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| Keywords: The Quarterly journal of the Geological Society of London (13204723485).jpg 290 <br> A GKEIEIE OJS THE SUPPOSED <br> Fig 8 Section showing the Interstratification of Tuff and <br> Conglomerate above Lower Mill St David's <br> '- jggg u <br> The conglomerate as there exposed is regularly interstratified with <br> tuff The beds are vertical On the left side of the little quarry as <br> we enter it layers of fine reddish tuff a are succeeded by a band <br> of quartz conglomerate 6 of the usual character Parallel to this <br> conglomerate comes a band about six inches thick of fine tuff c <br> followed by ashy sandstone d which graduates into conglome- <br> rate e No more complete evidence could be desired of the perfect <br> inosculation of the conglomerate with the volcanic group On the <br> coast at Nun's Chapel similar evidence presents itself The con- <br> glomerate there contains some thin seams of tuff and is intercalated <br> between a series of dull green agglomerates and tuffs and some <br> greenish shales and sandstones with layers of tuff <br> There is evidence that though volcanic action became dormant or <br> at least exceedingly feeble in the interval immediately succeeding <br> that in which the conglomerate was laid down it reappeared at a <br> later part of the Cambrian period Thus about three miles east from <br> St David's on the road south from Pelin-canot near Whitchurch <br> beds of volcanic tuff may be seen overlying Cambrian grits Again <br> in a deep valley Cwm Mawr between Pointz Castle and Newgale <br> Bridge on the coast six miles east from St David's a coarse <br> volcanic tuff or agglomerate and ashy sandstone is interstratified in <br> beds which must be high up in the Lower Cambrian formation <br> certainly far above any of the beds near St David's This rock <br> presents petrographical characters somewhat different from those of <br> the tuffs in the volcanic group above described see Part II These <br> intercalations which were noticed by Mr Peach and myself as we <br> passed the localities show that occasional eruptions took place <br> during the deposition of later stages of the Cambrian groups A <br> more exhaustive search of the whole region would doubtless bring <br> to light other volcanic zones on different horizons and enable us to <br> connect the volcanic episode of St David's with that of the Lower <br> Silurian period in North Pembrokeshire <br> It follows from the facts now detailed that the volcanic group of <br> Red tuff of precisely the same character conformably underlies the con- <br> glomerate on the east side of the fold above Caerbwdy Mill 36928889 113681 51125 Page 290 Text 39 http //www biodiversitylibrary org/page/36928889 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 36928889 dc identifier http //biodiversitylibrary org/page/36928889 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 N02/13204723485 2015-08-26 13 54 37 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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