﻿122 
  B. 
  T. 
  Hill 
  — 
  Reconnaissance 
  of 
  the 
  

  

  terranes, 
  especially 
  in 
  the 
  Red 
  Bird 
  Mountains, 
  which 
  may 
  he 
  

   Cambrian. 
  

  

  Continuing 
  southward 
  along 
  our 
  section 
  the 
  mountains 
  cease 
  

   coincident 
  with 
  the 
  limestones, 
  and 
  after 
  a 
  mile 
  of 
  black 
  shales 
  

   (No. 
  7) 
  the 
  well-defined 
  Carboniferous 
  sands 
  and 
  shales 
  begin 
  

   near 
  Berwyn 
  and 
  continue 
  for 
  twenty-nine 
  miles 
  along 
  the 
  

   railroad 
  to 
  the 
  vicinity 
  of 
  Overbrook. 
  These 
  all 
  occur 
  in 
  

   vertical 
  folds, 
  apparently 
  coincident 
  with 
  or 
  at 
  least 
  a 
  part 
  of 
  

   the 
  same 
  system 
  to 
  which 
  the 
  Silurian 
  limestones 
  belong, 
  but 
  

   which, 
  owing 
  to 
  their 
  disintegrating 
  character, 
  have 
  been 
  

   leveled 
  down 
  to 
  a 
  low 
  undulating 
  plain. 
  Ten 
  miles 
  south 
  of 
  

   Ardmore, 
  the 
  Trinity 
  sands, 
  the 
  base 
  of 
  the 
  Comanche 
  series, 
  

   rest 
  unconformably 
  against 
  the 
  Carboniferous 
  (the 
  Red 
  beds 
  

   being 
  absent), 
  and 
  upon 
  these 
  in 
  turn 
  to 
  the 
  southward 
  the 
  

   sub-horizontal 
  beds 
  of 
  the 
  Lower 
  Cretaceous, 
  which 
  I 
  shall 
  

   make 
  the 
  subject 
  of 
  another 
  paper.* 
  

  

  A 
  parallel 
  north 
  and 
  south 
  section 
  twenty 
  miles 
  west 
  of 
  

   the 
  Santa 
  Fe 
  road 
  shows 
  the 
  presence 
  of 
  the 
  Red 
  beds 
  and 
  the 
  

   absence 
  of 
  the 
  Cretaceous, 
  the 
  latter 
  having 
  deflected 
  south- 
  

   ward 
  through 
  Texas. 
  

  

  It 
  is 
  not 
  alone 
  in 
  the 
  mountains 
  of 
  the 
  Paleozoic 
  areas, 
  how- 
  

   ever, 
  that 
  this 
  remarkable 
  vertical 
  structure 
  is 
  seen, 
  but 
  much 
  

   of 
  the 
  Carboniferous 
  prairie 
  regions 
  east 
  of 
  the 
  Red 
  beds 
  are 
  

   based 
  upon 
  it. 
  For 
  twenty 
  miles 
  north 
  from 
  the 
  Red 
  Bird 
  

   to 
  the 
  Arbuckle 
  Mountains 
  the 
  undulating 
  prairies, 
  void 
  of 
  

   any 
  high 
  relief 
  whatever, 
  except 
  slight 
  rises 
  where 
  the 
  sand- 
  

   stones 
  prevail, 
  are 
  based 
  upon 
  the 
  almost 
  vertical 
  Carboniferous 
  

   shales 
  and 
  sands, 
  as 
  shown 
  in 
  our 
  diagrams. 
  The 
  wonderful 
  

   degradation 
  these 
  folds 
  must 
  have 
  undergone 
  exceeds 
  all 
  possi- 
  

   bility 
  of 
  description. 
  Yet, 
  as 
  I 
  have 
  shown 
  in 
  my 
  Arkansas 
  re- 
  

   port, 
  there 
  are 
  many 
  miles 
  of 
  planed-ofl 
  folds 
  buried 
  beneath 
  the 
  

   Cretaceous 
  sediments. 
  This 
  is 
  the 
  only 
  instance 
  in 
  the 
  southwest 
  

   of 
  a 
  level 
  upland 
  plain 
  underlaid 
  by 
  vertical 
  structure. 
  The 
  

   great 
  unconformity 
  of 
  sedimentation 
  between 
  the 
  Silurian 
  rocks 
  

   and 
  the 
  supposed 
  base 
  of 
  the 
  Carboniferous 
  is 
  seen 
  both 
  at 
  Buck- 
  

   horn 
  on 
  the 
  northern 
  margin 
  of 
  the 
  Silurian 
  and 
  at 
  Hickory 
  

   Creek 
  near 
  Red 
  Bird 
  on 
  the 
  southern 
  side, 
  as 
  shown 
  by 
  differ- 
  

   ence 
  of 
  dip, 
  and 
  the 
  presence 
  of 
  conglomerates 
  in 
  contact 
  with 
  

   the 
  Silurian 
  rocks, 
  especially 
  at 
  the 
  last-named 
  place. 
  

  

  3. 
  The 
  Wichita 
  Division. 
  — 
  The 
  Arbuckle 
  folds 
  west 
  of 
  

   Duncan 
  are 
  buried 
  beneath 
  the 
  Red 
  beds 
  for 
  some 
  thirty 
  miles, 
  

   but 
  outcrop 
  again 
  some 
  eight 
  miles 
  north 
  of 
  Fort 
  Sill, 
  marking 
  

   the 
  northern 
  margin 
  of 
  the 
  Wichita 
  Mountains, 
  forming 
  a 
  low 
  

   foothill 
  which 
  is 
  comparatively 
  inconspicuous, 
  owing 
  to 
  the 
  

   overshadowing 
  height 
  and 
  sharpness 
  of 
  the 
  adjacent 
  eruptives 
  

   of 
  the 
  Wichita 
  Mountains 
  proper. 
  

  

  * 
  See 
  vol. 
  ii, 
  pp. 
  503-528, 
  Bulletin 
  Geological 
  Society 
  of 
  North 
  America. 
  

  

  