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| Keywords: The Quarterly journal of the Geological Society of London (14052682086).jpg 198 <br> H HICKS OjS CAZilBEIA COXGLOMEEATES Ilf <br> a <br> o <br> <br> ¢I <br> I <br> basal conglomerate from its position under the lowest purple slates <br> as worked in the Alexandra quarry in the district The con- <br> glomerate is marked as altered Cambrian in the Survey maps I <br> examined the conglomerate also on the west side of the ridge about <br> Glyn-Llifon and there also recognized clearly that the conglomerates <br> were mainly the result of the denudation of the Pebidiau and quartz- <br> felsite rocks of the area with occasional fragments of Dimetian <br> That there may be no possibility <br> 5 oi doubt as to the meaning of the <br> interpretation given by the Sur- <br> veyors in their latest remarks on <br> the so-called intrusive masses <br> marked on their maps which we <br> claim to be of Pre-Cambrian age <br> in Caernarvonshire I quote the <br> following explicit passage from the <br> last edition of the Survey Memoir <br> vol iii p 200 1881 ” ' On Twt <br> Hill the rock consists of a mixture <br> of felspar and quartz forming a <br> distinct binary compound such as <br> was once called granitella and is <br> now often called aplite or granu- <br> lite But for the absence of mica <br> it would be a true granite <br> jSTear Brithdir a mile and a <br> half south of Menai Bridge the <br> continuation of the crystalline <br> mass is a purple quartz-porphyry <br> and nearer the bridge a quartz- <br> porphyry much resembling that of <br> Llyn Padarn in the pass of Llan- <br> beris Between these points and <br> Caernarvon though much of it is <br> a quartz-porphyry it is not always <br> easy to give it a definite name ; for <br> though still composed of felspar <br> and quartz it sometimes passes <br> into a rudely foliated rock rising <br> here and there in bosses through <br> the glacial debris that fills the <br> hollow And yet though it never <br> perhaps deserves the name of <br> gneiss to me it sometimes con- <br> veys the impression of stratified <br> rocks in a very advanced stage <br> of metamorphism which for the most part may have originally <br> consisted of the Cambrian strata that lie between Bangor and Dol- <br> deilo and perhaps of some of the SUurian strata that border it from <br> Dol-deilo to Caernarvon This may possibly be explained on the <br> 6 <br> O DC <br> O « <br> PPOP <br> S <br> cS c3 <br> e r iS 36940981 113697 51125 Page 198 Text 40 http //www biodiversitylibrary org/page/36940981 1884 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 40 1884 Geology Periodicals Smithsonian Libraries bhl page 36940981 dc identifier http //biodiversitylibrary org/page/36940981 smithsonian libraries Information field Flickr posted date ISOdate 2014-04-30 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/14052682086 2015-08-26 05 55 18 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1884 Photos uploaded from Flickr by Fæ using a script | ||||
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