. The Quarterly journal of the Geological Society of London. which have been described as•such are bedded rocks which have been torn to pieces by earth-movement, and are now in the condition of crush-breccias andcrush-conglomerates. Similarly, the isolated quartz-knobs ofJ. F. Blake, of which several good examples occur in Bardsey,prove to be, as in Northern Anglesey and elsewhere, portions ofmassive beds of quartzite that have been broken up into lenticlesand separated from their fellows by differential movements betweenthese hard masses and their less rigid associates. The rocks are excellen
. The Quarterly journal of the Geological Society of London. which have been described as•such are bedded rocks which have been torn to pieces by earth-movement, and are now in the condition of crush-breccias andcrush-conglomerates. Similarly, the isolated quartz-knobs ofJ. F. Blake, of which several good examples occur in Bardsey,prove to be, as in Northern Anglesey and elsewhere, portions ofmassive beds of quartzite that have been broken up into lenticlesand separated from their fellows by differential movements betweenthese hard masses and their less rigid associates. The rocks are excellently exposed on the shore and in the sea-cliffs, but inland, except on Mynydd Enlli, they are largely coveredby boulder-clay. The accompanying coast-sections (figs. 1, 2, & 3,pp. 517, 520) are given, in order to illustrate the geological structure; 1 See Sir Archibald Geikie, Geol. Mag. ser. 4, vol. iii (1896) p. 481; and?C. A. Matley & W. W. Watts, Q. J. G. S. vol. lv (1899) pp. 657-66 & 677-78. Vol. 69.] GEOLOGY OF-BARDSET ISLAND. 517 m k\. and they, as well as the map (PI. L),should be referred to when the following-description is read. It is not claimed,however, that the folding indicated inthese sections is more than semi-dia-grammatic, it being impossible to de-termine in many cases -whether theisoclinal folds (which are themselvesmuch broken) are anticlines or syucliues. (a) The Northern Coast.(Fig. 1.) In the north-western corner of theisland, in the cliffs between Ogof Lasand Ban y Bhigol, the granite discoveredby Miss Raisin is exposed at five locali-ties, but these exposures may representno more than a single sill repeated byfolding. Thus, when the two granite-bands and the associated sediments onthe northern shore are examined, thesuccession of the beds (fig. 1) is seento be such as it would be if they weredisposed in an isoclinal fold, whetheranticline or syncline. Between thegranite-bands occur thinly and evenly-splitting, well-cleaved, green, sandyslates, which
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectgeology, bookyear1845
