﻿118 
  GE0KGE 
  MAW'S 
  NOTES 
  ON 
  A 
  JOTJRNEY 
  

  

  the 
  section. 
  Of 
  eruptive 
  rocks 
  there 
  are 
  no 
  traces 
  in 
  any 
  part 
  of 
  the 
  

   district 
  between 
  Algiers 
  and 
  L'Aghouat. 
  The 
  oldest 
  rock 
  is 
  the 
  boss 
  

   of 
  micaceous 
  schists 
  and 
  gneiss 
  at 
  the 
  back 
  of 
  Algiers, 
  striking 
  nearly- 
  

   north 
  and 
  south 
  and 
  dipping 
  away 
  east 
  and 
  west 
  from 
  a 
  low 
  anti- 
  

   clinal, 
  the 
  crest 
  of 
  which 
  occurs 
  near 
  the 
  Fort 
  de 
  l'Empereur 
  at 
  the 
  

   summit 
  of 
  the 
  hill. 
  

  

  Socks 
  of 
  the 
  Lower 
  Atlas 
  and 
  Anticlinal 
  north 
  of 
  Berouaguia. 
  — 
  The 
  

   pass 
  through 
  the 
  gorge 
  of 
  La 
  Chiffa 
  exposes 
  hard 
  slaty 
  rocks, 
  dipping 
  

   south 
  at 
  a 
  high 
  angle 
  and 
  somewhat 
  cleaved, 
  which 
  appear 
  repeated 
  

   as 
  an 
  anticlinal 
  on 
  the 
  south 
  side 
  of 
  the 
  higher 
  part 
  of 
  the 
  Tell 
  

   Plateau. 
  They 
  contain 
  no 
  fossils 
  ; 
  and 
  but 
  for 
  their 
  being 
  confor- 
  

   mable 
  to 
  the 
  overlying 
  Neocomian 
  beds, 
  I 
  should, 
  judging 
  from 
  their 
  

   physical 
  character, 
  place 
  them 
  on 
  a 
  much 
  lower 
  horizon. 
  There 
  is 
  

   no 
  satisfactory 
  evidence 
  as 
  to 
  their 
  age. 
  They 
  strike 
  N.N.E. 
  by 
  

   W.S.W., 
  and 
  closely 
  resemble 
  in 
  mineral 
  character 
  the 
  nearly 
  vertical 
  

   slaty 
  shales 
  on 
  the 
  northern 
  flanks 
  of 
  the 
  Great 
  Atlas 
  south 
  of 
  the 
  

   city 
  of 
  Marocco. 
  

  

  Sandstones 
  of 
  Guelt-el-Stel 
  and 
  Sidi 
  Makhelouf. 
  — 
  In 
  the 
  denuded 
  

   plain 
  separating 
  the 
  Tell 
  from 
  the 
  Hauts 
  Plateaux, 
  and 
  again 
  on 
  the 
  

   south 
  side 
  of 
  the 
  Hauts 
  Plateaux, 
  red 
  and 
  yellow 
  sandstones 
  are 
  

   thrown 
  up 
  as 
  anticlinals, 
  between 
  which 
  the 
  overlying 
  beds 
  of 
  the 
  

   Hauts 
  Plateaux 
  form 
  an 
  elevated 
  synclinal. 
  There 
  is 
  no 
  palseontolo- 
  

   gical 
  evidence 
  as 
  to 
  their 
  age 
  ; 
  but 
  they 
  resemble 
  the 
  Bunter 
  in 
  mineral 
  

   character, 
  and 
  are 
  overlain 
  by 
  red 
  marls 
  resembling 
  the 
  Keuper. 
  A 
  

   similar 
  succession 
  of 
  beds 
  of 
  Triassic 
  age 
  occurs 
  in 
  the 
  south 
  of 
  

   Portugal 
  ; 
  and 
  I 
  am 
  informed 
  by 
  Mr. 
  Tristram 
  that 
  red 
  sandstone, 
  

   supposed 
  to 
  be 
  of 
  Triassic 
  age, 
  comes 
  to 
  the 
  surface 
  at 
  Warigla 
  in 
  the 
  

   M'Zab 
  country, 
  S.W. 
  of 
  L'Aghouat, 
  probably 
  as 
  a 
  third 
  anticlinal. 
  

  

  Saliferous 
  Marls 
  of 
  the 
  Rochers 
  de 
  Sel. 
  — 
  The 
  northern 
  escarpment 
  

   of 
  the 
  Hauts 
  Plateaux 
  is 
  the 
  only 
  point 
  in 
  the 
  section 
  where 
  the 
  

   saliferous 
  marls 
  are 
  clearly 
  exposed. 
  I 
  must 
  take 
  exception 
  to 
  the 
  

   view 
  expressed 
  by 
  Mr. 
  Tristram, 
  in 
  his 
  ' 
  Great 
  Sahara,' 
  that 
  they 
  

   are 
  " 
  an 
  eruption 
  of 
  argillaceous 
  calcareous 
  mud 
  and 
  rock-salt 
  up- 
  

   heaved 
  across 
  the 
  Secondary 
  and 
  Tertiary 
  deposits." 
  Although 
  

   they 
  appear 
  isolated, 
  they 
  occupy 
  a 
  well-marked 
  horizon 
  in 
  the 
  

   Mesozoic 
  beds 
  at 
  the 
  base 
  of 
  the 
  Hauts 
  Plateaux 
  ; 
  and 
  though 
  absent 
  

   in 
  similar 
  positions 
  at 
  other 
  parts 
  of 
  the 
  section, 
  they 
  are 
  clearly 
  

   interstratified 
  between 
  the 
  sandstones 
  below 
  and 
  the 
  red 
  marls, 
  grey 
  

   marls, 
  and 
  rocky 
  courses 
  above. 
  In 
  mineral 
  character 
  they 
  resemble 
  

   the 
  salt 
  deposit 
  at 
  Bex, 
  in 
  Switzerland. 
  Crystals 
  of 
  salt 
  and 
  gypsum 
  

   are 
  intimately 
  mixed 
  up 
  with 
  the 
  grey 
  marls. 
  Ten 
  or 
  fifteen 
  miles 
  

   north 
  of 
  the 
  Rochers 
  de 
  Sel, 
  the 
  presence 
  of 
  these 
  marls 
  is 
  indicated 
  by 
  

   the 
  two 
  great 
  salt 
  lakes, 
  or 
  Zahrez 
  ; 
  but 
  south 
  of 
  the 
  Hauts 
  Plateaux, 
  

   although 
  their 
  horizon 
  can 
  be 
  identified, 
  I 
  observed 
  no 
  salt 
  deposits 
  ; 
  

   and 
  if 
  they 
  occur 
  in 
  the 
  north 
  Sahara 
  plain, 
  their 
  presence 
  is 
  obscured 
  

   by 
  the 
  surface-deposit 
  of 
  grey 
  loam 
  and 
  calcareous 
  crust. 
  

  

  The 
  patchy 
  occurrence, 
  so 
  to 
  speak, 
  of 
  the 
  salt 
  corresponds 
  with 
  

   the 
  isolated 
  distribution 
  of 
  salt 
  rock 
  in 
  the 
  Keuper 
  of 
  Worcestershire 
  

   and 
  Cheshire. 
  

  

  Bed 
  and 
  Green 
  Marls. 
  — 
  Overlying 
  the 
  red 
  sandstones, 
  a 
  thin 
  series 
  

  

  