﻿Haast. 
  — 
  On 
  the 
  Geological 
  Structure 
  of 
  Banks 
  Peninsula. 
  497 
  

  

  Thus 
  a 
  sub-marine 
  hill 
  stood 
  here 
  in 
  the 
  young 
  mesozoic 
  sea, 
  of 
  which 
  

   portions 
  of 
  the 
  summits 
  and 
  the 
  slopes 
  were 
  gradually 
  covered 
  by 
  agglo- 
  

   merates 
  and 
  brecciated 
  beds. 
  These 
  beds 
  were 
  formed 
  during 
  and 
  after 
  the 
  

   eruption 
  of 
  quartziferous 
  porphyries, 
  of 
  which 
  here 
  and 
  there 
  portions 
  of 
  

   the 
  coulees 
  have 
  been 
  preserved. 
  Some 
  of 
  these 
  quartziferous 
  porphyries 
  

   resemble 
  in 
  every 
  respect 
  those 
  from 
  the 
  Malvern 
  Hills 
  and 
  Mount 
  Somers. 
  

   They 
  are 
  also 
  accompanied 
  by 
  pitchstones, 
  porphyritic 
  from 
  the 
  presence 
  of 
  

   numerous 
  well-formed 
  crystals 
  of 
  sanidine 
  or 
  glassy 
  felspar, 
  and 
  occasionally 
  

   of 
  garnets. 
  Other 
  portions 
  of 
  the 
  quartziferous 
  porphyries, 
  as 
  for 
  instance, 
  

   the 
  whole 
  coulee 
  of 
  which 
  Manson's 
  Peninsula 
  is 
  formed, 
  have 
  a 
  rougher, 
  

   more 
  trachytic 
  matrix. 
  They 
  are 
  full 
  of 
  grains 
  and 
  small 
  crystals 
  of 
  white 
  

   greyish 
  or 
  smohy 
  quartz. 
  The 
  brecciated 
  beds 
  have 
  a 
  hard 
  felsitic 
  matrix, 
  

   and 
  the 
  angular 
  fragments 
  of 
  rock 
  enclosed 
  in 
  them 
  belong 
  to 
  a 
  variety 
  of 
  

   eruptive 
  rocks 
  of 
  many 
  colours, 
  and 
  of 
  different 
  texture, 
  often 
  forming 
  a 
  

   rock 
  of 
  striking 
  character. 
  They 
  appear 
  conspicuously 
  on 
  the 
  summit 
  of 
  

   Gebbie's 
  Pass, 
  having 
  been 
  washed 
  into 
  cliffs 
  of 
  picturesque 
  forms, 
  and 
  

   covering 
  the 
  palaeozoic 
  sedimentary 
  beds 
  from 
  one 
  side 
  of 
  the 
  pass 
  to 
  the 
  

   other. 
  After 
  the 
  formation 
  of 
  the 
  brecciated 
  agglomerates, 
  new 
  eruptions 
  

   of 
  acidic 
  rocks 
  took 
  place, 
  now 
  in 
  the 
  form 
  of 
  rhyolites, 
  the 
  highly 
  liquid 
  

   matter 
  reaching 
  the 
  surface 
  through 
  broad 
  channels, 
  of 
  which 
  one 
  has 
  been 
  

   preserved 
  as 
  a 
  large 
  dyke, 
  forming 
  a 
  beautiful 
  section 
  on 
  the 
  northern 
  side 
  

   of 
  Gebbie's 
  Pass, 
  not 
  far 
  from 
  the 
  summit. 
  The 
  dyke 
  is 
  here 
  about 
  100 
  

   feet 
  thick, 
  half 
  of 
  which 
  is 
  formed 
  by 
  the 
  central 
  portion, 
  consisting 
  of 
  a 
  

   whitish 
  rhyolite 
  with 
  a 
  fine 
  laminated 
  structure, 
  breaking 
  in 
  prismatic 
  

   blocks 
  ; 
  the 
  rest 
  on 
  both 
  sides, 
  where 
  in 
  contact 
  with 
  the 
  agglomerates, 
  has 
  

   cooled 
  more 
  rapidly, 
  and 
  has 
  assumed 
  the 
  character 
  of 
  an 
  obsidian. 
  This 
  

   obsidian 
  is 
  greenish 
  or 
  brownish-black, 
  very 
  brittle, 
  and 
  imperfect 
  crystals 
  

   of 
  sanidine 
  are 
  enclosed 
  in 
  it. 
  This 
  dyke 
  can 
  be 
  traced 
  for 
  a 
  considerable 
  

   distance 
  upwards. 
  Where 
  overflowing 
  and 
  covering 
  the 
  agglomerates 
  it 
  

   forms 
  the 
  highest 
  peak 
  on 
  the 
  western 
  side 
  of 
  Gebbie's 
  Pass, 
  well 
  visible 
  

   from 
  Lyttelton 
  Harbour. 
  The 
  rock 
  here 
  is 
  divided 
  into 
  small 
  pentagonal 
  

   columns, 
  with 
  a 
  vertical 
  arrangement 
  ; 
  lower 
  down 
  the 
  pass, 
  the 
  same 
  

   coulee 
  has 
  a 
  tabular 
  structure. 
  

  

  The 
  oldest 
  crater, 
  of 
  which 
  the 
  principal 
  boundaries 
  can 
  be 
  traced 
  at 
  the 
  

   present 
  time, 
  is 
  the 
  Lyttelton 
  Harbour 
  caldera, 
  having 
  a 
  general 
  diameter 
  

   of 
  about 
  two 
  miles, 
  the 
  centre 
  of 
  which 
  is 
  situated 
  a 
  little 
  to 
  the 
  south 
  of 
  

   Quail 
  Island. 
  The 
  general 
  structure 
  of 
  this 
  crater, 
  even 
  before 
  the 
  Christ- 
  

   church 
  and 
  Lyttelton 
  Eailway 
  tunnel 
  was 
  entirely 
  pierced 
  through, 
  could 
  

   easily 
  be 
  made 
  out 
  by 
  studying 
  the 
  numerous 
  sections 
  exposed 
  in 
  many 
  

   directions, 
  and 
  by 
  ascending 
  the 
  steep 
  escarpments 
  of 
  the 
  caldera 
  wall, 
  

   where 
  a 
  succession 
  of 
  streams 
  of 
  stony 
  or 
  scoriaceous 
  lava, 
  interstratified 
  

  

  a33 
  

  

  