﻿114 
  H. 
  T. 
  Hill 
  — 
  Reconnaissance 
  of 
  the 
  

  

  stones 
  and 
  eruptives 
  ; 
  the 
  keystone 
  or 
  central 
  Chickasaw 
  

   region, 
  consists 
  of 
  an 
  area 
  of 
  granite 
  and 
  Silurian 
  limestones. 
  

  

  1. 
  The 
  Eastern 
  or 
  Arkansas- 
  Choctaw 
  Division. 
  — 
  The 
  north- 
  

   ern 
  two-thirds 
  of 
  the 
  Choctaw 
  nation 
  and 
  the 
  northeastern 
  

   Chickasaw 
  country 
  are 
  a 
  direct 
  continuation 
  of 
  the 
  mountains 
  

   and 
  geologic 
  features 
  of 
  west-central 
  Arkansas. 
  This 
  region 
  

   consists 
  of 
  numerous 
  timber-covered 
  ridges 
  varying 
  in 
  altitude 
  

   from 
  2700 
  feet 
  along 
  the 
  Arkansas 
  line 
  to 
  1200 
  along 
  the 
  

   Missouri, 
  Kansas 
  and 
  Texas 
  railroad. 
  The 
  ridges 
  are 
  usually 
  

   elongated, 
  timbered, 
  devoid 
  of 
  sharp 
  peaks 
  and 
  owe 
  their 
  pres- 
  

   ent 
  form 
  to 
  the 
  unequal 
  erosion 
  of 
  the 
  exaggerated 
  structural 
  

   folds. 
  The 
  general 
  trend 
  of 
  these 
  mountains, 
  corresponding 
  

   with 
  the 
  strike 
  of 
  the 
  folds, 
  is 
  south 
  of 
  westward, 
  but 
  often, 
  as 
  

   seen 
  near 
  Stringtown 
  and 
  along 
  the 
  Kiamitia 
  River, 
  it 
  is 
  

   nearer 
  north 
  and 
  south. 
  The 
  ridges 
  consist 
  of 
  sandstones, 
  

   clays 
  and 
  shales 
  apparently 
  of 
  the 
  Carboniferous 
  period, 
  but 
  

   further 
  investigation 
  may 
  reveal 
  older 
  rocks. 
  The 
  rocks 
  occur 
  

   in 
  numerous 
  parallel, 
  overlapping 
  folds, 
  which 
  are 
  nearly 
  

   vertical 
  in 
  the 
  southern 
  and 
  central 
  portion 
  of 
  their 
  extent, 
  

   but 
  become 
  horizontal 
  along 
  their 
  northern 
  outline. 
  

  

  Z,ovrer 
  HelOerberg, 
  

  

  £ 
  Scale 
  ofrntles 
  

  

  Section 
  north 
  and 
  south 
  across 
  Red 
  Bird 
  Mts.. 
  showing- 
  relation 
  of 
  Mountain 
  folds 
  to 
  

   Cretaceous 
  Prairies. 
  

  

  The 
  Saint 
  Louis 
  and 
  San 
  Francisco 
  railroad, 
  from 
  Fort 
  

   Smith, 
  Arkansas, 
  to 
  Paris, 
  Texas, 
  passes 
  through 
  the 
  heart 
  of 
  

   the 
  region, 
  and 
  the 
  type 
  structure, 
  as 
  seen 
  along 
  this 
  route, 
  

   consists 
  of 
  vertical 
  eastward 
  folds 
  dislocated 
  by 
  another 
  and 
  

   later 
  movement, 
  as 
  seen 
  south 
  of 
  Tushka 
  Homa, 
  the 
  Choctaw 
  

   capital. 
  This 
  road 
  follows 
  for 
  miles 
  the 
  water 
  gap 
  of 
  the 
  

   Kiamitia 
  River, 
  which 
  apparently 
  flows 
  in 
  an 
  anticlinal 
  valley. 
  

   A 
  hundred 
  miles 
  west 
  of 
  this 
  railway, 
  the 
  Missouri, 
  Kansas 
  

   and 
  Texas 
  road 
  affords 
  another 
  parallel 
  north 
  and 
  south 
  section 
  

   of 
  the 
  mountain 
  system, 
  but 
  owing 
  to 
  the 
  gradual 
  cessation 
  of 
  

   timber 
  and 
  decreasing 
  altitude 
  entirely 
  different 
  scenic 
  effects 
  

   are 
  revealed. 
  The 
  latter 
  road 
  follows 
  the 
  valley 
  prairies 
  

   between 
  the 
  mountain 
  ridges, 
  which 
  here 
  have 
  the 
  contour 
  and 
  

   altitude 
  which, 
  in 
  Kentucky, 
  would 
  be 
  called 
  knobs. 
  The 
  

   railroad 
  follows 
  the 
  strike 
  of 
  the 
  structure 
  from 
  Atoka 
  to 
  

   Limestone 
  Gap. 
  The 
  differences 
  in 
  elevation 
  are 
  the 
  result 
  of 
  

   unequal 
  weathering 
  of 
  the 
  crumbling 
  shales 
  and 
  the 
  more 
  

   resisting 
  sandstones 
  and 
  limestones, 
  the 
  former 
  being 
  treeless 
  

   valleys 
  while 
  the 
  latter 
  persist 
  as 
  mountainous 
  ridges. 
  (Fig. 
  

   3.) 
  Timber 
  grows 
  upon 
  the 
  sandstone 
  outcrops 
  while 
  the 
  

  

  