Mynydd Preseli ice margin

I have been looking through this excellent report on the Teifi catchment, published in 1997.  I'll come back to it with more of the useful material culled from the literature by the authors.  But for the moment, this map caught my eye, since it is right in line with my current thinking on where the ice edge might have been in North Pembrokeshire at the time of the Devensian glacial maximum, around 20,000 - 18,000 years ago.

In line with much of the recent work done by BGS surveyors, they show Welsh ice affecting the upper catchment of the Teifi, as far downstream as Llandysul.  On its western edge, between Llandysul and the Ceredigion coast (which was not there at the time) there was a contact zone with Welsh ice to the east and Irish Sea ice to the west.  Carningli and Dinas Mountain are shown as completely inundated by the Irish Sea ice stream -- and more and more of the field evidence published on this blog now appears to support the idea that the ice edge lay along the northern flank of the Mynydd Preseli ridge, with the Brynberian Valley (including the Rhosyfelin area), Carnedd Meibion Owen and even Cwm Gwaun overridden.  This means that the morainic accumulations at Pont Ceunant, Cilgwyn and Tafarn y Bwlch may owe their origins to temporary stillstands or slight readvances during  a prolonged deglaciation phase.  The thick accumulations of sands and gravels in the Monington - Moylgrove area must also date from this episode of ice melting.

More fieldwork is required.  Watch this space........

Source:
R A Waters, J R Davies, D Wilson and J K Prigmore.  1997. A geological background for planning and development in the Afon Teifi catchment.    British Geological Survey Technical Report, WA197I35.102pp.