﻿348 
  W. 
  G. 
  Foye— 
  Geology 
  of 
  the 
  Lau 
  Islands. 
  

  

  cavities 
  are 
  thus 
  formed 
  and 
  the 
  collapse 
  of 
  their 
  roofs 
  gradu- 
  

   ally 
  develops 
  the 
  ramifying 
  bays. 
  The 
  writer 
  does 
  not 
  agree 
  

   with 
  Davis 
  that 
  these 
  bays 
  are 
  necessarily 
  evidence 
  of 
  subsi- 
  

   dence 
  in 
  sub-recent 
  times. 
  

  

  2. 
  Lakemba 
  (fig. 
  2). 
  

  

  The 
  island 
  of 
  Lakemba 
  was 
  probably 
  never 
  completely 
  

   covered 
  with 
  limestone. 
  The 
  volcanic 
  surface, 
  reaching 
  a 
  

   maximum 
  elevation 
  of 
  nearly 
  800 
  feet, 
  is 
  composed 
  of 
  well- 
  

   rounded, 
  mature 
  forms. 
  The 
  rocks 
  are 
  deeply 
  lateritized 
  and 
  

   support 
  a 
  scant 
  vegetation. 
  

  

  Along 
  the 
  boundary 
  of 
  the 
  volcanic 
  area 
  are 
  isolated 
  rem- 
  

   nants 
  of 
  elevated 
  limestone 
  which 
  once 
  encircled 
  the 
  island. 
  

   These 
  remnants 
  unconformably 
  overlie 
  the 
  volcanic 
  rocks 
  and 
  

   rise 
  to 
  a 
  maximum 
  elevation 
  of 
  320 
  feet. 
  Near, 
  the 
  northern 
  

   side 
  of 
  the 
  island 
  spur-ridges 
  100 
  feet 
  high 
  and 
  their 
  interven- 
  

   ing 
  valleys 
  are 
  covered 
  with 
  a 
  mantle 
  of 
  shell 
  and 
  coral 
  rubble 
  

   containing 
  volcanic 
  pebbles. 
  Traced 
  west 
  and 
  south, 
  this 
  basal 
  

   deposit 
  is 
  transitional 
  upward 
  into 
  coral-reef 
  limestone. 
  

  

  The 
  remnants 
  of 
  limestone 
  decrease 
  in 
  altitude 
  along 
  the 
  

   coast 
  towards 
  the 
  eastern 
  side 
  of 
  the 
  island. 
  They 
  reach 
  a 
  

   maximum 
  elevation, 
  as 
  noted 
  above, 
  of 
  320 
  feet 
  at 
  its 
  north- 
  

   western 
  side 
  but 
  do 
  not 
  occur 
  on 
  the 
  side 
  hills 
  of 
  the 
  eastern 
  

   half. 
  

  

  These 
  facts 
  show 
  that 
  the 
  island, 
  bearing 
  an 
  unknown 
  num- 
  

   ber 
  of 
  andesitic 
  cones, 
  underwent 
  nature 
  erosion 
  and 
  subsided. 
  

   The 
  mature 
  topography 
  was 
  not 
  entirely 
  submerged 
  since 
  400 
  

   feet 
  of 
  the 
  island 
  still 
  remained 
  above 
  sea-level. 
  The 
  sunken 
  

   portion 
  was 
  overlain 
  by 
  320 
  feet, 
  or 
  more, 
  of 
  coraliferous 
  lime- 
  

   stone 
  and 
  was 
  later 
  uplifted. 
  

  

  The 
  disappearance 
  of 
  the 
  limestone 
  from 
  the 
  eastern 
  side 
  of 
  

   the 
  island 
  may 
  be 
  explained 
  in 
  two 
  ways. 
  It 
  may 
  be 
  due 
  to 
  

   more 
  rapid 
  solution 
  on 
  the 
  rain 
  side 
  of 
  the 
  island, 
  or 
  it 
  may 
  

   be 
  due 
  to 
  tilting 
  during 
  uplift. 
  If 
  erosion 
  were 
  the 
  cause 
  it 
  

   would 
  seem 
  that 
  the 
  rainy 
  side 
  of 
  the 
  island 
  should 
  show 
  a 
  

   more 
  mature 
  topography 
  than 
  the 
  dry 
  side. 
  It 
  is 
  significant 
  

   that 
  the 
  topographic 
  forms 
  on 
  the 
  western 
  side 
  show 
  greater 
  

   erosion 
  than 
  on 
  the 
  east. 
  This 
  fact, 
  with 
  others, 
  leads 
  the 
  

   writer 
  to 
  believe 
  that 
  the 
  island 
  has 
  been 
  tilted 
  toward 
  the 
  east. 
  

  

  The 
  reef 
  on 
  the 
  western 
  side 
  of 
  Lakemba 
  is 
  narrow 
  and 
  

   fringing 
  but 
  sweeps 
  far 
  out 
  and 
  includes 
  a 
  lagoon 
  8 
  or 
  10 
  miles 
  

   wide 
  on 
  the 
  northeastern 
  side. 
  The 
  mouths 
  of 
  the 
  rivers 
  on 
  

   the 
  eastern 
  side 
  are 
  deeply 
  embayed. 
  The 
  width 
  of 
  the 
  west- 
  

   ern 
  reef 
  would 
  suggest 
  that 
  it 
  has 
  been 
  established 
  in 
  sub- 
  

   recent 
  times 
  b} 
  T 
  uplift, 
  whereas 
  the 
  eastern 
  reef 
  has 
  either 
  been 
  

   long 
  established 
  or 
  recently 
  submerged. 
  The 
  recent 
  uplift 
  of 
  

   the 
  western 
  coast 
  would 
  favor 
  a 
  tilting 
  to 
  the 
  east. 
  

  

  