﻿22 
  0. 
  Holtedahl 
  — 
  Paleo 
  geography 
  and 
  

  

  crust 
  movements 
  met 
  with 
  in 
  the 
  geosynclinal 
  belts. 
  

   Willis's 
  theory 
  of 
  the 
  "sub-oceanic 
  spread/' 
  applied 
  to 
  

   the 
  Appalachian 
  zone 
  of 
  deformation 
  and 
  illustrated 
  by 
  

   Ulrich 
  in 
  his 
  "Revision," 
  p. 
  439, 
  has 
  as 
  a 
  requirement 
  

   a 
  bordering 
  deep 
  oceanic 
  basin. 
  The 
  planes 
  of 
  fracture 
  

   and 
  thrust 
  must, 
  as 
  a 
  consequence 
  of 
  the 
  pressure 
  from 
  

   a 
  deep-seated 
  mass, 
  be 
  directed 
  obliquely 
  upward. 
  Com- 
  

   paring 
  with 
  this 
  view 
  the 
  well-known 
  geologic 
  structure 
  

   of 
  northwestern 
  Scotland, 
  where 
  the 
  thrust 
  planes 
  are 
  

   directed 
  obliquely 
  downward, 
  toward 
  the 
  southeast, 
  we 
  

   meet 
  here 
  exactly 
  the 
  opposite 
  condition; 
  hence 
  a 
  pres- 
  

   sure 
  from 
  the 
  side 
  of 
  the 
  present 
  ocean 
  (we 
  have 
  then 
  to 
  

   assume 
  what 
  seems 
  very 
  probable, 
  an 
  underthrust 
  and 
  

   not 
  an 
  overthrust 
  movement) 
  can 
  in 
  this 
  case 
  hardly 
  be 
  

   thought 
  to 
  have 
  come 
  from 
  the 
  deep. 
  

  

  It 
  is 
  in 
  the 
  nature 
  of 
  the 
  region 
  under 
  consideration 
  

   that 
  the 
  movements 
  of 
  the 
  shore-line 
  are 
  of 
  quite 
  another 
  

   character 
  than 
  those 
  of 
  the 
  North 
  American 
  continent, 
  a 
  

   part 
  of 
  the 
  crust 
  that, 
  with 
  the 
  exception 
  of 
  the 
  border- 
  

   ing 
  belts, 
  has 
  behaved 
  like 
  a 
  rather 
  compact 
  mass, 
  the 
  

   surface 
  of 
  which 
  was 
  subjected 
  only 
  to 
  warpings 
  of 
  no 
  

   very 
  great 
  importance. 
  The 
  continent 
  has 
  thus 
  behaved 
  

   in 
  a 
  certain 
  passive 
  way, 
  the 
  moving 
  of 
  the 
  shore-line, 
  as 
  

   assumed 
  by 
  American 
  paleogeographers, 
  being 
  caused 
  

   by 
  movements 
  chiefly 
  outside 
  the 
  present 
  continent, 
  espe- 
  

   cially 
  by 
  the 
  more 
  or 
  less 
  periodic 
  vertical 
  movements 
  

   of 
  the 
  bottom 
  of 
  the 
  surrounding 
  ocean 
  basins. 
  In 
  the 
  

   region 
  here 
  treated, 
  the 
  movement 
  of 
  the 
  shore-line 
  is 
  

   for 
  large 
  areas 
  chiefly 
  due 
  to 
  an 
  active 
  movement 
  of 
  the 
  

   crust 
  in 
  these 
  areas 
  themselves. 
  It 
  is 
  the 
  uplift 
  in 
  the 
  

   region 
  itself 
  that 
  causes 
  the 
  emergence, 
  not 
  a 
  movement 
  

   in 
  a 
  far-away 
  ocean 
  basin. 
  The 
  effect 
  of 
  these 
  latter 
  

   movements 
  is 
  generally 
  only 
  of 
  secondary 
  importance. 
  

   From 
  the 
  fact, 
  then, 
  that 
  the 
  crustal 
  movements 
  to 
  a 
  

   great 
  degree 
  occur 
  at 
  different 
  times 
  in 
  different 
  places, 
  

   it 
  will 
  be 
  understood 
  how 
  difficult 
  or 
  rather 
  impossible 
  it 
  

   will 
  be 
  to 
  apply 
  in 
  a 
  satisfactory 
  manner 
  to 
  northwestern 
  

   Europe 
  and 
  the 
  Arctic 
  regions 
  farther 
  to 
  the 
  north 
  the 
  

   method 
  natural 
  for 
  North 
  America 
  of 
  delimiting 
  the 
  

   geological 
  epochs 
  and 
  periods 
  according 
  to 
  the 
  history 
  

   of 
  transgressions 
  and 
  regressions. 
  A 
  crust 
  movement 
  

   that 
  may 
  in 
  one 
  district 
  cause 
  transgression, 
  in 
  another 
  

   causes 
  regression, 
  while 
  in 
  a 
  third, 
  conditions 
  are 
  prac- 
  

   tically 
  unaltered. 
  Even 
  for 
  the 
  relatively 
  stable 
  areas 
  

  

  