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| Keywords: The Quarterly journal of the Geological Society of London (12735780365).jpg GRITS OF CORWEN NORTH WALES <br> 209 <br> the direction of the second pressure may coincide with that of the <br> first ; and though perhaps the result may be more intense cleavage <br> in the previously cleaved rocks no crossing of cleavage-planes could be <br> produced ; and moreover in cases where the second cleavage is very <br> intense or the rock very susceptible of cleavage this would entirely <br> obliterate all previously existing divisional planes as notably in the <br> volcanic slates of the Lake-district where we find joints and faults <br> quite healed and the rock splitting along the cleavage-planes only <br> The beds below the Grits are as a rule bluish rab i e a shivery <br> mudstone breaking along bedding joints and imperfect or double <br> cleavage into irregular often somewhat prismatic fragments Fre- <br> quently however these beds have especiall - where much weathered <br> a pale grey colour much resembling that of the beds above the Grits <br> This may perhaps be because they are derived directly from the fel- <br> spathic ash of some volcanic district while the Silurian beds above <br> the Grits have been formed later on from the waste of such beds <br> These pale beds above the Grits pass up into the Pale Slates of <br> the Survey which in turn pass up into the striped flaggy Slates of <br> Penyglog on the top of which come Grits to be referred to the true <br> Denbigh Flag- and Grit-series and which I traced for about two miles <br> to the N side of Moel Ferna In the flaggy Slates I found Grapto- <br> lithus priodon Cyrtograpsus Murchisoni and JRetiolites sp with <br> Orthoceras pinmcevum and 0 subundulatum I again found some <br> Graptolites in a small watercourse N E of Moel Ferna on what <br> seemed to be the same horizon The dip is here about 10° ISLE to <br> N N E and the cleavage 30° N I would here acknowledge much <br> useful information which I got from Mr Phillips of the Penyglog <br> Quarries <br> I then tried to apply this key to other districts <br> First then there is a patch of Bala coming in south of the fault <br> near Bryn Gorlan at the south end of the Yale of Clwyd as shown <br> in the section fig 2 <br> Fig 2 Section at Bryn Gorlan Vale of Clwyd <br> N Llanfair- <br> dyffrynclwyd <br> i <br> Bryn <br> Gorlan <br> c ~ 7 e -f i tn Pit 7i- <br> a New Red b Basement bed of New Eed sometimes conglomeratic <br> c Carboniferous Sandstone generally stained red d Mountain Limestone <br> e Basement bed of Mountain Limestone shale sandstone and conglomerate <br> f Denbigh Flags <br> k Pale slates including part of what was previously called Bala <br> I Corwen Grit on Bala beds <br> Here I found at the north end the Denbigh Flags These may <br> be examined along the road to LlanfairdyfErynclwyd where Grapto- <br> lites chiefly G priodon occur South of the Bryn-Gorlan fault we <br> Q J G S No 130 p 35818328 110705 51125 Page 209 Text 33 http //www biodiversitylibrary org/page/35818328 1877 Geological Society of London NameFound Cyrtograpsus NameConfirmed Cyrtograpsus EOLID 4266530 NameBankID 4134941 NameFound Ferna NameConfirmed Ferna NameBankID 4459310 NameFound Graptolites NameConfirmed Graptolites NameBankID 423327 NameFound Graptolites priodon NameFound Orthoceras NameConfirmed Orthoceras EOLID 30106 NameBankID 1861424 Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 33 1877 Geology Periodicals Smithsonian Libraries bhl page 35818328 dc identifier http //biodiversitylibrary org/page/35818328 smithsonian libraries Information field Flickr posted date ISOdate 2014-02-24 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/12735780365 2015-08-26 19 54 52 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1877 Photos uploaded from Flickr by Fæ using a script | ||||
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