is an interesting paper, just published. I haven't had a chance to read the full thing yet, but it appears from the abstract that the cosmogenic dates for the Dartmoor tor surfaces are remarkably young, clustering in the period 36,000 - 50,000 years BP.  In other words, the rock surfaces were first exposed during the long period of periglacial conditions before the build-up of the short-lived Dartmoor Ice Cap which we have discussed earlier.

I still have a healthy scepticism for cosmogenic dates, since there are many things that can influence them and lead to false ages, but I'll reserve judgment until I have looked over the paper properly.

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





The granite tors of Dartmoor, Southwest England: rapid and recent emergence revealed by Late Pleistocene cosmogenic apparent exposure ages
Gunnell, Yanni; Jarman, David; Braucher, Régis; Calvet, Marc; Delmas, Magali; Leanni, Laetitia; Bourlès, Didier; Arnold, Maurice; Aumaître, Georges; Keddaouche, Karim
Quaternary Science Reviews, Volume 61, p. 62-76.

ABSTRACT
Dartmoor, in SW England, is a classic periglaciated granite upland adorned with a population of over 150 tors. The origin of the tors has been controversial, but their emergence by differentiation after stripping of regolith during Pleistocene cold phases is accepted. However, their actual age has been unknown, with possible scenarios ranging from preservation since the early Middle Pleistocene to relatively short-lived landforms in a maritime climate with high denudation rates. The latter is now supported by 32 cosmogenic surface exposure dates from 28 tors across the whole upland. The distribution of apparent ¹⁰Be ages peaks strongly in the Middle Devensian (36-50 ka), which with corrections for weathering and limited ice shielding could be interpreted as Early Devensian. These ages are much younger than those found for three glacially unmodified Cairngorms tors, and somewhat younger even than glacially modified Cairngorms tors. The dates show little spatial variation. Although an ice cap has now been modelled in the heart of northern Dartmoor, tors here are of median age, suggesting that ice cover sufficient to shield tors from incoming radiation was of short duration. The few younger tor ages support the idea of continuing landform instability across the landscape, with weathering flakes redeveloping soon after inferred loss of top pillows by gelifraction or gravitational toppling. The few older tor ages have no systematic explanation, and may indicate inheritance from an earlier cycle of bedrock near-exposure. Since most tors are modest in height (typically 2-5 m), volumetrically insignificant, and often in advanced stages of disintegration, the general impression is that they are evanescent features, which emerge and quickly disappear during every Pleistocene climatic downturn. Tor populations may thus flicker across the landscape rather randomly over the Quaternary. The remarkably consistent age of the present tor population could be associated with a stripping event at the start of the Devensian, but fuller analysis must await closer controls on tor denudation rates in different climatic phases, and on ice cover extent and duration. These results only date extant tor surfaces, not the landscape, but as the best available erosion pins they have evident value in exploring theories of the evolution of Dartmoor during the Quaternary. 

The work of ice -- dismiss at your peril!

 Grundvigskirken, East Greenland (Photo:  Troels Jacobsen.)

I was talking to somebody at a party the other day.  He said he visited the MPP dig at Rhosyfelin during the summer, and embarked upon a little conversation with the boss himself.  He had the temerity to mention the possibility that the bluestones at Stonehenge might have been carried by ice, only to receive the rebuff: "Forget it.  That theory has been comprehensively dismissed."

If I had been there I think I might have pressed a bit, and asked (ever so politely)  "By whom?  When? And on what basis?"  But unfortunately (or fortunately) I was elsewhere at the time.

But it does make me angry that a senior academic who clearly knows nothing about glaciation and the work of ice should pontificate in this fashion and should appear to have a closed mind on the matter, simply because it is inconvenient to the fantasy world which he has created around Stonehenge and Rhosyfelin. 

Anyway, for those who do not know what to think,  here is another little reminder of what ice is capable of.  Grundvigskirken again, in the inner reaches of Scoresbysund, East Greenland.  And just round the corner is Nordvestfjord, the biggest fjord in the world, in which the ice has cut into the ancient landscape so deeply that one can measure 11,000 feet from plateau surface to fjord bottom.

Professor MPP, you underestimate the capabilities of glacier ice at your peril!

Paying for that mighty project

Spotted by one of our eagle-eyed observers.  Just in case anybody wondered how English Heritage plans to finance its wondrous Stonehenge Visitor Centre in these straightened times........