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Monday, 12 November 2018

The bluestone quarries -- the best hoax since Piltdown Man?

Rhosyfelin.  Does anybody else see a loading platform and a revetment here?  No?  Neither do I.

Carn Goedog.  Does anybody else see a stone-filled ditch, a platform and a pillar extraction point when they look closely?  No?  Neither do I.

Rhosyfelin.  Does anybody else see the "exact extraction point" from which a bluestone monolith pillar has been extracted?  No?  Neither do I.

Carn Goedog.  Does anybody else see evidence of a Neolithic quarry from which bluestone monoliths have been extracted?  No?  Neither do I.


Rhosyfelin.  Does anybody else see a quarrying forecourt and working surface here?  
No?  Neither do I.

The Art of the Scientific Hoax

I have done various posts on hoaxes before, including the following:

https://brian-mountainman.blogspot.com/2018/04/the-bluestone-quarries-great.html

Anyway, having observed the antics of various archaeologists (and geologists) over the last eight years, I am now completely convinced that the claimed “discovery” of Neolithic bluestone quarries in Wales is the most imaginative and professional hoax since Charles Dawson “discovered” Piltdown Man in 1912. (1)  What is possibly most impressive about it is that it has been built up systematically now over a period of eight years without any of the conspirators spilling the beans.........

Charles Dawson (sitting) at the site of his "earth-shattering" discovery........


It's a pity that scientific hoaxes have gone out of fashion, since they cause much embarrassment to the experts who are fooled by them and much innocent amusement for everybody else. Mind you, they don't do much for the reputations of the perpetrators -- although, if you are lucky, like Charles Dawson, you might be dead before you get rumbled.

As followers of this blog will know, year after year I have conducted — in all seriousness — a forensic examination of all of the evidence placed into the public domain by the archaeologists who claim that there are bluestone monolith quarries at Rhosyfelin and Carn Goedog in the Preseli uplands of Pembrokeshire; and time and again I find that the evidence just does not withstand even superficial scrutiny (2). So I'm sure that the archaeologists, led by Professor Mike Parker Pearson of University College London, have pulled a fast one and have joyfully fooled the media, the public and a large part of the archaeological establishment.

For a scientific hoax to be successful, it requires three preconditions:

1. A gullible public predisposed to believe in “new discoveries” — in this case, stories about the great skills of our prehistoric ancestors and the meaning of Stonehenge.

2. A colourful and swashbuckling lead character who has a respectable past and a strong media presence.

3. A body of “evidence” cited in support of the hoax which cannot be checked or replicated by anybody else.

All three preconditions are amply fulfilled in this case. In these days of alternative facts and false news, almost anything will grab the attention of the public.  The mere use of the word "Stonehenge" in a press release guarantees wide media coverage.  MPP is a popular figure who has been called the “Indiana Jones” of British archaeology, with a reputation for an endless stream of controversial theories. As far as I am aware, there was no independent scrutiny or peer review of the dig sites at Rhosyfelin and Carn Goedog while MPP and his team were at work between 2011 and 2016.   And the excavations have now been filled in, so that nobody can go back to them to check the cited “evidence”.  Wonderful!  That's a perfect scenario for a successful hoax……….

There has been extensive media coverage of the “bluestone quarries” since 2011, and this has ensured a considerable flow of research funding to finance eight digging seasons at the “quarrying” sites and elsewhere, as the archaeologists claim to be hunting for “proto-Stonehenge” in the North Pembrokeshire landscape.  Interestingly enough, the breathless and uncritical coverage has come not just in the tabloid press but also in popular archaeological and historical magazines.  Even science journals which -- presumably -- have some respect for the scientific method, have been swept along in the torrent of fake news coming from the digging team and their university press offices.

https://www.manchester.ac.uk/discover/news/stonehenge-bluestone-quarries-confirmed-140-miles-away-in-wales/
https://www.telegraph.co.uk/science/2016/06/05/original-stonehenge-was-dismantled-in-wales-and-moved-to-wiltshi/
https://www.dailymail.co.uk/sciencetech/article-6018799/Ancient-WELSHMEN-helped-build-Stonehenge-5-000-years-ago-using-vast-bluestones.html
https://www.archaeology.org/issues/208-1603/trenches/4162-trenches-wales-stonehenge-bluestones
https://www.pourlascience.fr/sd/archeologie/lorigine-de-certaines-pierres-de-stonehenge-identifiee-au-pays-de-galle-12225.php

But clues as to what was going on were picked up at an early stage. The archaeologists who started digging at Rhosyfelin in 2011 announced before they broke the turf that they were investigating a quarry — which raised a few eyebrows. (Scientists do not normally announce their results before their research has started…..) At all stages of the dig, when I examined the open excavations in the company of other geologists and geomorphologists, we became more and more certain that all of the claimed “quarrying” or engineering features were entirely natural. Three of us published two peer-reviewed papers in 2015 containing our findings, but the archaeologists refused to acknowledge the existence of the papers, and even now, three years later, they will not admit that there is a dispute going on (3).  This is not just bad manners; it is scientific malpractice.

It gets worse.  After eight years of digging, not a single field report has been published. There have only been two reviewed journal articles, the first described by a senior academic as “one of the worst papers I have ever read” and the second one equally suspect (4).  The radiocarbon dating evidence from the two excavation sites does nothing to support the idea of quarrying, and has indeed been claimed to comprehensively falsify the quarrying hypothesis (5). No earth scientists have been systematically involved on-site in the annual excavations, which means that no serious questions have been asked when features have been interpreted as man-made. There have been no “control digs” at similar sites which migh demonstrate that the “quarrying" features are distinct or unique. And finally, not one of the many sites examined thus far for traces of “proto-Stonehenge” has proved to have anything to do with the iconic monument on Salisbury Plain (6). At every setback, the archaeologists have refused to back off,  have simply made their story more elaborate, and announced their next anticipated big discovery………..

So do the archaeologists still have any credibility? No.  Has the hoax finally run out of steam? Yes.

Here is a suggestion to the six senior members of the “bluestone quarries” project.  You've been rumbled.  Come clean, and admit that you have been enjoying a jolly prank with a serious intent in the background — namely to demonstrate how easy it is to promote a hypothesis that is underpinned by zero evidence.  Job done.  You should now, with smiles on your faces,  remind the public and the media that they should not necessarily believe things simply because they are repeated over and again, with apparent conviction, by senior academics.



NOTES

(1)
 Charles Dawson’s “Piltdown Man” hoax, perpetrated in 1912, is one of the most famous scientific hoaxes of all time. Dawson (with the aid of other persons unknown) fabricated bits of two human skulls and claimed that he had discovered, near the village of Piltdown, the “missing link” between apes and human beings. There were concerns about his “discoveries” but the hoax was not proven until 1953, many years after Dawson’s death in 1916.

(2)
https://www.academia.edu/19788792/Quaternary_Events_at_Craig_Rhosyfelin_Pembrokeshire

https://www.academia.edu/19788912/Observations_on_the_supposed_Neolithic_Bluestone_Quarry_at_Craig_Rhosyfelin_Pembrokeshire

“The Stonehenge Bluestones”, 2018, Greencroft Books, 256 pp. ISBN: 978-0905559-94-0
http://www.brianjohn.co.uk/the-new-book.html

(3)
Parker Pearson, M., Pollard, J., Richards, C. and Welham, K., 2017. The origins of Stonehenge: on the track of the bluestones. Archaeology International, 20, pp.52–57. DOI: http://doi.org/10.5334/ai.353
(4)
 Mike Parker Pearson, Richard Bevins, Rob Ixer, Joshua Pollard, Colin Richards, Kate Welham, Ben Chan, Kevan Edinborough, Derek Hamilton, Richard Macphail, Duncan Schlee, Jean-Luc Schwenninger, Ellen Simmons and Martin Smith (2015). Craig Rhos-y-felin: a Welsh bluestone megalith quarry for Stonehenge. Antiquity, 89 (348) (Dec 2015), pp 1331-1352.

"Craig Rhos-y-felin: a Welsh bluestone megalith quarry for Stonehenge", by Mike Parker Pearson, Richard Bevins, Rob Ixer, Joshua Pollard, Colin Richards, Kate Welham, Ben Chan, Kevan Edinborough, Derek Hamilton, Richard Macphail, Duncan Schlee, Jean-Luc Schwenninger, Ellen Simmons, Martin Smith
Antiquity, Volume 89, Issue 348, December 2015
https://eprints.soton.ac.uk/421631/1/Megalith_quarries_Antiquity_REVISED.pdf

(5)

(6)





Friday, 9 November 2018

CA continues its quaint quarrying promotion campaign

The so-called bluestone quarries "in focus",  according to Current Archaeology.  I thought that magnifying glasses were supposed to be used for close scrutiny, and for bringing clarity?  Instead, what we get is sychophantic and shallow journalism, no scrutiny, and most definitely no enlightenment......


Thanks to Tony and David for drawing my attention to this one:

"Moving Monoliths: new revelations from the Preseli bluestone quarries". Current Archaeology, No 345, Dec 2018, pp 52 -- 55.

New?  This is all very surprising, since there has been no new work at either Carn Goedog or Rhosyfelin, and the last publication to mention the sites was almost a year ago:

Parker Pearson, M., Pollard, J., Richards, C. and Welham, K., 2017. The origins of Stonehenge: on the track of the bluestones. Archaeology International, 20, pp.52–57. DOI: http://doi.org/10.5334/ai.353
https://brian-mountainman.blogspot.co.uk/2016/01/parker-pearson-et-al-on-carn-goedog.html

It is a sad state of affairs when a journal insists on flagging up "new revelations" when there is really nothing of any interest out there. Having now had a chance of looking at the article, it's clear that whoever wrote it has been conned.  He or she simply regurgitates material that is at least three years old, which has no more substance to it now than it did in 2015.  The author refers to all sorts of things that are supposedly "remarkable", including the "remarkable precision" of the Bevins / Ixer provenancing of individual stones to "specific rock faces."   That is wrong, as the author must know if he/she had bothered to read the literature properly. Then there is reference to "clear traces of Neolithic quarrying" -- with no mention of the fact that this is hotly disputed, with others (including myself) seeing no such traces.  The radiocarbon dating evidence, which by any independent analysis falsifies the quarrying hypothesis at Rhosyfelin, is portrayed as giving precise dates for quarrying activity.  "New revelations about how the stones were extracted and transported from the quarry sites are still emerging....."  Sorry, but there are no new revelations.  False news and sloppy journalism.

On and on it goes, with the author faithfully repeating whatever he / she has been told by MPP and his team.  It's all here -- the usual stuff about platforms, loading bays, trackways, dry stone walls and so forth........  As I have said before on this blog, this sort of stuff is typical of MPP and his team; we --  the gullible readers -- have no opportunity to see measured sections or site descriptions or to scrutinise this old-fashioned thing called  EVIDENCE.  What we get instead is a string of unsupported assertions and fantasies.  As I have said before, when I examined both of these sites I could see no evidence in support of any of these features, and had to conclude that they were all products of a desperate hunt for something of significance.  We don't even get to see the stratigraphic context of a "new" radiocarbon dated sample.  We are just expected to accept that it is important.

What is most entertaining in this article is the use of several photographs from the two digs at Rhosyfelin and Carn Goedog, purporting to demonstrate the existence of the "engineering features" which are lovingly referred to in the captions.  That was not a smart idea.  I defy any reader of the magazine to say, with hand on heart, that they can see anything in the images other than a jumble of rocks and sediments, arranged by nature without any human intervention at all.

Much is made of the discovery of something that might be a Neolithic end-scraper --  but the supposition that this might have had something to do with quarrying is nonsensical.  The reference to "a large, level platform" at Carn Goedog is frankly ridiculous -- on the photos it is neither large nor level, and when I examined in it reality, when the excavation pit was still open, I simply saw a jumble of large rocks with many different sloping surfaces which could never have facilitated the sliding and removal of pillars or anything else.

The latter part of the article consists of a string of yet more speculations and fantasies, bringing in proto-Stonehenge and Bluestonehenge for good measure.  Those are best forgotten about -- the evidence -- such as it is -- is years out of date.  On the final page of the article, there is a summary of what MPP et al wrote in the 2017 article:

Just beyond the edge of the platform we found an 11 m-long, 3 m-wide ditch. Dug to a depth of 0.4 m, its upcast was deposited on the side away from the outcrop and the ditch was then filled with large stones, creating a permanent barrier across which no monolith could be transported. The latest radiocarbon date on charcoal from this ditch indicates that it was filled-in around or after 3020–2880 BC. ..................      In summary, Carn Goedog’s main period of monolith extraction was slightly later than at Craig Rhos-y-felin, in the two or three centuries before 3000 BC. The same method was used of lowering monoliths onto a level platform, in this case built largely of large flat slabs with sediment in between them, sitting on top of the Neolithic ground surface. Unlike Craig Rhos-y-felin, no hollow way was formed by the hauling-away of monoliths, presumably because the hard ground and tough grass cover on this elevated hillside were not eroded by moving stones over the surface. The construction of a stone-filled ditch (the date of which coincides with Stage 1 at Stonehenge) as a barrier to cut off access to bluestone pillars from the outcrop, is intriguing. It may have served to prevent removal of any more of these important stones.


It's saddening to see that yet again CA is allowing itself to be a free promotional vehicle for something that just does not make any sense.  Just think about it for a moment -- why on earth would the  Carn Goedog quarrymen (just for fun, let's assume they actually existed) want to dig an 11m long ditch and fill it with big stones, just to stop people taking any more monoliths away from Carn Goedog?  When I looked, I saw no ditch, no spoil heap and no "fill" of large stones.  We are just told that they existed, and are expected to believe.  There is no evidence that the spotted dolerite from here (or anywhere else) was revered or special in any way, and if anybody had wanted to collect spotted dolerite monoliths they could have taken them from anywhere on other parts of the tor, or from the abundant assemblage of elongated erratic stones littering the local landscape.  This really is the storytelling obsession take to the extremes of absurdity.

I have seen a number of "junk science" articles in Current Archaeology before -- but I think this one really does take the biscuit.

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

NOTE

Given the fact that Mike Parker Pearson announced, about a year ago, that it was his intention to discover a giant stone circle -- proto-Stonehenge -- at Waun Mawn in September 2018, I am 100% convinced that the editor of CA set aside space in the December 2018 issue of the mag for a huge "breaking news" article.  When it transpired in September that there was nothing of any great importance at Waun Mawn, the editor was forced to fill the vacuum with this hotch-potch of old news, dressed up as something new and exciting.  Others might agree with me that it is more exciting to sit in front of a blank wall, watching paint as it dries......

Confucius he say:  be careful what you wish for.

Was Stonehenge an art installation?




Following our discussion on whether Stonehenge was a folly -- and whether I was serious in suggesting that in a BBC interview -- here is another interesting twist.

There is due to be a conference next February between artists and archaeologists (I think it would be more useful if they were to have one between scientists and archaeologists, but that's another matter......)

Let's go back a bit:
https://brian-mountainman.blogspot.com/2010/09/more-on-stonehenge-folly.html

This is from another post in 2010:

Been engaging in a good debate on the Modern Antiquarian Forum, and thought I might share this post:
I have tried not to enter the discussion on WHAT STONEHENGE WAS FOR, but it's appealing to think of it as a puzzle, or an enigma, or a riddle, or even a folly. Maybe the builders themselves didn't know what it was for -- and there was just a powerful ruling clan who wanted to build something wacky as part of its attempt to establish its power base and to try out building techniques? Maybe they were VERY clever and knew that once it was built or partly built, for thousands of years thereafter people would expend vast amounts of energy and brain power trying to work out what the hell was going on...... and in the process invest the builders with spiritual, mathematical, astronomical and organizational skills that they never actually had. Brilliant!

Well, follies are generally built by eccentric people as a means of self-glorification. They have to have the cash and labour resources to do the job, and some handy land available, but otherwise (apart from the planning system) there's nothing much to prevent them from giving expression to their fantasies. Another feature about follies is that they are often not finished, because cash runs out, or the locals get upset about all this self-aggrandizement, and refuse to cooperate by withdrawing their labour or in other forms of sabotage. Stonehenge fits the bill precisely!

Anyway, some people have problems with the idea that Stonehenge might not have had either a practical or a ritual purpose.  There is some quite suggestive evidence to support the idea that Stonehenge was a folly, built by a power-mad cheiftain for self-glorification or else for the purpose of confusing future generations........

To repeat -- more or less -- what I said the other day:

1. Nobody can agree what Stonehenge is actually FOR. So it's an enigma -- and the whole point of creating a folly is that it should be enigmatic. Whoever had the cunning plan to build it, it obviously worked.

2. The signs are that it was never properly designed.  All that messing around with stone settings etc. Things that tend not to get finished are generally more frivolous than things that have a very serious intent -- like palaces and cathedrals etc.

3.  I read into the structure that the resources were never there to finish it -- either manpower resources or stone availability -- and that there was no clear economic imperative.

4. There was nothing like it before or after. That means it was an aberration, or a one-off. That signals folly to me.

5. All societies have their eccentrics and their peacocks who just want to show off.  It would be strange if Salisbury Plain had no prehistoric follies on it. 

In the context of the advance publicity for this artist/archaeologist symposium, Chris Catling has said
‘I think archaeologists are beginning to understand that the past cannot be interpreted solely in terms of practicalities: we will not fully enter the minds of our ancestors until we appreciate that the artistic impulse is evident in a Neolithic polished axe and an Iron Age hillfort, and that artists have in the past been the innovators, leading humans into new areas of experience’.

He is not exactly saying that "installations" like Stonehenge are not necessarily "functional" or utilitarian, and he is not exactly saying that the old enigmatic ruin might be a folly, but what he does seem to be suggesting is that our prehistoric ancestors had artistic instincts which were strong enough to influence the design of an Iron Age hill fort.  If a hill fort, why not a stone circle or a stone row, or even a cromlech?  

It's not very much of a leap from there to the suggestion that Stonehenge might itself be an art installation, designed to express something emotional, arising simply from the creative impulse......

We have of course already heard about the theory that Stonehenge was a "sounding box" or a place for giving musical performances -- if banging on big rocks with smaller bits of rock can be counted as music......

And how much distance is there creatively, between a work of art and a folly?

Southern Cardigan Bay coast -- Devensian stratigraphy

Exposure at the northern end of Whitesands Bay, with a lodgement Irish Sea till overlain by deposits suggestive of an ice wastage environment -- similar to the situation at Abermawr.


One of the more confusing sequences in Pembrokeshire -- from the Trwynhwrddyn Peninsula at the northern end of Whitesands Bay.  The two till layers were probably laid down in a single glacial episode very close to a wasting ice edge.

Parrog, Newport -- showing the classic sequence through the Devensian glacial cycle.

Gwbert, at the mouth of the Teifi estuary.  This was a classic exposure of Irish Sea till and interbedded sands and gravels -- but the exposure was completely destroyed during coastal defence works.


Llanina, near New Quay.  There is some debate in this area about tills derived from the Irish Sea Glaciet and from the Welsh Ice Cap.  This is one of the enigmatic coastal sections -- still not adequately studied.








Thursday, 8 November 2018

Cemented raised beaches in Pembrokeshire

The raised beach resting on its rock platform at Poppit in the Teifi estuary.  here the beach is stained with iron oxide and manganese oxide, and is partly cemented.


Another exposure of the raised beach at Poppit, showing a basal boulder bed and an overlying beach made of smaller cobbles.  Does this sequence represent a transgression? All the deposits are stained and partly cemented.

This Poppit section of the raised beach shows distinct layering of pebble beds and beds of sand and shingle.  Drapes of colluvium and sandrock above.  There are strong similarities here with some of the raised beach exposures on the Isles of Scilly.

Poppit — parts of the raised beach are cemented with iron and manganese oxides — up to 1.7m thick. Much lateral variation — traceable along the coast for almost 1 km. Towards E extremity, the raised beach is associated with up to 2m of stratified sands and silts, although elsewhere it is overlain by blocky lower head. Above that, Irish Sea till and thinner upper head.

Here are some notes on other important localities:


North Pembrokeshire

A small exposure of cemented raised beach is plastered against wall of a cove to E of Ogof Golchfa — 75 cm of beach pebbles, overlain by 50 cm of shingle and then 45 cm of sand. All stained and cemented with iron oxide and manganese oxide.

The raised beach exposed at the main Ogof Golchfa exposure is NOT cemented. Leach described cemented raised beach deposits here, but they are no longer visible.

See: The Pleistocene Drift Succession at Porth-Clais, Pembrokeshire. Brian John. https://www.researchgate.net/publication/231973096_The_Pleistocene_Drift_Succession_at_Porth-Clais_Pembrokeshire

At Whitesands Bay (SM733 273), south of the stream, large igneous boulders are embedded in cemented raised beach shingle and are seen resting on a low RB platform. Above that there is main head (uncemented) and then a cemented sandrock.

Cemented and stained raised beach shingle also exposed sometimes at the base of the section in Druidston Haven.

Caerbwdy — fluvioglacial deposits are seen beneath c 3m of stony local till. No raised beach seen, but could well be present.

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

South Pembrokeshire

Broad Haven South — calcite cemented shelly raised beach is seen on the platform, overlain by cemented lower head. Sandrock in places over that, and then more cemented head. The sandrock may be a localised patch or lense. Then we see non-cemented fresh head on top of that, and finally up to 2 m of unconsolidated blown sands and sandloess and then soil.

West Angle — a stained raised beach (50 cm) is seldom seen, but is overlain by a sandy deposit with raised beach pebbles and mixed with head. Above that, the enigmatic silt and clay series…….

On the significance of cementation

The locations of cemented till exposures in Foxhole Cove, Gower.  Are they Later Devensian in age, or much older?  (Photo:  Prof Danny McCarroll /  QRA)

Occasionally on this blog I have mulled over the significance of cemented or concreted deposits -- which might also be referred to as duricrusts, hardpans, duripans or "indurated layers".  In Pleistocene deposits they involve the solution and mobilisation of minerals in groundwater and then their later precipitation because of oxidation, supersaturation or some change in chemical or physical circumstances -- including evaporation, temperature change or infiltration.  In the UK there are two main types of cement: (a) calcite, association with the mobilisation of calcium carbonate in limestone, chalk and related rocks; and (b) iron oxide and manganese oxide cement, sometimes associated with waterlogging and soil formation processes.  In the former case, the cement is normally coloured grey or white, and in the latter the colours range from orange to foxy red through to black.

Here are four of my earlier posts:

On the cemented water-lain deposits near Ceibwr and Witches Cauldron:
https://brian-mountainman.blogspot.com/2015/10/ceibwr-connected-pot-holes.html

On the cemented till and brecciated slope deposits at Black Mixen, Lydstep:
https://brian-mountainman.blogspot.com/2018/05/lydstep-ancient-till-site-confirmed.html

On the cemented raised beach and sandrock at Broad Haven South:
https://brian-mountainman.blogspot.com/2018/04/the-raised-beach-at-broad-haven-south.html

On the cemented till at Watch-house Bay and Foxhole Cove, Gower:
https://brian-mountainman.blogspot.com/2018/11/the-glaciations-of-gower.html

My interest in this issue was triggered by the fact that the editors and contributors to the QRA Gower Field Guide in 2015 attach no significance to the fact that some of the tills described in coastal sections around the Gower coast are cemented, and others are not.  We all know that hard-pan formation can occur in quite recent deposits in what appears to be more or less random circumstances;  I have described small-scale iron and manganese oxide concretions and staining in many sediment sequences, including the Pleistocene sediment sequences at Rhosyfelin, Abermawr,  Fopston, West Angle, Llangolman and elsewhere.   Sometimes these hardened and stained layers appear to be related to old water-table positions.  But the solid cementation of varied deposits several metres thick is another matter entirely, and almost always when such cemented deposits are described in the literature there is an assumption that the cemented deposits are OLD whereas the overlying uncemented deposits are YOUNG.  That is, of course, perfectly sensible........

In many locations across SW Britain the raised beach assumed to date from the Last Interglacial is solidly cemented:

Cemented raised beach at Carn Morval, Isles of Scilly

Cemented raised beach (Gower)

Cemented raised beach (Torquay)

Cemented raised beach, Broad Haven South (Pembs)

Associated with the assumed Ipswichian raised beaches (which are admittedly not always calcite-cemented!)  there are cemented head or slope breccia deposits, sandrock and some deposits that seem to be of fluvial origin. The specialist in this area is Ian West of Southampton University:

West, I.M. 1970. Carbonate Cementation of Some Raised Beaches and Blown Sands of Great Britain. Unpublished M.Sc. Thesis, Liverpool University, 257pp.

The sandrock deposits assumed to be linked in age and environmental contexts with the raised beaches have been heavily studied. One of the more interesting recent studies is this one:

Facies analysis and diagenesis of late Pleistocene shoreline sands, Saunton, North Devon
Sophie Young
The Plymouth Student Scientist, 2012, 5, (2), 486-543

http://bcur.org/journals/index.php/TPSS/article/viewFile/356/335

Stratified sandrock (now thought to be Ipswichian beach sands, for the most part) above the famous pink erratic at Saunton sands, Devon.

A photo from 1962 of the sandrock sequence at Bloody Basin, Saunton.  A classic unconformity!

There are abundant exposures of cemented limestone breccia (lower head) in Pembrokeshire, for example on Caldey Island and at Broad Haven South and Lydstep.  At the latter location, as described on this blog, the concreted limestone breccia (which has come from rockfalls and scree accumulations) is several metres thick, and covers an extensive area at Black Mixen, even roofing over a cave.  This material cannot be stratigraphically linked with either the raised beach platform or the cemented raised beach.  But it does overlie a cemented till:

Limestone bedrock, cemented till and overlying cemented limestone breccia at Black Mixen, Lydstep

One of the first things we learn in geology is that TIME is probably the most important factor in determining which sediments are consolidated and transformed into solid rock, and which ones are not. So it has to be true that the cementation processes referred to in my first paragraph need time, and that the most solidly cemented deposits are most likely (unless we can find other explanations) to be the oldest.

We know that the Lydstep cemented till is pre-Devensian, because it is capped by thick cemented brecciated deposits, and because very close by we can see a Devensian till in a Carboniferous Limestone context which is completely fresh and uncemented.  In this case there is no other explanation that withstands scrutiny.   But what about the cemented tills on Gower?  And what about the cemented deposits at Ceibwr and Witches Cauldron?  The jury is still out........ and we need cosmogenic dating.

I have done a lot of digging around to see what there is in the literature about RATES OF CEMENTATION -- but there seems to be remarkably little research on this topic, from anywhere in the world.   Maybe I have missed crucial articles -- in which case I will appreciate comments from others who are in the know!

It also occurs to me that cave science may have some valuable pointers to what happens out in the fresh air.  There are many places in caves in the limestone districts of the UK where roof falls and collapses have dumped brecciated limestone fragments in large caves and where cementation has then occurred as time has passed.  Are there any good examples which have dates attached?

Weren't the lads who were rescued from that cave in Thailand sitting on a pile of rubble from an old roof collapse?

All advice gratefully  received........

Cave collapse breccia -- apparently uncemented and therefore young?

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POSTSCRIPT

It happens all the time -- one does a post and then discovers -- too late -- all sorts of interesting material in the literature.  In this case, two articles about the conditions in which calcite cement becomes abundant in the environment, leading to the cementation of previously unconsolidated sediments.  Both of the articles cited below make the point that sea-water conditions are important on west-facing coasts, leading to variable concentrations of minerals and in turn influencing the frequency of calcium carbonate trapped in marine organisms including sea shells. There is some relationship with the sea floor geology.  But to put it crudely, the higher the concentration of shelly material in beach sand and offshore sediments, the greater the likelihood of the cementation of sediments in the neighbourhood.  That all makes good sense.  But it does not mean that the importance of the "time factor" is reduced.  After all, on a coastline such as that of Pembrokeshire or Cornwall, conditions now will be broadly similar to the conditions that obtained during previous interglacials -- and the only significant variable (apart, maybe, from temperature and salinity oscillations) will be the position of the shoreline as glacial / interglacial shifts have occurred.   It is still the case, after perusing these articles, that the most solidly cemented sediments an any given locality will be the oldest.

https://www.researchgate.net/publication/261361303

Howie, F.M.P. and Ealey, P.J. 2010. An appraisal of Quaternary calcium carbonate deposits in Cornwall. Geoscience in South-West England, 12, 233-239.
Proceedings of the Ussher Society

ABSTRACT

Cornwall’s calcium carbonate-rich deposits consist predominantly of coastal Holocene beaches, beachrock, dunes, eolianites, tufa and speleothems, offshore coastal maërl beds and late Pleistocene littoral deposits. The majority of these calcareous deposits in Cornwall, with the exception of some tufas and speleothems, were clearly not derived from within Cornwall itself but are largely the product of a regional offshore north-east Atlantic CaCO3 budget controlled by cyclical marine transgressions and regressions coupled with local climate factors operating during the Quaternary.

DISCUSSION AND CONCLUSIONS

The Late Pleistocene to Holocene sands and gravels (Evans, 1990), covering the Devonian/Carboniferous bedrock in the 30 km coastal shelf around the Cornish coast are well-mixed with carbonate skeletal material with “a high preservation potential under present conditions, despite the evidence of bioerosion, disturbance by storm waves and transport of material by currents” (Stride et al., 1999) and are undoubtedly subject to entrainment in the strong tidal pulses prevalent around the south-west UK peninsula. Farrow and Fyfe (1988) considered that much of the north-west European shelf “represents a modern-day equivalent of the ‘calcareous shale’ facies common in the geological record” with the mud fraction of Holocene sediments on the shelf containing in the region of 10–20% CaCO3 rising to over 50% CaCO3 on supratidal mud-flats. The availability of calcium and carbon would therefore tend to sustain the production of shelly biota, the remnants of which are undoubtedly subsequently deposited and recycled on a large number of beaches around the Cornish coast as high- calcium carbonate skeletal shell sands. These sediments lie adjacent to a number of beaches, many of which are composed extensively of calcareous shell sand. These are, in turn, closely associated with carbonate dune fields, beachrock, tufa and, in coastal caves, speleothems. The available evidence indicates that these sediments and deposits have developed where there appears to be no association with limestone bedrock or calcareous head and therefore may be causally interrelated.

The possible effect of a north-east Atlantic influenced carbonate cycle in operation during the Pleistocene (Marine Isotope Stage 7 and/or 5e) is suggested by the occurrence of Quaternary calcum carbonate deposits around exposed headlands along the north and west Cornwall coast and north Devon coast (West, 1973; Gilbert, 1996) where mainland limestones do not occur. In contrast, the Quaternary calcareous raised beaches, cemented sands and tufas along the south Devon and south-west coasts of Wales are associated with limestone bedrocks and carbonate-rich head deposits which may have influenced their diagenesis (West 1970, 1973).

Fossil calcareous maërl accumulations are known from sediments of Miocene to Recent age on continental shelves and are used as stratigraphic markers and indicators of palaeoenvironmental conditions (Foster, 2001). The calcareous endoskeleton of the living algae forms annual growth bands similar to tree rings which make maërl a potential palaeoclimate proxy utilising, for example, Mg/Ca ratios in the individual growth bands. Maërl deposits from north France, Norway, Scotland and Ireland have produced useful on, for example Holocene climatic changes (Freiwald et al; 1991). The palaeoclimatological potential of maërl from Cornwall has not been studied in any detail.

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Carbonate cementation of some Pleistocene temperate marine sediments

IAN M. WEST
First published: May 1973

Sedimentology, Volume 20, Issue2
Pages 229-249

https://doi.org/10.1111/j.1365-3091.1973.tb02047

ABSTRACT

Carbonate cementation of some carbonate and quartz sands in three raised beaches of temperate origins was investigated. The carbonate of the cements was found to have been derived from the dissolution of skeletal debris. The sandstones, so produced, now possess only low‐magnesium calcite, but the original sediments, like adjacent modern beach and blown sands, probably contained low‐magnesium calcite, aragonite and some high‐magnesium calcite, all of skeletal origin. In meteoric water the dissolution has occurred of all carbonate within minute, tubulelike, volumes of sand. Concurrent deposition in adjacent volumes of sand of low‐magnesium calcite formed cements that are irregularly nodular or uneven on a small scale. Aragonite within the minute nodules has been replaced paramorphically by low‐magnesium calcite. Additional local carbonate cements were formed at later dates, around and within solution pipes.




Tuesday, 6 November 2018

HHT's grand day out -- and the Stonehenge greystones



I came across this in the file of ancient reprints.  It's a translation of an article written by OT Jones in 1966 -- and it describes how the  bluestones - Stonehenge connection was initially made by the geologists.

It all started on a grand day out in the summer (one presumes) of 1908,  when Thomas, Cantrill, Strahan and Jones made a jolly train expedition to Rosebush railway station, walking from there to Crymych along the Mynydd Presely ridge before taking an evening train home from Crymych railway station on the "Cardi Bach."   They obviously looked at a lot of rocks on the way.   DC Evans was obviously their guide, and I have read elsewhere of his role in supplying material later on for HHT to look at.

Between that first trip and the serious work on the bluestones in 1918, ten years elapsed, and the First World War disrupted everything.  Maybe it was the end of the war that provided the impetus.

Note that Jones, in his Welsh-language article, calls the stones "Cerrig Llwydion"  -- not bluestones but GREY STONES.