Sunday 5 November 2017

Phyllite rock layers at Kintra



The geology of Islay is very complicated. I was very taken by the twisted layers in these rocks at Kintra. Look also at the general angle of the layers in the wider picture. In the top picture, the layers seem to go through a 90 degree angle. I was hoping for an unconformity but they are all the same type of rock, just hideously twisted. The rock is called phyllite. It is a form of metamorphosed slate. I read that in slate, clay molecules line up in a preferred orientation. In phyllite it is small crystals of mica. That sounds like schist, but apparently the trick in schist is that it is larger flakes of schist that line up. My source says that the foliation (layering - from the word for leaves) is "crinkled or wavy in appearance" which indeed it is. https://en.wikipedia.org/wiki/Phyllite    http://earthwise.bgs.ac.uk/index.php/Appin_Group,_Grampian_Caledonides