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| Keywords: The Quarterly journal of the Geological Society of London (13365232955).jpg 258 PROCEEDINGS OF THE GEOLOGICAL SOCIETY Jan 23 <br> Fig 3 Section at Pebble Hill <br> Ochreous gravel composed chiefly of round flint pebbles <br> London clay; blackish sandy clay passing downwards into <br> brown clay; round flint pebbles and very friable shells <br> dispersed irregularly throughout <br> Coarse ferruginous sand fuU of round flint pebbles 1 to 12 <br> inches in diameter ; some chalk pebbles ; many of the flint <br> pebbles decomposed throughout into a white friable struc- <br> ture This bed frequently passes into an iron sandstone <br> conglomerate <br> d Blottled clays chiefly of a light greenish colour overlying an <br> irregular bed of sand below which succeed other irregular <br> beds of mottled clays <br> The chalk crops out about 6o feet below c <br> Stratum c here contains no organic remains except the teeth <br> of the same species of Lamnce which occur at Clarendon Hill and <br> which we shall find to accompany this hed very constantly in the <br> London district This point forms the apex of a long and roughly <br> triangular area occupied by the tertiary eocene strata and stretching <br> eastward to the German Ocean The southern side of this triangle <br> extends from Pebble Hill to the cliff near the Reculvers in Kent a <br> distance of about 1 00 miles and the northern side from Pebble Hill <br> to Woodbridge in Suffolk nearly 140 miles Owing to the thickness <br> of the London clay in the tract between these two lines it is only <br> by well-sections that we can learn anything of its basement bed If <br> however we follow the outcrop of the beds we shall find this stratum <br> coming to the surface with much regularity along the southern edge <br> of the tertiary area whilst along its northern edge it forms a more <br> broken and irregular line This arises from the tertiary deposits being <br> on the south from Inkpen to Croydon tilted up at a considerable <br> angle against the ridge of chalk hills which throws them out sud- <br> denly and sharply whereas towards the north they rise gradually <br> and form with the chalk a tolerably regularly inclined plane from their <br> outcrop from below the London clay to the edge of the chalk escarp- <br> ment disappearing only gradually according as the chalk attains <br> a higher level and adapting themselves to all the irregularities and <br> variations of the surface <br> On this latter side therefore the tertiary strata often form hills <br> overlooking the chalk district whilst on the south side the chalk <br> hills almost constantly command fine and extensive views over the <br> tertiary area <br> In following the basement bed of the London clay eastward from <br> Pebble Hill it will be convenient to take these two sides of the <br> triangle separately It happens that many of the beds between the <br> chalk and the London clay are of considerable economical value for <br> their sands and tile and pottery clays and they are consequently <br> worked to a great extent A zone of brick and tile fields in fact <br> marks their outcrop from Marlborough to Ewell on the one side and <br> to Woodbridge on the other We are thus furnished with a series <br> of sections such as we obtain in no other part of the English ter- 36934113 113689 51125 Page 258 Text v 6 http //www biodiversitylibrary org/page/36934113 1850 Geological Society of London Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 6 1850 Geology Periodicals Smithsonian Libraries bhl page 36934113 dc identifier http //biodiversitylibrary org/page/36934113 smithsonian libraries Information field Flickr posted date ISOdate 2014-03-23 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/13365232955 2015-08-26 11 59 32 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1850 Photos uploaded from Flickr by FĂŚ using a script | ||||
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