﻿106 
  

  

  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Dec. 
  2, 
  

  

  Section 
  of 
  the 
  Avicula-contorta 
  Zone 
  at 
  Woodburn, 
  ten 
  miles 
  north- 
  

   east 
  of 
  Belfast. 
  

  

  No. 
  of 
  

   Bed. 
  

  

  Lithology. 
  

  

  Thickness. 
  

  

  Organic 
  Eemains. 
  

  

  1 
  

  

  2 
  

   3 
  

   4 
  

   5 
  

  

  Basalt, 
  about 
  

  

  ft. 
  in. 
  

   50 
  

  

  2 
  

  

  8 
  

  

  Avicula 
  contorta. 
  

   Axinus 
  cloacinus. 
  

  

  f 
  Scattered 
  Fish-remains, 
  

   \ 
  Avicula 
  contorta. 
  

  

  Breccia 
  of 
  crystalline 
  lime- 
  1 
  

  

  Unseen 
  

  

  Black 
  Shales 
  

  

  6 
  

  

  6 
  

  

  1 
  10 
  

   1 
  

  

  10 
  6 
  

  

  Argillaceous 
  Limestone 
  

  

  Black 
  Shales 
  

  

  Argillaceous 
  Limestone 
  

  

  Black 
  Shales, 
  thinly 
  laminated 
  1 
  

   and 
  highly 
  charged 
  with 
  I 
  

   red 
  oxide 
  of 
  iron 
  j 
  

  

  Grey 
  Marls 
  of 
  the 
  Keuper 
  below 
  

  

  13 
  5 
  

  

  The 
  Avicula-contorta 
  beds 
  are 
  thus 
  separated 
  at 
  Woodburn 
  by 
  10 
  

   feet 
  from 
  the 
  Basalt, 
  and 
  2 
  feet 
  of 
  this 
  is 
  composed 
  of 
  a 
  breccia 
  of 
  

   granular 
  saccharoid 
  marble. 
  The 
  thickness 
  of 
  the 
  Avicnla-contorta 
  

   series 
  cannot 
  therefore 
  be 
  more 
  than 
  the 
  maximum 
  thickness 
  of 
  this 
  

   formation, 
  as 
  measured 
  in 
  Colin 
  Glen. 
  

  

  Here 
  all 
  the 
  beds 
  superior 
  to 
  this 
  zone 
  have 
  evidently 
  been 
  denuded 
  

   since 
  the 
  deposition 
  of 
  the 
  Cretaceous 
  strata, 
  but 
  previous 
  to 
  the 
  

   outpouring 
  of 
  the 
  Basalt. 
  At 
  about 
  \ 
  of 
  a 
  mile 
  in 
  the 
  direction 
  of 
  the 
  

   dip 
  of 
  the 
  beds 
  the 
  Upper 
  Greensand 
  attains 
  its 
  usual 
  thickness 
  ; 
  but 
  

   the 
  "White 
  Limestone 
  (Hard 
  Chalk) 
  is 
  only 
  20 
  feet 
  thick. 
  I 
  find 
  again 
  

   the 
  Avicula-contorta 
  beds, 
  with 
  Micaceous 
  Sandstones, 
  resting 
  on 
  the 
  

   Keuper 
  Marls 
  ; 
  and 
  in 
  close 
  proximity 
  the 
  shales 
  of 
  the 
  Ehaetic 
  

   series 
  are 
  completely 
  porcellanized 
  by 
  the 
  intrusion 
  of 
  a 
  trap-dyke. 
  

  

  4. 
  Section 
  at 
  Whitehead, 
  14 
  miles 
  north-east 
  of 
  Belfast. 
  — 
  Erom 
  

   the 
  base 
  of 
  the 
  Hard 
  Chalk, 
  the 
  escarpment 
  at 
  Whitehead 
  is 
  occu- 
  

   pied 
  by 
  an 
  underclifF 
  of 
  slipped 
  Triassic, 
  Liassic, 
  Gault, 
  and 
  Green- 
  

   sand 
  rocks. 
  In 
  the 
  railway 
  -cutting 
  through 
  this 
  undercliff 
  the 
  fol- 
  

   lowing 
  section 
  is 
  seen. 
  Little 
  reliance 
  can 
  be 
  placed 
  on 
  any 
  further 
  

   measurements, 
  from 
  the 
  veiy 
  disturbed 
  nature 
  of 
  the 
  slip. 
  

  

  Section 
  of 
  the 
  Avicula-contorta 
  Zone 
  at 
  Whitehead. 
  

  

  ft. 
  

  

  1. 
  Argillaceous 
  Limestone 
  

  

  2. 
  Black 
  Shales 
  3 
  

  

  3. 
  Compact 
  Shales 
  with 
  Axinus 
  cloacinus 
  and 
  

  

  Avicula 
  contorta 
  . 
  1 
  

  

  4. 
  Argillaceous 
  Limestone 
  

  

  5. 
  Black 
  Shales 
  6 
  

  

  6. 
  Argillaceous 
  Limestone 
  

  

  in. 
  

   3 
  

   

  

  u 
  

  

  