THE BOOK
Some of the ideas discussed in this blog are published in my book called "The Bluestone Enigma" -- available by post and through good bookshops everywhere. Bad bookshops might not have it....
To order, click
HERE

Saturday, 11 February 2012

Pembrokeshire's last glacier

My thanks to Jonathan Lee and Aberystwyth University for more amazing images of the Preseli area -- created using a technique called digital stereo aerial photography  -- representing attitudinal changes to an accuracy of 2m and then creating a sort of 3D effect through the application of "false lighting and false colour."  Notice that the light falls from reasonably high in the NE -- which it almost never does in the UK in reality.  That's a technique used on traditional relief maps for many years -- it so happens that the eye and the brain manage to interpret the shape of the land more accurately than if the light falls from other quadrants (which causes an inversion of relief, causing peaks to show up as pits and vice versa.)
More info here:
http://www2.getmapping.com/Products/Getmapping-Height-Data

At any rate, this is a fragment of a larger image which shows the site of Pembrokeshire's last Ice Age glacier, in Cwm Cerwyn, immediately to the east of Foelcwmcerwyn or Preseli Top.  The headwall of the "incipient cirque" is aligned towards the ESE -- which is unusual, since broadly south facing hollows are supposed not to be good places of cirque development in the Northern Hemisphere.  Most cirques have a preferred orientation of NE.......

But here, in the Younger Dryas, around 10,500 years ago, there was obviously sufficient precipitation coming in from the west to collect in the lee of Foelcwmcerwyn to create a small cirque glacier that survived for a few centuries.  If you look carefully you can see a little hummock of moraine on the floor of the depression -- and if you examine that on the ground, you can find striated stones and boulders.......

Incidentally, this glacially steepened slope is just about the only place on Preseli where you can actually fall off, if you are not careful!

10 comments:

Anonymous said...

Brian

Vincent Gaffney (CBA research report 160, 2009) suggests the Younger Dryas was 12,625BC to 10,950BC by the 10,500BC you stated we was in the Hottest period of the Holocene.

Moreover, The Late Glacial between 12,600 and 11,750BC there is a strong climatic gradient across Europe with the area known as Britain considerably warmer to the east at the same altitude; this accords with the 'older Dryas', a climatic period which essentially is 'missing' in Britain.

Are you claiming Wales is not part of Britain?

A.N.Other

BRIAN JOHN said...

I don't care what Vince Gaffney suggests -- there are hundreds of other papers too. The consensus is that the Younger Dryas finished around 10,000 years BP. Are you getting your BC mixed up with your BP? There are traces of the Older Dryas in Britain -- but much discussion about how well developed that "cold snap" was. The overall pattern during the Late Glacial was one of gradual climatic amelioration, with some slight disturbances. The fact that there was glacier expansion in the Younger Dryas is not in doubt.

Anonymous said...

Brian

I'm sure Gaffney has is dates right - but have you?

Of course if he is right (and his publications have outsold yours by a long long way) your glaciation theory is toast.

A.N.Other

BRIAN JOHN said...

More nonsense, Anon. How is it that you are sure Gaffney has got his dates right? Are book sales an indicator of scientific reliability? I dare say that Velikovsky and Von Daniken have sold more books than you have -- does that make them any more reliable? Get real.

By the way, I did not refer to 10,500 BC. I referred to 10,500 BP. World of difference. You are clearly a very confused person.

BRIAN JOHN said...

Anon -- for your edification: Fitch and Gaffney 2011: "With the onset of the Younger Dryas (10,800-10,000 BP) Britain
experienced climate deterioration. The GISP-2 ice-core data suggests a rapid fall in mean temperatures of up to 7 degrees C (Barton 1999; Atkinson et al 1987). This cold, wet climate would have led to significant snow falls which fed localised glaciers in Scotland and north Wales (Alley et al 1993). There is limited evidence of human activity for this period, and it is possible that Britain was abandoned for a period around this time (circa 10,500BP)."

Anonymous said...

Brian

Got the dates wrong again! - takes a big man to admit that, and a little man to change the blog!

A.N.Other

BRIAN JOHN said...

Mr Other -- I have no idea what you are talking about -- and I have certainly not changed the blog. When I say "10,500 years ago" I mean "10,500 years BP." Everybody knows that. Terminating this one now, since we are clearly going nowhere...

Anonymous said...

Devensian Lateglacial environmental changes in Britain: a multi-proxy environmental record from Llanilid, South Wales, UK Original Research Article. QSR Pages 475-520

"Mean July temperatures of 10–11°C characterised the Loch Lomond/Younger Dryas Stadial (Greenland Stadial 1) between ca 12,600 and 11,400 cal yr BP, during which time a scrub tundra with Betula, Salix and a range of open-habitat taxa became established locally. The onset of the Holocene Interglacial at ca 11,400 cal yr BP is marked by an abrupt temperature rise of the order of 9°C, and by the rapid expansion of Betula woodland"

Is where Gaffney claims his information - he seems confused - aren't we all.

10,800 - 10,000BP can't be correct because of Star Carr has been carbon dated as a settlement during that period!!

A.N.Other

Sorry forgot, you want to concentrate on fantasies rather than facts!!

BRIAN JOHN said...

I meant to delete that -- but pressed the wrong button! The Younger Dryas has lots of dates -- not always easy to match because of different correction factors applied to C14 dates in particular. And remember that glaciers in the uplands remained in place for several centuries after the temperature started to warm up. Because the Loch Lomond Advance was of limited extent, there is no problem at all with having settlements occupied by Palaeolithic hunters / tribal groups even at the coldest part of the Younger Dryas. End of discussion -- I am fed up.

Geo Cur said...

Vince Gaffney ,although not mentioned in the main text ,was also involved in the nonsense of the Cursus pits "alignments" and "procession "see http://brian-mountainman.blogspot.com/2011/12/cursus-great-pits.html and comments