﻿PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  655 
  

  

  of 
  this 
  spot. 
  The 
  purple 
  mudstones 
  of 
  the 
  " 
  G.-Orayi 
  bed" 
  which 
  

   caps 
  the 
  Penkill-shale 
  group 
  of 
  that 
  locality 
  are 
  succeeded 
  to 
  the 
  

   northward 
  by 
  scattered 
  exposures 
  of 
  pale 
  jointed 
  flagstone 
  with 
  

   shale-partings, 
  identical 
  with 
  the 
  flagstones 
  of 
  Penwhapple 
  Glen- 
  

   foot. 
  These 
  Glenfoot 
  flags 
  extend 
  down 
  the 
  stream 
  for 
  a 
  distance 
  

   of 
  about 
  200 
  yards, 
  and 
  agree 
  therefore 
  in 
  collective 
  thickness 
  with 
  

   their 
  counterparts 
  of 
  the 
  glen. 
  

  

  Between 
  them 
  and 
  the 
  great 
  Bargany 
  fault 
  to 
  the 
  northward, 
  

   which 
  is 
  shown 
  in 
  a 
  section 
  of 
  great 
  interest 
  in 
  Blackwood 
  Head 
  

   coppice, 
  is 
  found 
  an 
  equal 
  thickness 
  of 
  grey, 
  flaggy 
  shales 
  or 
  muddy 
  

   flagstones. 
  Many 
  of 
  these 
  have 
  the 
  same 
  pale-coloured 
  interior 
  as 
  

   the 
  Glenfoot 
  beds 
  ; 
  but 
  they 
  are 
  altogether 
  a 
  more 
  finely 
  laminated 
  

   group, 
  showing 
  no 
  actual 
  greywacke 
  zones 
  at 
  this 
  spot, 
  but 
  only 
  

   occasional 
  harder 
  ribs. 
  They 
  are 
  beautifully 
  shown 
  in 
  the 
  cliffs 
  of 
  

   the 
  little 
  glen 
  dug 
  out 
  by 
  the 
  burn, 
  at 
  the 
  waterfall 
  near 
  the 
  Bargany 
  

   fault, 
  where 
  they 
  are 
  seen 
  in 
  contact 
  with 
  the 
  Carboniferous 
  of 
  the 
  

   Girvan 
  valley. 
  They 
  are 
  frequently 
  striped 
  with 
  faint 
  lines 
  of 
  car- 
  

   bonaceous 
  matter, 
  suggestive 
  of 
  the 
  presence 
  of 
  Graptolites, 
  a 
  few 
  of 
  

   which 
  are 
  obtainable 
  at 
  this 
  spot, 
  such 
  as 
  

  

  Monograptus 
  acus, 
  Lapw. 
  | 
  Monograptus 
  priodon, 
  Bronn. 
  

  

  The 
  next 
  stream-course 
  to 
  the 
  eastward, 
  which 
  excavates 
  a 
  small 
  

   gorge 
  on 
  the 
  opposite 
  side 
  of 
  the 
  wood, 
  presents 
  us 
  with 
  a 
  section 
  of 
  

   parts 
  of 
  the 
  Glenfoot 
  flags 
  and 
  these 
  shalier 
  Blackwood-Head 
  beds. 
  

   The 
  Glenfoot 
  beds 
  exposed 
  are 
  especially 
  interesting, 
  as 
  they 
  are 
  

   higher 
  in 
  the 
  group 
  than 
  the 
  majority 
  of 
  those 
  we 
  have 
  studied 
  in 
  

   Penwhapple 
  Glen. 
  The 
  final 
  band 
  is 
  seen 
  to 
  contain 
  several 
  seams 
  of 
  

   sandy 
  greywacke 
  of 
  a 
  pale 
  purplish 
  colour, 
  while 
  the 
  intermediate 
  

   shales 
  have 
  a 
  peculiar 
  greyish-green 
  or, 
  as 
  it 
  were, 
  washed-out 
  tint, 
  

   and 
  a 
  dull 
  flaky 
  surface, 
  which 
  is 
  new 
  among 
  the 
  beds 
  hitherto 
  met 
  

   with 
  in 
  the 
  Girvan 
  succession. 
  

  

  The 
  lowest 
  ribbed 
  shales 
  of 
  the 
  Blackwood-Head 
  beds 
  are 
  shown 
  in 
  

   two 
  fine 
  quarries, 
  and 
  form 
  a 
  most 
  conspicuous 
  assemblage 
  of 
  about 
  

   150 
  feet 
  of 
  dull 
  greyish-brown 
  rocks 
  in 
  beds 
  of 
  about 
  2 
  inches 
  in 
  

   thickness. 
  

  

  A. 
  few 
  feet 
  of 
  the 
  higher 
  striped 
  shales 
  are 
  seen 
  to 
  the 
  northward, 
  

   close 
  to 
  the 
  line 
  of 
  fault. 
  

  

  In 
  the 
  small 
  hollow 
  of 
  the 
  Lime 
  Glen, 
  three 
  fourths 
  of 
  a 
  mile 
  

   further 
  to 
  the 
  eastward, 
  the 
  pale-hearted 
  finely 
  levigated 
  sandstone 
  

   flags 
  of 
  Blackwood-Head 
  occur 
  in 
  a 
  broken 
  section 
  in 
  the 
  neighbour- 
  

   hood 
  of 
  the 
  Bargany 
  fault. 
  So 
  far 
  as 
  can 
  be 
  made 
  out 
  upon 
  the 
  

   ground, 
  they 
  here 
  consist 
  of 
  three 
  distinct 
  lithological 
  seams, 
  viz. 
  

  

  (c) 
  Yellow-weathering 
  mudstone 
  flags, 
  pale-hearted, 
  white 
  

  

  or 
  bluish 
  grey. 
  

   (6) 
  Yellow-weathering 
  mudstone 
  flags 
  with 
  stripes 
  of 
  

  

  carbonaceous 
  matter. 
  

   (a) 
  Pale-green 
  ribbed 
  shales 
  and 
  mudstones. 
  

  

  The 
  white-hearted 
  mudstone 
  flags 
  (c) 
  are 
  seen 
  also 
  in 
  Currah 
  Glen. 
  

   In 
  some 
  neglected 
  quarries 
  below 
  the 
  rugged 
  cliff 
  to 
  the 
  south-west 
  

  

  