﻿PKOF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  623 
  

  

  There 
  is 
  no 
  actual 
  proof 
  of 
  an 
  unconformity 
  between 
  the 
  Drum- 
  

   muck 
  mudstones 
  and 
  this 
  conglomerate 
  ; 
  but 
  the 
  change 
  in 
  mineralo- 
  

   gies! 
  character 
  from 
  a 
  soft 
  laminated 
  mudstone 
  to 
  massive 
  boulder- 
  

   beds 
  and 
  sandstones 
  is 
  proof 
  of 
  a 
  complete 
  modification 
  of 
  the 
  

   physical 
  features 
  of 
  the 
  neighbouring 
  sea-bed 
  between 
  the 
  periods 
  

   of 
  deposition 
  of 
  these 
  highly 
  dissimilar 
  sediments, 
  and 
  the 
  great 
  

   alteration 
  in 
  the 
  aspect 
  of 
  the 
  fauna, 
  caused 
  by 
  the 
  disappearance 
  

   of 
  many 
  prominent 
  genera 
  and 
  species, 
  is 
  sufficient 
  proof 
  that 
  the 
  

   intervening 
  period 
  was 
  of 
  great 
  geological 
  importance. 
  

  

  (Ca2) 
  Mullock-Hill 
  Sandstones. 
  — 
  This 
  purple 
  conglomerate 
  of 
  

   Quarrel 
  Hill 
  graduates 
  upwards 
  into 
  a 
  mass 
  of 
  soft 
  sandstones, 
  at 
  

   least 
  250 
  feet 
  in 
  thickness, 
  which, 
  because 
  of 
  their 
  typical 
  exhibition 
  

   on 
  the 
  summit 
  and 
  flanks 
  of 
  Mulloch 
  or 
  Kirk 
  Hill, 
  I 
  shall 
  refer 
  to 
  as 
  

   the 
  Mulloch-Hill 
  sandstones. 
  They 
  are 
  shown 
  in 
  a 
  large 
  number 
  

   of 
  open 
  quarries 
  along 
  the 
  hill-road 
  north-east 
  of 
  High 
  Mains, 
  and 
  

   thence 
  for 
  some 
  distance 
  along 
  the 
  same 
  road 
  almost 
  to 
  the 
  steading 
  

   of 
  High 
  jSTewlands. 
  A 
  fine 
  display 
  of 
  the 
  same 
  beds 
  is 
  seen 
  in 
  the 
  

   old 
  quarry 
  at 
  Hough 
  Neuk; 
  and 
  they 
  are 
  easily 
  studied 
  in 
  situ 
  in 
  the 
  

   courses 
  of 
  the 
  many 
  burns 
  that 
  descend 
  the 
  flanks 
  of 
  Quarrel 
  Hill. 
  

   In 
  all 
  these 
  localities 
  they 
  retain 
  the 
  same 
  general 
  facies 
  of 
  a 
  thick- 
  

   bedded 
  series 
  of 
  sandstones 
  separated 
  by 
  thin 
  seams 
  of 
  sandy 
  shales. 
  

   The 
  natural 
  colour 
  of 
  the 
  rock 
  is 
  a 
  dark 
  grey, 
  with 
  a 
  slight 
  greenish 
  

   tinge 
  ; 
  but 
  when 
  weathered 
  it 
  becomes 
  gradually 
  coated 
  with 
  an 
  

   exterior 
  tint 
  of 
  purple 
  or 
  yellowish 
  red, 
  which 
  soon 
  extends 
  itself 
  

   inwards 
  till 
  finally 
  the 
  entire 
  rock 
  becomes 
  of 
  a 
  deep 
  rusty 
  or 
  

   iron-shot 
  colour. 
  

  

  These 
  sandstones 
  are 
  soft 
  and 
  sectile, 
  breaking 
  up 
  easily 
  under 
  

   the 
  hammer. 
  The 
  more 
  flaggy 
  beds 
  have 
  usually 
  a 
  rough 
  conchoidal 
  

   fracture 
  ; 
  the 
  thicker 
  sandstones 
  split 
  up 
  much 
  more 
  evenly, 
  and 
  

   generally 
  weather 
  down 
  into 
  rough 
  tilestones. 
  The 
  shaly 
  alterna- 
  

   tions 
  rarely 
  show 
  evidence 
  of 
  regular 
  lamination, 
  but 
  fall 
  away 
  in 
  

   rough 
  and 
  irregular 
  flakes. 
  

  

  The 
  whole 
  mass 
  of 
  beds 
  retains 
  very 
  much 
  the 
  same 
  mineralogical 
  

   character 
  from 
  base 
  to 
  summit 
  ; 
  but 
  in 
  the 
  lower 
  zones 
  sandstones 
  

   are 
  broadly 
  preponderant. 
  The 
  highest 
  zone 
  of 
  the 
  group 
  is 
  actually 
  

   a 
  band 
  of 
  pale 
  yellow 
  sandstones. 
  It 
  passes 
  upwards 
  conformably 
  

   into 
  a 
  superior 
  group 
  of 
  yellow-weathermg 
  mudstones 
  (Cb3), 
  which, 
  

   as 
  seen 
  on 
  Mulloch 
  Hill, 
  are 
  comparatively 
  barren. 
  A 
  few 
  Brachio- 
  

   poda 
  and 
  species 
  of 
  Ptiloc/rajjtus 
  occur 
  in 
  the 
  exposures 
  N.E. 
  of 
  Kirk 
  

   Hill, 
  near 
  the 
  cottage 
  of 
  High 
  Newlands. 
  

  

  The 
  Mulloch-Hill 
  sandstones 
  range 
  southeastwards 
  from 
  the 
  

   typical 
  localities 
  obliquely 
  down 
  the 
  slopes 
  of 
  High 
  Mains 
  into 
  the 
  

   low-lying 
  flat 
  of 
  the 
  Quarrel 
  Burn, 
  below 
  the 
  ruins 
  of 
  Auldthorns. 
  

   They 
  are 
  much 
  cut 
  up 
  by 
  the 
  many 
  loop-faults 
  of 
  that 
  complicated 
  

   area, 
  and 
  are 
  finally 
  inverted 
  and 
  pinched 
  out, 
  by 
  the 
  converging 
  

   faults 
  of 
  Quarrel 
  Hill 
  and 
  Craighead, 
  near 
  Kildrummie. 
  In 
  the 
  

   streams 
  and 
  exposures 
  of 
  the 
  area 
  occupied 
  by 
  these 
  beds 
  below 
  

   Auldthorns 
  the 
  strata 
  are 
  crowded 
  with 
  fossils. 
  They 
  are 
  fully 
  as 
  

   abundant 
  as 
  upon 
  Mulloch 
  Hill, 
  and 
  are 
  occasionally 
  even 
  more 
  

   completely 
  preserved. 
  

  

  