. The Quarterly journal of the Geological Society of London. in vol. lv (1899) pp. 661-65. As the lime-stones and quartzites of Bardsey are precisely like those of Northern Anglesey,no lithological description is given of them in the present paper. 524 DE. C. A. MATXEY OX THE [Oct. I913, of inclusions of grit, quartzite, and limestone, sometimes rudelyphaeoidal, sometimes irregular, and often more or less rounded,and of all sizes from large boulders to tiny pebbles (fig. 6,below). Yet, even in tbese shattered strata, traces of overfoldingcan be seen, as fragments of the same limestone
. The Quarterly journal of the Geological Society of London. in vol. lv (1899) pp. 661-65. As the lime-stones and quartzites of Bardsey are precisely like those of Northern Anglesey,no lithological description is given of them in the present paper. 524 DE. C. A. MATXEY OX THE [Oct. I913, of inclusions of grit, quartzite, and limestone, sometimes rudelyphaeoidal, sometimes irregular, and often more or less rounded,and of all sizes from large boulders to tiny pebbles (fig. 6,below). Yet, even in tbese shattered strata, traces of overfoldingcan be seen, as fragments of the same limestone-band recur againand again at various heights and at various places in the of thestrata is admittedly due to the crumpling effectof compression acting differentially on hard, brittle, and lessyielding beds (the grits and limestones) when interbedded withsofter and more extensible slates, with the result that the formerhave broken up and the latter have flowed round the fragments. Fig. 6.— Crush-con glomerate in the cliff at Pen C. A. M. photo. In this locality the disruption seems to have acted along the septaof small overfolds or buckles in steeply dipping Fig. 1 of PL XLIX represents a portion of a cliff—not onBardsey itself, but on the adjacent mainland near St. Marys Well,south-west of Aberdaron. It has been introduced to show thepassing of interbedded bands into a crush-conglomerate, and alsothe deformation of a massive bed of quartzite into two wedges. i See G-. Barrow, On Buckled Folding Geol. Mag. dec. 5, vol. ix (1912)p. 518. Vol. 69.] GEOLOGY OebaRD3EY ISLAND. 525 IV. Post-Movement Intrusions. Three olivine-dolerite dykes with a north-westerly to south-easterly trend have been noted in the course of the are quite uncrushed, and occupy fissures which cut acrossthe structures of the surrounding strata. One of them, some40 feet or more wide, has been excavated by the sea to form thelittle harbour at Catn Enlli. Another
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