﻿316 
  

  

  J. 
  E. 
  MARR 
  OX 
  THE 
  CAMBRIAN 
  AND 
  

  

  ferns-shales 
  seen 
  consist 
  of 
  thin 
  black 
  " 
  wafer 
  " 
  shales 
  crowded 
  with 
  

   Climacograptus 
  normalis, 
  and 
  interbedded 
  with 
  grits. 
  

  

  In 
  a 
  lane 
  near 
  Nitsjo, 
  the 
  red 
  beds 
  of 
  the 
  Trinncleus- 
  shales 
  are 
  

   succeeded 
  by 
  a 
  thin 
  bed 
  of 
  white 
  gritty 
  oolitic 
  limestone, 
  above 
  

   which 
  Tornqvist 
  has 
  seen 
  the 
  Lobiferns-shales 
  ; 
  bnt 
  these 
  are 
  no 
  

   longer 
  exposed. 
  This 
  limestone 
  here 
  represents 
  the 
  base 
  of 
  the 
  

   Silurian, 
  and 
  is, 
  as 
  will 
  be 
  described 
  hereafter, 
  similar 
  to 
  other 
  beds 
  

   occupying 
  the 
  same 
  position 
  in 
  other 
  areas 
  of 
  Sweden. 
  

  

  The 
  Lobiferus-beds 
  of 
  Dalecarlia 
  indicate 
  somewhat 
  shallower- 
  

   water 
  conditions 
  than 
  do 
  their 
  graptoliferous 
  equivalents 
  in 
  other 
  

   countries. 
  They 
  are 
  grey, 
  often 
  gritty 
  shales, 
  containing 
  Grapto- 
  

   lites, 
  sometimes 
  along 
  with 
  higher 
  organisms, 
  as 
  at 
  Kallholn. 
  

  

  The 
  Retiolites-shales 
  are 
  more 
  flaggy 
  than 
  the 
  Lobiferus-shales. 
  

   They 
  are 
  usually 
  light 
  grey, 
  sometimes 
  green 
  or 
  red, 
  and 
  have 
  

   interbedded 
  calcareous 
  bands 
  and 
  nodules. 
  They 
  are 
  well 
  seen 
  at 
  

   Stygforsen 
  near 
  Boda, 
  where 
  they 
  are 
  faulted 
  against 
  the 
  " 
  Slip- 
  

   sandsten." 
  

  

  Leptcena-Limestone. 
  — 
  This 
  is 
  the 
  most 
  puzzling 
  of 
  all 
  the 
  Dale- 
  

   carlian 
  formations. 
  It 
  consists 
  principally 
  of 
  a 
  coarsely 
  crystalline 
  

   white 
  limestone, 
  with 
  interbedded 
  shaly 
  partings. 
  Gritty 
  beds 
  

   occur 
  in 
  places, 
  as 
  near 
  Rattvik, 
  on 
  Lake 
  Siljan. 
  The 
  lower 
  part 
  

   is 
  formed 
  of 
  thin-bedded 
  shaly 
  green 
  limestones 
  as 
  seen 
  at 
  Arfvet 
  

   and 
  Boda. 
  The 
  fauna 
  would 
  at 
  first 
  sight 
  seem 
  to 
  indicate 
  a 
  

   position 
  below 
  the 
  Retiolites-beds, 
  and 
  even 
  below 
  the 
  Lobiferus-beds. 
  

   The 
  limestone 
  is 
  hardly 
  ever 
  seen 
  in 
  its 
  true 
  place, 
  occurring 
  usually 
  

   as 
  a 
  boss 
  in 
  the 
  middle 
  of 
  a 
  valley, 
  with 
  no 
  rocks 
  exposed 
  on 
  either 
  

   side. 
  In 
  many 
  cases 
  its 
  present 
  position 
  is 
  due 
  to 
  faulting, 
  and 
  

   perhaps 
  in 
  some 
  cases, 
  as 
  suggested 
  by 
  Dr. 
  Tornqvist, 
  to 
  transpor- 
  

   tation 
  by 
  ice 
  during 
  the 
  glacial 
  period. 
  A 
  summary 
  of 
  the 
  evidence 
  

   for 
  placing 
  it 
  above 
  the 
  Retiolites-beds 
  may 
  be 
  given 
  : 
  — 
  

  

  (i.) 
  It 
  cannot 
  be 
  below 
  the 
  Trinucleus-shales, 
  as 
  a 
  continuous 
  

   sequence 
  is 
  often 
  exposed 
  below 
  these 
  beds. 
  

  

  (ii.) 
  It 
  cannot 
  be 
  between 
  the 
  Trinucleus-shales 
  and 
  the 
  Lobi- 
  

   ferus-shales 
  ; 
  for 
  in 
  many 
  sections 
  these 
  beds 
  are 
  seen 
  very 
  near 
  

   together, 
  with 
  no 
  room 
  between 
  for 
  the 
  Leptsena-liinestone, 
  which 
  

   is 
  many 
  hundred 
  feet 
  in 
  thickness, 
  and 
  at 
  Nitsjo 
  the 
  interval 
  is 
  

   occupied 
  by 
  a 
  thin 
  band 
  of 
  limestone, 
  only 
  a 
  foot 
  or 
  two 
  in 
  

   thickness 
  ; 
  the 
  Lepta?na-limcstone 
  of 
  Boda 
  also 
  contains 
  fragments 
  

   of 
  other 
  rock, 
  including 
  a 
  green 
  grit, 
  probably 
  of 
  Precambrian 
  

   age, 
  and 
  also 
  of 
  shales 
  containing 
  Graptolites 
  characteristic 
  of 
  the 
  

   Lobiferus-beds. 
  These 
  fragments 
  are 
  often 
  of 
  great 
  size, 
  some 
  being 
  

   several 
  feet 
  in 
  diameter, 
  and 
  quite 
  angular; 
  and 
  they 
  may 
  have 
  been 
  

   brought 
  from 
  the 
  north 
  by 
  floating 
  ice. 
  

  

  (iii.) 
  The 
  Leptsena-limestone 
  cannot 
  occur 
  between 
  the 
  Lobiferus- 
  

   and 
  Retiolites-shales, 
  as 
  the 
  former 
  pass 
  gradually 
  into 
  the 
  latter, 
  as 
  

   seen 
  at 
  Kallholn. 
  If 
  the 
  fragments 
  of 
  Lobiferus-beds 
  included 
  in 
  

   the 
  LeptaBna-limestone 
  be 
  supposed 
  to 
  come 
  from 
  the 
  north, 
  this 
  

   will 
  account 
  for 
  the 
  absence 
  of 
  fragments 
  of 
  Retiolites-shales 
  in 
  the 
  

   same 
  beds; 
  for 
  these 
  were 
  not 
  deposited 
  further 
  north, 
  as 
  will 
  be 
  

   seen 
  in 
  the 
  sequel. 
  

  

  