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This is a blow-up of part of Phil's picture, taken last winter after the first season's excavations near the lower part of the rock face and before the much larger 2012 excavations (which removed more of the vegetation and soil from higher up in the gully).
One thing that shows up here is the rough fan-shape of the sediments coming down onto the main valley floor from the gully. There has been a lot of sediment movement here -- and this is of course confirmed when we look at the thickness of the material which has accumulated over the litter of scree and broken blocks.
18 comments:
Brian, a question
How did the 'fan-shape' sediments along the excavated face of Rhosyfelin form? These seem like mud slides from above the Crag where there is also very dense vegetation growth.
Kostas
Fans are created where a flowing medium carrying sediment encounters a change of gradient which in turn forces a loss of carrying velocity, which in turn causes debris to be dumped -- big fragments (boulders and stones)first, then gravel, then sand, and finally silt and clay. The finest materials may be carried well clear of the fan since they can remain in suspension even if flow velocities are quite low. No need for mud slides.
That isn't to say there are no mudslides here, maybe mixed in the periglacial slope deposits. I hope that when the MPP team publishes its field data, we will get a proper stratigraphy, examined by somebody with a knowledge of sedimentology and geomorphology.
Looking at the picture, Brian, these fan-heaps of soil against the rock face look more like mudslides. At any rate, could such heaps of soil survive snow melts and rainfall coming down the rocks and the gully for 10,000 years – if these formations are glacier or periglacier?
Any bets on the existence of buried rocks and spree on the other un-excavated side? And if it can be shown both sides have similar buried clutter of stones, what does that do to MPP's “quarry” theory? Certainly, no human quarrying of stones could have existed on the “head side”, as we have been shown in a previous post!
Kostas
SCREE, Kostas...... not spree. What do you mean, the "look like mudslides"?? I am at a loss as to what you mean. I would be pretty certain that there would be accumulations of broken blocks and scree on both sides of the crag.
Sorry Brian! Blame it on my sticky Greek keyboard! As for 'mudslides', another abuse of language perhaps? What I should probably have said was dirt drip from above.
Check the photo for similar smaller heaps of dirt building up against the rock surface nearer to the tip of the rock face. Look at the top of the crag to see some paths on the soil surface of such dirt/mud/water tracks contributing to the dirt heaps below. I wont be surprised if more such smaller fan-heaps existed before the first MPP excavation – all the way to the very tip end of the rock face.
Could these fan-heaps of sediments be glacial or periglacial? In my opinion, no! Why? My sense is such heaps of dirt cannot be 10,000 years old. Or they would have settled flat by now. By show melt and rainfall if for no other reason. That's what I think. Am I wrong?
Kostas
From what I am told they have not excavated to glacial periods beyond a few holes of special interest. So what we think we see is of a more recent vintage and likely the result of muds eroding down the slope towards the river - although I think geologists have a posher description, dirt dripping is ok too - maybe even a few mini-slides, but his might be over dramatic
Brian,
I believe the question of MPP's “quarry” can be answered! Please comment on the following method.
1)RC date the formation of the 'rock face heaps' of deposits by using samples from deep in the heap – close to the bottom and to the rock face. The assumption here is these deposits formed from dirt slides down the crag. Many such samples would need to be taken to discount the possibility that per chance much older material stuck in the crag were also deposited in the 'rock face heaps'. The most recent RC date should be considered as most meaningful.
2)The date of the formation of the 'rock face heaps' also dates approximately when the nearby river retreated from the crag. Since, if river torrents surrounded the crag, such dirt heaps could not have formed. As the torrents that polished the rock face would wash them away. Such 'rock face heaps' would start forming as soon as the river retreated from the crag. This RC date would thus mark the earliest time when human quarrying would have been possible.
Now if Myris could channel to tell us if any RC samples were taken from the excavated 'rock face heaps' and what the dates were, we're done! And if I am wrong and these RC dates are earlier than say 3000 BC, I wont speak of this again in your blog.
Kostas
My predictions for 2013.
MPP will publish definite proof that at least one megalith quarried at Rhos-y-felin ended up at Stonehenge.
A Prescelli volcanic erratic will be discovered some 15 miles NW of Stonehenge and the provenance confirmed by the learned doctors.
The debate continues.
In September there will be more digging and more debate.
Kostas will develop his theory about underwater neolithic sub-mariners leaving flint tools at Rhos-y-felin.
The Health Farm professors will come up with some much needed evidence for healing wells in E. Prescelli.
Myris will continue to be gnomic in the Anglo-saxon sense - mysterious and prophetic.
Brian will hopefully keep this blog going and inject lots of common sense and scientific rationality.
Neolithic roads will be discovered
Orkney will become even more significant.
Lake Brynberian too.
I look forward to the New Year and wish everybody good health and lots of stimulating ideas.
Chris,
You can ridicule but you cannot refute!
We could determine when the dirt heaps formed by taking RC samples deep within them. But the telling question is why these did not form any earlier? Certainly the same conditions that formed these dirt heaps would have also formed them earlier – if the Crag was so exposed.
I argue the reason why these dirt heaps did not form earlier is because the Crag was in the middle of a raging and wide river. All the evidence in the photos I've seen seem to indicate this. But if there is evidence not shown which contradicts my hypothesis I am open to reconsider.
My prediction for 2013? All evidence found by MPP that does not fit his theories of human agency will not see the light of reason!
Kostas
Kostas -- let's assume, shall we, that in due course the stratigraphy will be properly described, and the radiocarbon dates that are obtained will be reported accurately and objectively, and then used in the process of some logical process to determine the full history of the site. Until then, speculation about floods and dirt is a waste of time...
Brian,
I am scouting the territory before the debate begins. If it ever begins with ALL the evidence on the table! Can you be sure all will be available? And how would we know if it is or not?
The tight control we've seen exercised over 'proprietary data' and its filtered release to the public worries me. Now we even have university positions created for “Public Engagement in Science”.
Kostas
Mr Johnson
Who told you about the key Preseli erratic NNW of SH? Will it become as famous as Rosetta?
Ah Thomas the Rhymer in AS mode-(quite nasty potters rather like IA pots)All those wonderful and so very, very Wode(n)-like, horny riddles full of up-right thorns.
M
Myris,
something dreamed up in my crystal cave, like many prophecies.
Ah Mr Johnson
Take care or you will share the opprobium (or even obreption)of a Person from Porlock.
Alph.
Is Kostas connected to Coleridge's Kubla Khan too?
Tony,
Let me help you. Kostas is connected to sensible reason and truth!
I know … unbelievable in today's world!
My dear Myris,
Would that be the rhyolite,
That hides close the Sky at Night,
One letter away from a corpse?
There are others around,
They rest on the ground,
Where water on wood creates warps.
Now was this erratic,
A frozen aquatic,
Dumped a long time ago?
Or chilled to the bones,
Did man drag the stones,
With journeys on land, to and fro?
For a few more examples,
And interesting samples,
There’s really no need to shiver.
For they live in array,
Where the Sun ends the day;
Look just to the west, by a river.
BRAVO, BRAVO, BRAVO my dear GS.
Far better than that odd Stevie Smith poem on the Porlock intrusion. (precis... she is depressed)
(I used to go past her scruffy terraced house in Palmers Green on the way to Saturday Morning Pictures in the 1950s -to see the real be-blonded Flash Gordon) I do not remember her being a local celeb or ever mentioned in the local rag. How life and ART have changed.
Fab. poem GS now a nonsense poem about Alice perhaps.
M
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