﻿572 
  PEOE. 
  C. 
  LAP 
  WORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  

  

  naif 
  a 
  mile 
  in 
  breadth, 
  occur 
  patches 
  of 
  limestones, 
  felspathic 
  grits 
  

   and 
  breccias, 
  and 
  bedded 
  igneous 
  rocks, 
  all 
  intensely 
  crumpled 
  and 
  

   crushed 
  together, 
  and 
  pierced 
  by 
  dykes 
  of 
  diorite 
  and 
  serpentine. 
  

   This 
  area 
  is 
  limited 
  by 
  faults 
  both 
  on 
  the 
  north 
  and 
  south, 
  outside 
  

   of 
  which 
  lie 
  the 
  unaltered 
  beds 
  of 
  the 
  Benan 
  Conglomerate. 
  

  

  On 
  both 
  margins 
  of 
  the 
  area 
  we 
  find 
  the 
  beds 
  of 
  the 
  calcareous 
  

   series 
  ; 
  and 
  the 
  general 
  disposition 
  of 
  the 
  greatly 
  wrinkled 
  strata 
  is 
  

   that 
  of 
  an 
  irregular 
  anticlinal. 
  

  

  Shalloch 
  Hill. 
  — 
  All 
  the 
  central 
  part 
  of 
  this 
  remarkable 
  area 
  is 
  

   formed 
  of 
  grey 
  and 
  purple 
  felsites, 
  breccias 
  of 
  igneous 
  rocks, 
  altered 
  

   shales, 
  and 
  a 
  peculiar 
  purple 
  brecciated 
  conglomerate. 
  This 
  last- 
  

   named 
  rock 
  forms 
  the 
  longitudinal 
  axis 
  of 
  the 
  area, 
  and 
  is 
  well 
  

   displayed 
  in 
  open 
  quarries 
  and 
  prominent 
  bosses 
  of 
  naked 
  rock. 
  

   Except 
  in 
  its 
  excessive 
  induration 
  and 
  the 
  presence 
  of 
  much 
  ser- 
  

   pentine 
  and 
  serpen 
  ti 
  nous 
  matter, 
  it 
  irresistibly 
  reminds 
  us 
  of 
  the 
  

   basal 
  conglomerate 
  (Aa 
  1 
  ) 
  of 
  Kirkland. 
  The 
  pebbles 
  of 
  igneous 
  rocks 
  

   enclosed 
  are 
  generally 
  smaller 
  than 
  those 
  of 
  the 
  Stinchar 
  rock 
  ; 
  but 
  

   the 
  brilliantly 
  purple 
  matrix, 
  highly 
  calcareous 
  and 
  traversed 
  by 
  

   innumerable 
  veins 
  of 
  spar, 
  is 
  identical. 
  

  

  The 
  associated 
  felsites, 
  breccias, 
  and 
  gabbros 
  are, 
  however, 
  most 
  

   distinctly 
  those 
  of 
  the 
  much 
  older 
  Ballantrae 
  Series, 
  in 
  which 
  cor- 
  

   responding 
  calcareous 
  breccias 
  (calcareous 
  and 
  serpentinous 
  ash- 
  

   beds) 
  occur 
  at 
  several 
  localities. 
  At 
  the 
  same 
  time 
  the 
  hardened 
  

   and 
  altered 
  rocks 
  of 
  the 
  present 
  area 
  are 
  fringed 
  to 
  the 
  N.W. 
  (see 
  

   plan, 
  fig. 
  8) 
  by 
  unaltered 
  breccias, 
  similar 
  to 
  those 
  of 
  Millenderdale, 
  

   which 
  lie 
  apparently 
  between 
  the 
  conglomerate 
  and 
  the 
  Ballantrae 
  

   Series. 
  I 
  am 
  therefore 
  inclined 
  to 
  the 
  opinion 
  that 
  the 
  whole 
  of 
  the 
  

   hardened 
  and 
  igneous 
  rocks 
  and 
  dykes 
  of 
  this 
  Shalloch-Hill 
  area 
  

   are 
  of 
  older 
  date 
  than 
  the 
  Kirkland 
  Purple 
  Conglomerate 
  (Aa 
  1 
  ), 
  and 
  

   are 
  here 
  brought 
  to 
  the 
  surface 
  along 
  a 
  faulted 
  anticlinal. 
  

  

  Nevertheless 
  there 
  are 
  difficulties 
  even 
  upon 
  this 
  theory 
  ; 
  for 
  cal- 
  

   careous 
  strata 
  belonging 
  to 
  the 
  Orthis-eonfinis 
  Flagstones 
  (Ab 
  1 
  ) 
  are 
  

   visibly 
  entangled 
  among 
  the 
  purple 
  beds 
  in 
  the 
  very 
  centre 
  of 
  the 
  

   area 
  and 
  afford 
  several 
  of 
  the 
  characteristic 
  fossils 
  in 
  a 
  fair 
  state 
  of 
  

   preservation. 
  They 
  are 
  even 
  better 
  exhibited 
  in 
  the 
  neighbourhood 
  

   of 
  the 
  Dupin 
  fault 
  near 
  the 
  edge 
  of 
  Auchenmaddy 
  Burn 
  on 
  its 
  

   north-east 
  margin, 
  where 
  Orthis 
  conjinis 
  and 
  Strophomena 
  alternata 
  

   are 
  not 
  uncommon. 
  

  

  4. 
  Little 
  Letterpin. 
  — 
  The 
  Craigwells 
  fault, 
  which 
  forms 
  the 
  northern 
  

   boundary 
  of 
  this 
  area, 
  is 
  prolonged 
  from 
  the 
  Shalloch 
  quarries 
  across 
  

   the 
  valley 
  of 
  the 
  Assel 
  into 
  the 
  elevated 
  ground 
  to 
  the 
  west 
  of 
  the 
  

   farm 
  of 
  Little 
  Letterpin, 
  where 
  the 
  limestone 
  was 
  formerly 
  worked 
  

   for 
  agricultural 
  purposes. 
  In 
  this 
  locality 
  we 
  have 
  a 
  repetition 
  in 
  

   miniature 
  of 
  the 
  phenomena 
  of 
  Shalloch 
  Hill. 
  The 
  limestone 
  seen 
  

   in 
  the 
  old 
  quarry 
  consists 
  merely 
  of 
  a 
  few 
  feet 
  of 
  very 
  impurely 
  

   calcareous 
  rock, 
  greatly 
  shattered, 
  dipping 
  irregularly 
  to 
  the 
  south- 
  

   ward, 
  and 
  faulted 
  abruptly 
  against 
  the 
  main 
  mass 
  of 
  Benan 
  Con- 
  

   glomerate 
  to 
  the 
  south. 
  The 
  higher 
  points 
  of 
  Little 
  Letterpin 
  Hill 
  

   consist 
  of 
  the 
  purple 
  grits 
  and 
  breccias 
  of 
  the 
  altered 
  series. 
  

  

  