﻿Geological 
  and 
  Physical 
  Development 
  of 
  Dominica. 
  553 
  

  

  the 
  early 
  Pleistocene 
  epoch 
  thus 
  appears 
  to 
  have 
  stood 
  for 
  a 
  limited 
  

   time 
  at 
  an 
  altitude 
  of 
  6000 
  or 
  7000 
  feet, 
  as 
  shown 
  within 
  the 
  

   limits 
  of 
  the 
  Antillean 
  mass 
  (and 
  still 
  higher 
  from 
  evidence 
  beyond). 
  

   There 
  are 
  no 
  coastal 
  plains, 
  strictly 
  speaking 
  ; 
  only 
  to 
  a 
  very 
  limited 
  

   extent 
  are 
  the 
  islands 
  surrounded 
  by 
  shelves 
  submerged 
  to 
  a 
  depth 
  

   of 
  less 
  than 
  200 
  feet. 
  But 
  the 
  Grenadine 
  banks 
  are 
  extensive. 
  

   One 
  or 
  two 
  outlying 
  remnants 
  of 
  the 
  Antillean 
  plateau 
  occur 
  south- 
  

   east 
  of 
  Dominica, 
  and 
  another 
  about 
  60 
  miles 
  east 
  of 
  Martinique, 
  

   all 
  of 
  which 
  may 
  be 
  fragments 
  of 
  the 
  old 
  coastal 
  plains. 
  

  

  All 
  the 
  islands 
  are 
  underlaid 
  by 
  old 
  Tertiary 
  or 
  pre-Tertiary 
  

   igneous 
  rocks, 
  as 
  in 
  Guadeloupe. 
  Such, 
  where 
  exposed, 
  are 
  found 
  

   to 
  be 
  very 
  much 
  decayed. 
  Elsewhere, 
  the)'' 
  are 
  covered 
  by 
  tuffs 
  

   with 
  only 
  angular 
  breccia. 
  Upon 
  such 
  surfaces, 
  denuded, 
  rest 
  other 
  

   tuffs 
  derived 
  from 
  older 
  deposits, 
  containing 
  waterworn 
  pebbles, 
  in 
  

   lines 
  of 
  bedding. 
  These 
  last 
  may 
  be 
  the 
  equivalent 
  of 
  the 
  Tertiary 
  

   tuffs 
  and 
  limestones 
  of 
  Guadeloupe. 
  Upon 
  their 
  eroded 
  surface 
  

   rests 
  a 
  gravel-formation, 
  which 
  itself 
  has 
  largely 
  been 
  washed 
  away. 
  

   In 
  the 
  hollows 
  of 
  its 
  surface 
  is 
  found 
  another 
  formation 
  composed 
  of 
  

   coral-limestone, 
  containing 
  a 
  fauna 
  which 
  still 
  survives, 
  with 
  one 
  or 
  

   two 
  possibly 
  extinct 
  forms. 
  The 
  deposit 
  occupies 
  a 
  position 
  similar 
  

   to 
  one 
  in 
  Guadeloupe 
  and 
  another 
  in 
  St. 
  Kitts. 
  Its 
  surface 
  is 
  also 
  

   greatly 
  eroded, 
  and 
  then 
  covered 
  with 
  another 
  stratified 
  sand-and- 
  

   gravel 
  accumulation. 
  The 
  surface 
  of 
  the 
  slopes 
  is 
  often 
  covered 
  by 
  

   a 
  loam, 
  which 
  is, 
  in 
  part 
  at 
  least, 
  a 
  land-formation. 
  The 
  Pleistocene 
  

   Period 
  is 
  thus 
  seen 
  to 
  have 
  been 
  one 
  of 
  changing 
  physical 
  conditions. 
  

   The 
  older 
  Tertiarj^ 
  history 
  must 
  be 
  inferred 
  from 
  that 
  of 
  the 
  

   neighbouring 
  islands. 
  

  

  Lavas 
  may 
  be 
  seen 
  underlying 
  the 
  gravels, 
  and 
  accordingly 
  we 
  find 
  

   that 
  the 
  volcanic 
  activity 
  was 
  renewed, 
  after 
  a 
  very 
  long 
  Tertiary 
  

   quiescence, 
  in 
  the 
  Pleistocene 
  Period. 
  

  

  The 
  plains 
  underlaid 
  by 
  the 
  beds 
  of 
  old 
  tuffs 
  have 
  been 
  so 
  raised 
  

   up 
  as 
  to 
  give 
  rise 
  to 
  sloping 
  terraces 
  dipping 
  outward 
  from 
  the 
  late 
  

   volcanic 
  centres, 
  showing 
  that 
  their 
  elevation 
  has 
  been 
  due 
  to 
  local 
  

   uplifts, 
  and 
  not 
  to 
  regional 
  movements, 
  and 
  also 
  that 
  to 
  the 
  igneous 
  

   centres 
  alone 
  are 
  confiued 
  the 
  volcanic 
  uplifts, 
  which 
  do 
  not 
  extend 
  

   to 
  such 
  remnants 
  of 
  coastal 
  plains 
  as 
  are 
  found 
  in 
  the 
  Antillean 
  

   region. 
  The 
  recent 
  terraces, 
  which 
  are 
  not 
  deformed, 
  are 
  small, 
  

   and 
  perhaps 
  do 
  not 
  rise 
  to 
  more 
  than 
  70 
  feet 
  above 
  the 
  sea. 
  

   Youthful 
  canons 
  are 
  being 
  formed 
  near 
  the 
  mouths 
  of 
  the 
  streams, 
  

   showing 
  the 
  recent 
  re-elevation 
  of 
  the 
  land. 
  

  

  3. 
  4 
  On 
  the 
  Geological 
  and 
  Physical 
  Development 
  of 
  Barbados, 
  

   with 
  Notes 
  on 
  Trinidad.' 
  Bv 
  Prof. 
  Joseph 
  William 
  Winthrop 
  

   Spencer, 
  Ph.D., 
  M.A., 
  F.G.S. 
  

  

  Barbados, 
  over 
  100 
  miles 
  east 
  of 
  the 
  main 
  chain 
  of 
  islands, 
  is 
  

   a 
  remnant 
  of 
  the 
  dismembered 
  and 
  sunken 
  Antillean 
  plateau, 
  with 
  

   the 
  embay 
  ment 
  in 
  it, 
  west 
  of 
  the 
  island, 
  reaching 
  to 
  a 
  depth 
  of 
  over 
  

   7000 
  feet. 
  But 
  the 
  drowned 
  Barbados 
  ridge 
  extends 
  far, 
  both 
  to 
  

  

  