﻿70-4 
  Geological 
  Society. 
  

  

  surface 
  subsides 
  until 
  the 
  underground 
  stream 
  is 
  revealed. 
  Solu- 
  

   tion 
  then 
  constantly 
  widens 
  the 
  stream-banks 
  into 
  bowls 
  of 
  soakage, 
  

   and 
  leaves 
  insoluble 
  material 
  to 
  build 
  up 
  a 
  broad, 
  level 
  valley-floor, 
  

   which 
  rises 
  gradually 
  above 
  and 
  obscures 
  the 
  dry 
  valley 
  outlet- 
  

   streams, 
  these 
  then 
  forming 
  marshes. 
  It 
  does 
  not 
  appear 
  possible 
  

   to 
  reconstruct 
  any 
  local 
  conditions 
  that 
  could 
  have 
  produced 
  these 
  

   valleys 
  by 
  mechanical 
  erosion, 
  and 
  it 
  is 
  suggested 
  that 
  they 
  are 
  

   formed 
  by 
  underground 
  solution, 
  and 
  are 
  therefore 
  called 
  joint- 
  

   valleys 
  or 
  solution-valleys. 
  Prestwich 
  (Quart. 
  Journ. 
  Geol. 
  

   Soc. 
  vol. 
  xxviii, 
  1872, 
  p. 
  lxvii) 
  estimates 
  that 
  140 
  tons 
  of 
  carbonate 
  

   of 
  lime 
  are 
  annually 
  removed 
  from 
  every 
  square 
  mile 
  of 
  the 
  

   limestone-area 
  drained 
  by 
  the 
  Thames. 
  This 
  would 
  give 
  an 
  annual 
  

   amount 
  removed 
  by 
  solution 
  from 
  the 
  small 
  Glyme 
  area 
  of 
  over 
  

   10,000 
  tons. 
  

  

  2. 
  'On 
  the 
  Stratigraphy 
  and 
  Structure 
  of 
  the 
  Tarnthal 
  Mass 
  

   (Tyrol).' 
  By 
  Alfred 
  Prentice 
  Young, 
  Ph.D., 
  F.G.S. 
  With 
  a 
  < 
  Note 
  

   on 
  two 
  Cephalopods 
  collected 
  on 
  the 
  Tarnthal 
  Kopfe 
  (Tyrol).' 
  

   By 
  George 
  C. 
  Crick, 
  Assoc.RS.H., 
  F.G.S. 
  

  

  The 
  immediate 
  occasion 
  for 
  this 
  paper 
  is 
  the 
  discovery 
  of 
  fossils 
  

   which 
  appear 
  to 
  throw 
  new 
  light 
  on 
  the 
  relations 
  of 
  the 
  rocks 
  of 
  

   this 
  mountain. 
  The 
  rock-series 
  may 
  be 
  divided 
  into 
  three 
  parts 
  : 
  — 
  

   (a) 
  The 
  lowest 
  portion 
  consists 
  of 
  dolomite, 
  and 
  the 
  Lias 
  is 
  in 
  

   normal 
  position, 
  the 
  upper 
  beds 
  being 
  the 
  youngest; 
  this 
  portion 
  is 
  

   scarcely 
  disturbed. 
  (6) 
  A 
  middle 
  section, 
  consisting 
  of 
  calcareous 
  

   schists, 
  with 
  a 
  band 
  of 
  massive 
  dolomite 
  and 
  dolomite-breccia, 
  

   shows 
  marks 
  of 
  violent 
  disturbance 
  and 
  crushing, 
  (c) 
  The 
  upper- 
  

   most 
  part, 
  a 
  mass 
  of 
  more 
  or 
  less 
  altered 
  quartzite-schists, 
  calcareous 
  

   schists, 
  and 
  serpentine, 
  retains 
  most 
  of 
  its 
  original 
  character 
  and 
  

   form, 
  having 
  undergone 
  little 
  mechanical 
  distortion 
  since 
  it 
  left 
  its 
  

   * 
  root.' 
  The 
  succession 
  is 
  summarized 
  as 
  follows 
  : 
  — 
  

  

  f 
  Serpentine. 
  

   Ophicalcite. 
  

   v 
  Tarnthal 
  quartzites, 
  etc. 
  

   {Calcareous 
  schists 
  with 
  green 
  bands. 
  

   Dolomite-breccias. 
  

   Calcareous 
  schists. 
  

   , 
  f 
  Liassic 
  limestone. 
  

   ' 
  [ 
  ' 
  Principal 
  dolomite 
  ' 
  (Rhaetic). 
  

  

  The 
  explanation 
  of 
  the 
  structure 
  now 
  suggested 
  is 
  as 
  follows: 
  — 
  

   The 
  line 
  between 
  1 
  and 
  2 
  marks 
  approximately 
  the 
  lower 
  loop 
  of 
  

   a 
  big 
  fold, 
  the 
  dolomite-breccia 
  being 
  a 
  repetition 
  in 
  an 
  attenuated 
  

   form 
  of 
  the 
  - 
  principal 
  dolomite 
  ' 
  below. 
  The 
  interpretation 
  of 
  the 
  

   relations 
  of 
  2 
  and 
  3 
  is 
  not 
  so 
  clear. 
  Either 
  the 
  whole 
  series 
  2 
  and 
  3 
  

   is 
  in 
  inverted 
  sequence, 
  or 
  else 
  the 
  dolomite-breccia 
  represents 
  the 
  

   whole 
  of 
  the 
  'principal 
  dolomite' 
  in 
  a 
  flattened 
  fold 
  (nappe 
  of 
  

   Termier), 
  the 
  serpentine 
  and 
  quartzite 
  having 
  been 
  brought 
  into 
  

   their 
  . 
  present 
  position 
  by 
  a 
  long 
  overthrust, 
  representing 
  the 
  

   traineau 
  ecraseur 
  of 
  the 
  French 
  geologists. 
  The 
  question 
  

   whether 
  the 
  lower 
  dolomite 
  and 
  the 
  Lias 
  are 
  in 
  situ 
  or 
  not 
  is 
  left 
  

   undecided. 
  A 
  petrographical 
  note 
  is 
  furnished 
  on 
  the 
  amphibolite 
  

   of 
  Gufidann. 
  

  

  