Geological Society of Glasgow


Lochaber Geopark





Gallery Page 1

SE of Craignure, Mull  NM73409,35946.  Possibly an intrusion of Craignureite into Jurassic sediments, but looks rather like a lava flow over a channelled palaeo surface, Tertiary

S end of Gigha NR 63060,46387.  Metabasite, Dalradian, being altered tuff complete with numerous volcanic bomb clasts.

Port Selma boulder bed, Benderloch, NM 90230,38026.  Chaotic mixture of local clasts in Dalradian sediments.  Probably a mass transport slurry

BELOW:  Photomicrographs of thin sections of loose rocks from below Dunollie Castle.  The rocks are marked on the geological map as conglomerate, Lower Old Red Sandstone, Devonian.  In hand specimen they look massive and an even brownish colour.  However, they are clearly conglomerates as can be seen from the photomicrographs of thin sections.  The rocks comprise rounded clasts of different feldspar-containing igneous rocks set in a matrix of volcanoclastic sand grains.  The rock has been pervasively altered to an even brown colour, and the only minerals remaining unaltered are the feldspars.  In one of the photomicrographs a cavity has been filled with a growth of small crystals of quartz, arranged in layers.  The photographs were taken in plane polarized light.  The width of the field of view is 3.5mm.


Photomicrographs by Julian Overnell

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