﻿PROP. 
  0. 
  LAPW0RTH 
  ON 
  THE 
  GIRVAJST 
  SUCCESSION. 
  617 
  

  

  (ii.) 
  Trinucleus-Mudstones 
  of 
  Drummuck. 
  

  

  Round 
  three 
  fourths 
  of 
  the 
  superficies 
  of 
  the 
  anticlinal 
  dome 
  of 
  

   Quarrel 
  Hill 
  the 
  Barren 
  Flagstones 
  are 
  succeeded 
  by 
  the 
  highly 
  fossi- 
  

   liferous 
  group 
  of 
  dark 
  mudstones 
  which 
  I 
  term, 
  the 
  Drummuck 
  Beds. 
  

   In 
  mineral 
  aspect 
  and 
  in 
  fossils 
  they 
  remind 
  us 
  strongly 
  of 
  some 
  of 
  

   the 
  zones 
  of 
  the 
  Whitehouse 
  shales 
  (Bb) 
  that 
  immediately 
  underlie 
  

   the 
  Barren-flagstone 
  series 
  ; 
  but 
  they 
  contain 
  none 
  of 
  the 
  brilliantly 
  

   coloured 
  mudstones 
  of 
  that 
  group, 
  nor 
  any 
  of 
  the 
  beautifully 
  striped 
  

   and 
  banded 
  shales 
  which 
  it 
  possesses 
  in 
  common 
  with 
  the 
  older 
  Ard- 
  

   well 
  group. 
  The 
  physical 
  relations 
  of 
  the 
  Barren 
  Flags 
  and 
  these 
  

   overlying 
  Trinudeus- 
  mudstones 
  are 
  best 
  displayed 
  in 
  the 
  flanks 
  of 
  

   Quarrel 
  Hill 
  ; 
  but 
  the 
  finest 
  and 
  most 
  prolific 
  sections 
  of 
  the 
  latter 
  

   group 
  are 
  shown 
  to 
  the 
  north, 
  along 
  the 
  course 
  of 
  the 
  Lady 
  Burn, 
  

   and 
  in 
  the 
  neighbourhood 
  of 
  the 
  farm 
  of 
  Drummuck, 
  which 
  gives 
  

   its 
  name 
  to 
  the 
  subformation. 
  

  

  The 
  superposition 
  of 
  these 
  fossiliferous 
  mudstones 
  to 
  the 
  Barren- 
  

   flagstone 
  group 
  will 
  at 
  once 
  be 
  understood 
  from 
  the 
  following 
  

   section 
  (fig. 
  21, 
  p. 
  618), 
  which 
  is 
  carried 
  in 
  an 
  easterly 
  direction 
  along 
  

   the 
  anticlinal 
  axis 
  from 
  Balweary 
  Wood 
  to 
  Mulloch 
  Hill. 
  Indeed 
  the 
  

   disposition 
  of 
  the 
  several 
  zones 
  of 
  strata 
  which 
  here 
  cross 
  over 
  the 
  

   anticlinal, 
  as 
  developed 
  in 
  the 
  mapping 
  of 
  the 
  area, 
  make 
  this 
  so 
  

   clear 
  and 
  unequivocal 
  that 
  no 
  further 
  proof 
  of 
  their 
  relationship 
  is 
  

   necessary 
  in 
  this 
  place. 
  

  

  1. 
  Quarrel 
  Hill. 
  — 
  The 
  lowest 
  strata 
  I 
  assign 
  to 
  the 
  Drummuck 
  Beds 
  

   are 
  a 
  group 
  of 
  thick-bedded 
  flagstones, 
  filled 
  with 
  pebbles 
  of 
  quartz, 
  

   and 
  separated 
  by 
  seams 
  of 
  grey 
  and 
  green 
  shales, 
  both 
  rocks 
  containing 
  

   a 
  notable 
  proportion 
  of 
  carbonate 
  of 
  lime. 
  They 
  are 
  exposed 
  in 
  a 
  

   steep 
  escarpment 
  at 
  the 
  summit 
  of 
  Quarrel 
  Hill, 
  dipping 
  off 
  the 
  Barren 
  

   Flagstones 
  and 
  plunging 
  below 
  the 
  area 
  occupied 
  by 
  the 
  main 
  mass 
  

   of 
  the 
  Drummuck 
  Beds. 
  From 
  this 
  point, 
  as 
  will 
  be 
  seen 
  from 
  the 
  

   map 
  (PI. 
  XXV. 
  4), 
  they 
  may 
  be 
  followed 
  foot 
  by 
  foot, 
  occupying 
  the 
  

   same 
  stratigraphical 
  place 
  in 
  the 
  succession, 
  through 
  the 
  converging 
  

   dislocations 
  of 
  Quarrel 
  Hill, 
  circling 
  round 
  parallel 
  with 
  the 
  overlying 
  

   and 
  underlying 
  zones, 
  till 
  they 
  are 
  finally 
  cut 
  out 
  by 
  a 
  branch 
  of 
  the 
  

   Craighead 
  fault 
  to 
  the 
  south-west 
  of 
  the 
  old 
  ruin 
  of 
  Auldthorns. 
  

  

  These 
  pebbly 
  flagstones 
  have 
  a 
  collective 
  thickness 
  of 
  about 
  50 
  

   or 
  60 
  feet, 
  and 
  abound 
  in 
  casts 
  of 
  fossils 
  of 
  the 
  same 
  general 
  

   facies 
  as 
  those 
  characteristic 
  of 
  the 
  overlying 
  mudstones. 
  The 
  com- 
  

   monest 
  forms 
  are 
  Leptcena 
  sericea 
  and 
  Strophomena. 
  

  

  The 
  finer 
  strata 
  which 
  succeed 
  to 
  these 
  basal 
  flagstones 
  are 
  well 
  

   displayed 
  in 
  the 
  numerous 
  stream-courses 
  that 
  descend 
  the 
  eastern 
  

   flanks 
  of 
  Quarrel 
  Hill. 
  Their 
  upper 
  boundary 
  is 
  strikingly 
  de- 
  

   fined 
  by 
  a 
  mass 
  of 
  purple 
  conglomerate, 
  which 
  forms 
  the 
  base 
  of 
  an 
  

   overlying 
  group, 
  and 
  ranges 
  through 
  the 
  faulted 
  areas 
  strictly 
  

   parallel 
  with 
  the 
  basal 
  flagstones 
  last 
  noticed. 
  In 
  the 
  area 
  thus 
  

   limited, 
  we 
  find 
  a 
  great 
  thickness 
  of 
  mudstones 
  and 
  shales 
  of 
  a 
  

   greyish-blue 
  colour, 
  very 
  rarely 
  interrupted 
  by 
  thin 
  seams 
  of 
  greenish- 
  

   grey 
  flagstone 
  or 
  greywacke. 
  The 
  lowest 
  beds 
  are 
  hard 
  shales, 
  of 
  

   tough 
  texture, 
  weathering 
  down 
  into 
  conchoidal 
  flakes. 
  Higher 
  up 
  

  

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

  

  