﻿PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  

  

  585 
  

  

  S.E. 
  

  

  Fig. 
  14. 
  — 
  Typical 
  Section 
  near 
  Balclatchie 
  Bridge. 
  

  

  N.W. 
  

  

  Ba. 
  Ardwell 
  Graptolitic 
  Shales 
  and 
  Flags. 
  

  

  a 
  1 
  . 
  Dark 
  carbonaceous 
  and 
  iron-stained 
  shales, 
  with 
  Graptolites. 
  

   (n) 
  Basal 
  zone 
  of 
  calcareous 
  and 
  carbonaceous 
  shales, 
  with 
  Climacograptus 
  

   Scharenbergi, 
  Lasiograptus 
  HarJcnessi, 
  and 
  Cryptograptits 
  tricornis. 
  

   Ad 
  2 
  . 
  Balclatchie 
  Grits 
  and 
  Conglomerate. 
  

  

  d 
  2 
  '". 
  Ashy 
  gritstones 
  and 
  flaggy 
  beds, 
  fossiliferous. 
  

   d 
  2 
  ". 
  Calcareous 
  boulder 
  conglomerate, 
  with 
  Lingula 
  canadensis. 
  

   d 
  2 
  '. 
  Green 
  flaggy 
  gritstones, 
  calcareous, 
  fossiliferous. 
  

   Ad 
  1 
  . 
  Balclatchie 
  Shales. 
  

  

  Grey 
  and 
  green 
  calcareous 
  and 
  nodular 
  mi 
  idstones, 
  highly 
  fossiliferous 
  — 
  

   with 
  Barrandia, 
  Remopleurides 
  laterispinifer 
  , 
  Ampyx 
  Hornei, 
  Asapkus 
  

   gigas, 
  Siphonotreta 
  micula, 
  Bicranograptus 
  tardwscidus, 
  &c. 
  

   Ac. 
  Benan 
  Conglomerate. 
  

  

  Coarse 
  conglomerate 
  and 
  interbedded 
  sandstones, 
  with 
  boulders 
  of 
  quartz 
  

  

  and 
  felsite. 
  

   *, 
  *, 
  *. 
  Basaltic 
  dykes. 
  

  

  teristic 
  features. 
  Boulders 
  of 
  quartz, 
  granite 
  and 
  felstone, 
  often 
  of 
  

   large 
  size, 
  are 
  confusedly 
  huddled 
  together 
  in 
  a 
  greenish 
  matrix 
  

   composod 
  of 
  a 
  sandy 
  or 
  more 
  or 
  less 
  ashy 
  material, 
  which 
  weathers 
  

   on 
  the 
  surface 
  to 
  a 
  dull 
  orange 
  tint. 
  Its 
  highest 
  beds 
  are 
  well 
  ex- 
  

   posed 
  in 
  some 
  small 
  cliffs 
  that 
  overhang 
  the 
  roadway 
  to 
  the 
  north 
  

   of 
  the 
  bridge, 
  where 
  they 
  exhibit 
  distinct 
  evidence 
  of 
  their 
  bedded 
  

   nature 
  in 
  the 
  visible 
  arrangement 
  of 
  the 
  rounded 
  balls 
  of 
  white 
  

   quartz 
  and 
  grey 
  porphyrite 
  in 
  regularly 
  parallel 
  lines, 
  and 
  in 
  the 
  

   distinct 
  alternation 
  of 
  coarse 
  conglomeratic 
  bands 
  with 
  others 
  of 
  a 
  

   sandier 
  texture. 
  These 
  all 
  dip 
  steadily 
  to 
  the 
  northward, 
  at 
  an 
  

   angle 
  of 
  from 
  50 
  to 
  60 
  degrees, 
  and 
  distinctly 
  follow 
  each 
  other 
  in 
  

   unbroken 
  sequence. 
  

  

  The 
  highest 
  beds 
  of 
  the 
  conglomerate 
  proper 
  can 
  be 
  studied 
  foot 
  

   by 
  foot 
  in 
  these 
  cliffs. 
  Towards 
  their 
  termination 
  they 
  become 
  

   somewhat 
  looser 
  in 
  texture, 
  and 
  the 
  matrix 
  of 
  the 
  rock 
  grows 
  more 
  

   sandy. 
  At 
  their 
  summit, 
  where 
  they 
  are 
  pierced 
  by 
  three 
  small 
  

   basaltic 
  dykes 
  of 
  a 
  most 
  interesting 
  character, 
  they 
  pass 
  up 
  con- 
  

   formably 
  into 
  an 
  overlying 
  group 
  (the 
  Balclatchie 
  Beds, 
  Ad) 
  of 
  

   calcareous 
  shales 
  and 
  mudstones 
  and 
  flaggy 
  grits, 
  highly 
  fossiliferous. 
  

   The 
  unbroken 
  continuity 
  of 
  the 
  sequence 
  at 
  this 
  locality 
  is 
  easily 
  

   demonstrated. 
  The 
  pebble-beds 
  characteristic 
  of 
  the 
  Benan 
  Con- 
  

   glomerate 
  below, 
  and 
  the 
  shaly 
  beds 
  characteristic 
  of 
  the 
  Balclatchie 
  

   zone 
  above, 
  distinctly 
  alternate 
  with 
  each 
  other 
  in 
  a 
  curious 
  group 
  

  

  Q.J.G.S. 
  No. 
  152. 
  2r 
  

  

  