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| Keywords: The Quarterly journal of the Geological Society of London (12736568934).jpg CHARACTER OF THE WHIN SILL OF NORTHUMBERLAND <br> 415 <br> the escarpment of basalt on the summit of which is built the Great <br> lloman Wall deserves special mention first as being an almost <br> unique example of its kind and 'secondly because oddly enough it <br> has been very inaccurately it is true figured by Hutton in the <br> very paper in which he proved to his satisfaction the contempo- <br> raneity of the Whin <br> A bed of limestone with an accompanying shale which has for <br> some distance from the west run regularly below the basalt and <br> parallel to it is here suddenly forced upwards almost vertically into <br> the Whin by which it is baked and altered in a very evident <br> manner Now where this limestone underlies the W T hin Sill the <br> latter is capped by sandstone ; but immediately after the disturbance <br> just described the limestone and shale are seen overlying the Whin <br> in place of the sandstone the outcrop of which however is in <br> nowise disturbed by the occurrence and can easily be traced run- <br> ning still parallel to but further above the trap-sheet <br> This is merely a case of the Whin Sill being seen actually in the <br> act flagrante delicto of shifting its horizon ; but it has this <br> further interest that it proves that at this point the molten mass <br> was forcing itself from east to west the change having necessarily <br> been from a lower to a higher horizon This may have been but a <br> local direction due to the mass having to circumvent obstacles in <br> its progress or to some other cause ; but there are some reasons <br> g the bifurcation to the N E the generally greater thickness <br> in that direction c which would lead us to imagine that this is <br> but a part of a general truth with regard to the position of the <br> original focus of the Great- Whin eruption <br> Although as a rule it may be said that the upper surface of the <br> Whin is tolerably smooth yet there are many instances of isolated <br> masses both great and small having been thrust up from the main <br> sheet to a greater or less distance through the overlying beds The <br> eastern branch important as it is must we think be looked upon <br> as an extreme case of this kind ; and between it and small bosses a <br> few yards only in diameter appearing as little islands through thin <br> layers of limestone capping the Whin of which there are very nu- <br> merous examples on the dip-slope of Gunnerton Crags fig 5 at Great <br> Fig 5 ” Section at Gunnerton Crags showing the upper surface of <br> the main or western branch of the Whin Sill protruding through <br> the overlying Limestone <br> B Whin Sill <br> GAL <br> L Limestone 35818558 110705 51125 Page 415 Text 33 http //www biodiversitylibrary org/page/35818558 1877 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 33 1877 Geology Periodicals Smithsonian Libraries bhl page 35818558 dc identifier http //biodiversitylibrary org/page/35818558 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 N02/12736568934 2015-08-26 19 52 53 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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