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Tuesday 27 March 2012

Periglacial blockfield on Carningli


I have often referred in the past, on this blog, to periglacial blockfields.  Here is a classic example, on the undulating plateau to the west of Carningli summit.  Last year, burning stripped off a cover of gorse and heather, and now the vegetation is re-establishing itself.  But the litter of angular and jagged boulders and stones of all sizes is readily apparent. 

Although there is some till here, and occasional erratic boulders, most of these rocks are very local -- dolerites, rhyolites and some gabbros and ignimbrites.  Frost has done most of the work here, covering this landscape with a layer of frost-shattered debris, maybe over several glacial episodes.  There is no trace of patterned ground (circles or polygons) -- but there are occasional "stone take" hollows, traces of old field boundaries and trackways -- this has been an inhabited landscape since Neolithic times, and there is a substantial hillfort on the summit in the middle distance.  That is assumed to be Iron Age, but parts of it might be older.

7 comments:

chris johnson said...

Very interesting observations. I walked this area several times and there are lots of mysterious bumps and hollows. It is likely too exposed to have been used for cultivation or even habitation in the neolithic but nevertheless the general area has been intensely used in the past. I think there is substantial peat build-up so perhaps the fire did not reveal all.

BRIAN JOHN said...

These ridge tops are essetially dry heathland, not peat bog. so there is virtually no peat here -- if you dig, tou are straight down into rock rubble. There is peat further to the west, in the hollows -- and some old peat cuttings too.

Yes, there are abundant traces of occupation in this area -- especially on the north and south flanks of the ridge. Took some nice pics yesterday -- will post them soon.

chris johnson said...

I am puzzled about an apparent contradiction between Carningli as a major hill-fort and the abundant stones on the slopes, apparently lying casually.

Either someone did not take the defense seriously, or someone else went to inordinate trouble to destroy the fortifications and move the stones well down the slopes.

I suspect Carningli was never fortified seriously which would also be surprising given its strategic location dominating a major harbor.

Did anybody ever excavate the cairns - professionally I mean?

Your remark on peat is fascinating too. Shows how sensitive the area is to relatively minor differences in altitude - although perhaps I do not understand peat formation sufficiently..

BRIAN JOHN said...

Scree slopes, Chris -- especially on the southern slopes where I think there was a wind-scoop. There were more than enough stones just lying about for the building of a substantial fortified settlement. and the fortifications ARE impressive -- and there are hut circles in the Carningli "village" -- look up Carningli on Wikipedia and you'll see my map there.

Peat forms on very gentle gradients and needs waterlogged conditions. The Carninli ridge top is too dry, and probably always has been.

BRIAN JOHN said...

By the way -- yes, the fortifications on Carningli were "slighted" or deliberately destroyed. The archaeologists are pretty convinced of that.

Davey said...

Was watching the (un)controlled burning on Carn Ingli from Dinas Head tonight. It looked like there were a number of long lines of flame from just above Ffordd Bedd Morris and a few other isolated sites.

Could be worth a scratch around in the next few days.

Any news on the return of the Bedd Morris stone. I heard it waas at Castell Henllys and it appears that they migh have excavated the last socket hole as it is now turfed over. They have set back the fence as if they plan to 'plant' it further back away from the road.

BRIAN JOHN said...

I wondered when the burning was going to start -- they have left it very late this year. It's so dry up there now that I should have thought it will be impossible to control burns, if the wind picks up.....

No idea what's happening to the Bedd Morris stone.