756 Geological Society. 



Some post-movement dykes of olivine-dolerite occur, with a 

 north-west to south-east trend. They are probably of Tertiary age. 



Glacial striae and boulders indicate that the island was invaded 

 by a portion of the Irish Sea ice-sheet which, after crossing Anglesey 

 to the west of Red Wharf Bay in a south-westerly direction, was 

 deflected in Carnarvon Bay and traversed Bardsey in a south- 

 easterly direction. This deflexion is tentatively attributed to the 

 pressure of ice radiating from. Ireland. 



There are doubtful indications of a post-Glacial raised beaoh at 

 18 to 20 feet O.D. 



In an Appendix Dr. J, S. Mett describes the petrographical 

 characters of the granites, the pillow-lavas and their tuffs, and the 

 diabases. 



2. ' The Loch Awe Synoline (Argyllshire).' By Edward 

 Battersby Bailey, B.A., F.G.S. 



Mr. J. B. Hill's classification of the sedimentary schists of the 

 district, into the Loch Awe Group above, and the Ardrishaig Group 

 below, is accepted. So also is his reading of the Loch Awe Syncline. 

 This syncline is a comparatively shallow trough, with well-marked 

 fan-structure due to small-scale isoclinal folding, in which the limbs 

 of the folds are vertical along the axial belt of the syncline, and 

 inclined outwards on either side. 



There are, however, two modifications of Mr. Hill's original 

 interpretation, both of them already dealt with, in part, by Dr. B. N„ 

 Peach and the author in the Geological Survey Memoir describing 

 the southernmost portion of the region (Sheet 28), One of the 

 proposed alterations is concerned with the numberless igneous rocks 

 folded along with the sedimentary schists. Many of these are 

 obvious intrusions ; but some, as Dr. Peach showed in 1903, are 

 certainly lavas. In the present paper, Dr. Peach's volcanic zone is 

 traced throughout the whole district, where it maintains a constant 

 horizon in the Loch Awe Group. This brings us to the second 

 suggested modification, affecting, as it does, details of the strati- 

 graphy of the Loch Awe Group, for which the following sequence 

 is proposed $ — 



Loch Avich Green Slates and Grits (volcanic rocks in the lower part). 

 Tayvallich Black Slates and Limestones (volcanic rocks throughout). 

 Crinan Grits and Quartzites. 



Shira Limestone, constituting a passage-zone down into the Ardrishaig 

 Phyllites. 



Attention is drawn to evidence, already published, that the 

 order of superposition of the sediments in the Loch Awe Syncline 

 corresponds with the original order of sedimentary superposition. 

 Finally, a recent suggestion of Mr. Hill's is adopted, in which he 

 correlates the extremely low grade of metamorphism of the rocks 

 of the central part of the Loch Awe Syncline with their high 

 structural position. The "hypothesis is that these rocks were not 

 deeply covered during their metamorphism, and accordingly were 

 never raised to any very high temperature. 



