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Monday, 14 January 2013

North Pembrokeshire glacial map

 Click to enlarge.....

In my attempts to understand the Pleistocene history of the Rhosyfelin site, I came across this old map made many years ago by Prof David Bowen.  It incorporates info from many different sources.  The red dot (added by me) shows the location of the Rhosyfelin dig.  There are lots of glacial features (including many that are quite fresh) to the north of it, so even without knowing whether Lake Brynberian actually existed or not, and without having any shorelines to work with, we can say with some certainty that the dig site lies somewhere quite close to the Devensian ice limit in North Pembrokeshire.  More to follow.......

8 comments:

Dave Maynard said...

Are you aware that both Trefigyn and Pant Gwyn quarries had conditions regarding study of glacial features as part of their recent permissions to continue operation? Do you know who is doing that work?

It would appear to be very pertinent to this discussion.

BRIAN JOHN said...

Dave -- I would imagine this is standard with sand and gravel quarries -- to ensure that they do not try to block off access fro geomorphologists!! Neil Glasser and the other guys at Aberystwyth may well have looked at these quarries already -- and may be looking at them again in the future.

Constantinos Ragazas said...

Brian,

This map seems to show the present river at Rhosyfelin to be a large meltwater channel which further south is a small meltwater channel that originates from the northern side of Preseli some 5 km away at a height of some 900 m and in line with Mynydd. Am I reading the map properly? Is that in agreement with your own knowledge of this?

Can you add a couple of more dots to show where Rhosddu Channel and Pedran Channel are located here?

Kostas

BRIAN JOHN said...

They are both to the east, Kostas, off the map.

BRIAN JOHN said...

Kostas -- beware -- the altitudes are in feet on this map, not metres. the Brynberian rover starts in a series of small streams on the mountainside which come together near Brynberian. From Brynberian down to the gorge near Rhosyfelin, the river is contained in a distinct valley with steep sides.

Constantinos Ragazas said...

Brian,

I was mislead by the mixed units used in the map. Though distances in it are measured in km, altitudes are measured in feet. No expected consistency there, I am afraid! Thanks for clarifying.

Could you in some other descriptive way depict the location of these Channels? Say, so many km from the edge of the inlay on the map?

The view is now emerging. The current river at Rhosyfelin was at one time a wide meltwater channel (according to this map). This is in agreement to what I have been saying. Where we really differ is in the time period when this river engulfed Crag Rhosyfelin.

Certainly RC dating done right can answer this question. But MPP and his loyal entourage are not saying … and cannot be shamed to revealing these dates!

Kostas

BRIAN JOHN said...

Kostas -- don't jump to conclusions here. MPP and his colleagues might have collected a lot of samples for radiocarbon dating. And pollen analysis takes time. They might not have any results yet -- or not enough to get a full picture.

Constantinos Ragazas said...

Brian,

I do appreciate the slow pace of scientific facts to emerge. But how do you explain the “rush to announcement” of fanciful speculations, e.g. “human quarries”? Or no information coming out of MPP's black-hole that in any way opposes his narrative?

Concerning 'pollen analysis', I have some concerns. Such studies assume the pollen count found in the ground was from plants growing in those grounds. But when there is much natural geographic upheaval through glacier advances, meltwater streams, glacier lakes, and even gale winds, how can we be sure the pollen found did not come from elsewhere and possibly far away and from higher elevations?

If studies of pollen analysis, for example, show Salisbury Plain was once a thick forested area, what happened to that soil necessary to support such forestation? Why the soil now hardly supports the growth of shrubs, let alone mature trees?

It gets curiouser and curiouser with every thought out fact …

Kostas