﻿370 
  C. 
  J. 
  A. 
  MEYEK 
  ON 
  THE 
  CKETACEOTJS 
  EOCKS 
  OE 
  

  

  older 
  deposits. 
  The 
  Oolitic, 
  the 
  Liassic, 
  the 
  Triassic, 
  and 
  Old-Red- 
  

   Sandstone 
  strata 
  support 
  in 
  turn 
  the 
  overlying 
  Cretaceous 
  series. 
  

   In 
  passing 
  westward 
  these 
  Cretaceous 
  rocks 
  diminish 
  steadily, 
  yet 
  

   at 
  the 
  same 
  time 
  unequally, 
  in 
  thickness. 
  They 
  change 
  slightly, 
  

   also, 
  both 
  in 
  mineral 
  character 
  and 
  in 
  their 
  fossil 
  contents. 
  From 
  

   Lyme 
  Regis 
  westward 
  to 
  Axmouth, 
  and 
  from 
  Beer 
  Head 
  again 
  west- 
  

   wards 
  to 
  their 
  last 
  exposure 
  on 
  the 
  coast 
  at 
  Peak 
  Hill, 
  near 
  Sidmouth, 
  

   the 
  base 
  of 
  the 
  series 
  rises 
  gradually 
  higher 
  in 
  the 
  cliff-sections. 
  

  

  In 
  the 
  face 
  of 
  this 
  prevailing 
  rise 
  of 
  the 
  Cretaceous 
  series 
  to 
  the 
  

   westward, 
  the 
  Chalk-cliffs 
  of 
  Beer 
  Head, 
  the 
  most 
  westerly 
  chalk 
  

   promontory 
  in 
  England, 
  owe 
  their 
  preservation 
  in 
  great 
  measure 
  to 
  

   a 
  local 
  synclinal 
  or 
  trough-like 
  arrangement 
  of 
  the 
  strata. 
  

  

  Many 
  writers 
  on 
  the 
  geology 
  of 
  Devonshire 
  have 
  attributed 
  the 
  

   present 
  trough-like 
  arrangement 
  of 
  these 
  strata 
  to 
  subsidence 
  since 
  

   their 
  original 
  deposition. 
  It 
  is 
  not 
  clear, 
  however, 
  that 
  this 
  view 
  is 
  

   correct 
  ; 
  and 
  it 
  may, 
  perhaps, 
  be 
  worth 
  considering 
  presently 
  whether 
  

   this 
  seeming 
  subsidence 
  is 
  not 
  due 
  in 
  part 
  to 
  an 
  original 
  inequality 
  of 
  

   the 
  ocean-bed. 
  For 
  the 
  moment 
  I 
  must 
  pass 
  on 
  to 
  other 
  matters. 
  

  

  I. 
  Cretaceous 
  Rocks 
  represented 
  in 
  tlie 
  Cliff-Sections 
  of 
  South 
  

   Devonshire. 
  

  

  The 
  Cretaceous 
  rocks 
  of 
  the 
  Beer-Head 
  district 
  include 
  the 
  fol- 
  

   lowing 
  principal 
  subdivisions 
  : 
  — 
  

  

  Upper 
  Chalk 
  (in 
  part) 
  ? 
  

   Middle 
  Chalk. 
  

   Lower 
  Chalk. 
  

   Chalk 
  Marl. 
  

   Chloritic 
  Marl. 
  

   Upper 
  Grcensand. 
  

   Gault. 
  

   (?) 
  

  

  These 
  broader 
  and 
  generally 
  recognized 
  divisions 
  are 
  split 
  up 
  

   naturally 
  into 
  many 
  minor 
  beds, 
  either 
  by 
  variation 
  in 
  mineral 
  

   composition 
  or 
  by 
  the 
  prevalence 
  of 
  a 
  special 
  fauna. 
  

  

  In 
  describing 
  these 
  minor 
  beds, 
  or 
  groups 
  of 
  strata, 
  it 
  may 
  be 
  most 
  

   convenient 
  to 
  take 
  them 
  in 
  their 
  natural 
  or 
  ascending 
  order, 
  and 
  for 
  

   facility 
  of 
  reference 
  to 
  number 
  them 
  throughout 
  consecutively. 
  

  

  Description 
  of 
  the 
  minor 
  Subdivisions 
  of 
  the 
  Cretaceous 
  Strata 
  as 
  

   seen 
  in 
  the 
  Beer-Head* 
  and 
  adjacent 
  Sections 
  (fig. 
  1). 
  

  

  Bed 
  1. 
  — 
  Greenish 
  sandy 
  argillaceous 
  strata. 
  Including 
  often, 
  

   near 
  its 
  base, 
  a 
  grit-bed 
  of 
  minute 
  subangular 
  pebbles, 
  or 
  frag- 
  

   ments 
  of 
  the 
  underlying 
  rocks. 
  

  

  Thickness 
  variable, 
  usually 
  a 
  few 
  feet 
  only 
  : 
  3 
  ft. 
  at 
  White 
  

   Cliff, 
  3| 
  ft. 
  at 
  Dunscombe, 
  2| 
  feet 
  at 
  Salcombe 
  Hill. 
  

  

  Prevailing 
  fossil 
  — 
  Exogyra 
  conica 
  (small 
  var.). 
  

  

  * 
  The 
  sections 
  here 
  referred 
  to 
  as 
  adjacent 
  sections 
  are 
  : 
  — 
  those 
  of 
  White 
  Cliff 
  

   and 
  Beer 
  ; 
  the 
  Southdown 
  Undercliff, 
  or 
  landslip 
  of 
  1789 
  ; 
  the 
  cliffs 
  at 
  Brans- 
  

   combe 
  Mouth, 
  Weston 
  Mouth, 
  Dunscombe, 
  Salcombe^ 
  and 
  Sidmouth. 
  

  

  