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| Keywords: The Quarterly journal of the Geological Society of London (13204791884).jpg 48 <br> J W E DAVID GLACIAL ACTION IN SOUTH <br> 1 <br> CO <br> imp <br> t <br> ¢\ 4 <br> 3 » <br> o § <br> – ” ¢ i» <br> ¢IH Q <br> Iff <br> +3 ' ' <br> 3 <br> As all the Boulder-clay in <br> Brecknockshire examined by the <br> author is unstratified it may be <br> provisionally assumed that it is the <br> product of land-ice From the <br> occurrence of undisturbed sheets <br> of Boulder-clay at the bottoms of <br> valleys as at Tstrad-fellte in the <br> Neath valley Pen-y-graig in the <br> Rhondda-fawr valley and St Fa- <br> gans and St George's in the Ely <br> valley it may be inferred that the <br> excavation of these valleys took <br> place at some time previous to the <br> final disappearance of the ice <br> 3 Shattered and contorted Bock- <br> surfaces and intrudedBoulder-clay <br> ” The rocks of South Brecknock- <br> shire and East Glamorganshire <br> which are soft and easily disjointed <br> are more often shattered and con- <br> torted than striated This is the <br> case in the Old Eed Sandstone <br> area south of the Beacons and <br> with many of the finely laminated <br> sandstones of the Coal-measures <br> and the Triassic and Liassic rocks <br> of the Ely valley <br> This shattering and contorting <br> of rock-surfaces is much more <br> common as an evidence of glacia- <br> tion in the coal-basin than the <br> grooving and striating of the sur- <br> face-rock It is to be met with <br> everywhere on the north north- <br> western and north-eastern slopes <br> of the Carboniferous-sandstone <br> hills In the Ely valley this rock- <br> shattering is particularly well <br> marked in the rocks belonging to <br> the Lower Lias formation At Ty- <br> fry near St Fagans there are seve- <br> ral roches moutonnees which illus- <br> trate the contorting and crushing <br> power of ice and the intrusion of <br> Boulder- clay At Ty-fry where <br> a quarry has been opened in two <br> of these roches moutonnees the <br> rock has been so much crushed as <br> to form a fine angular breccia 36928625 113681 51125 Page 48 Text 39 http //www biodiversitylibrary org/page/36928625 1883 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 39 1883 Geology Periodicals Smithsonian Libraries bhl page 36928625 dc identifier http //biodiversitylibrary org/page/36928625 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-16 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13204791884 2015-08-26 13 52 42 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1883 Photos uploaded from Flickr by Fæ using a script | ||||
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