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Friday, 24 February 2012

North Pembrokeshire Glacial Striations


The other day I forgot to give the hard data on the glacial striae plotted in 1962-1965 in North Pembrokeshire.  During my fieldwork I plotted hundreds of striae, mostly on smoothed rock slabs close to the coastline.  The magnetic variation at the time was 7 deg and 20 minutes west of grid north.  The compass directions below are as I recorded them -- on the map above they are corrected.  Within the circles I have only put selected striae directions -- deemed to be the most common.

Note that ice movement directions can be heavily influenced by the nature of the bedrock and the orientation of the coastline and the cliffs -- so a "regional" ice direction movement may be locally disrupted, with ice moulding itself to the topographic features of the coastline.  There may be highly localised swings of maybe 30 degrees to either side of the regional ice flow direction.  But the overall ice movement directions do come through if you measure enough striations......

 Striated bedrock slabs, Whitesands North


Here are the records:

1.  Ogof Golchfa:  90 -140, mostly 125, 80, 33, 25
2.  Whitesands South:  115 -190, mostly 135
2.  Whitesands North:  100 -160, mostly 133, older striae 180 - 230, mostly 223
3.  Porthmelgan:  120 - 160, 140 - 190, 230, mostly 160
4.  Pen Deudraeth (Aber Mawr)  122, 148 (older?), 173 (newer)
5.  Parrog (Newport)  113 - 173, mostly 160
6.  Newport Sands:  160
7.  Gwbert (Cardigan):  115 - 155, 163, 183, mostly 135

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