﻿Ouachita 
  Mountain 
  System 
  in 
  Indian 
  Territory. 
  117 
  

  

  Mr. 
  Chance's 
  map. 
  Several 
  sigmoid 
  or 
  S-shaped 
  flexures 
  occur 
  

   along 
  this 
  section, 
  and, 
  also, 
  in 
  the 
  sandstones 
  of 
  the 
  Coal 
  

   Measures 
  of 
  eastern 
  Indian 
  Territory 
  and 
  across 
  the 
  Territory 
  

   to 
  the 
  Arkansas 
  line. 
  

  

  The 
  southern 
  border 
  of 
  this 
  old 
  system 
  has 
  been 
  degraded* 
  

   by 
  the 
  shore 
  lines 
  of 
  the 
  ancient 
  Cretaceous 
  and 
  Tertiary 
  seas 
  

   which 
  overlapped 
  it 
  and 
  planed 
  it 
  northward 
  for 
  many 
  miles. 
  

   The 
  vertical 
  edges 
  of 
  the 
  planed 
  off 
  strata 
  are 
  buried 
  beneath 
  

   the 
  Cretaceous 
  sediments 
  as 
  shown 
  in 
  my 
  former 
  section 
  along 
  

   the 
  Arkansas-Texas 
  line, 
  resulting 
  in 
  the 
  complete 
  interment 
  

   of 
  the 
  Carboniferous 
  system 
  southward, 
  throughout 
  the 
  great 
  

   central 
  denuded 
  region 
  of 
  Texas 
  where 
  the 
  only 
  exposures 
  of 
  

   Carboniferous 
  rocks 
  are 
  through 
  erosion 
  of 
  the 
  overlying 
  Cre- 
  

   taceous 
  layers. 
  The 
  structure 
  of 
  these 
  mountains 
  is 
  of 
  the 
  

   Appalachian 
  type, 
  and 
  Mr. 
  Chance 
  says 
  that 
  " 
  topographically 
  

   and 
  structurally 
  the 
  Choctaw 
  coal 
  fields 
  represent 
  in 
  miniature 
  

   the 
  features 
  of 
  the 
  anthracite 
  regions 
  of 
  Pennsylvania." 
  

  

  2. 
  The 
  Central 
  or 
  Chickasaw 
  Division. 
  — 
  In 
  the 
  northeastern 
  

   part 
  of 
  the 
  Chickasaw 
  nation 
  the 
  continuity 
  of 
  the 
  Carbonif- 
  

   erous 
  rocks 
  is 
  terminated 
  by 
  an 
  extensive 
  area 
  of 
  Silurian 
  lime- 
  

   stones, 
  which, 
  in 
  turn, 
  are 
  succeeded 
  southward 
  by 
  underlying 
  

   granites 
  whose 
  exact 
  relation 
  to 
  the 
  complicated 
  Coal 
  Measures 
  

   is 
  not 
  determined, 
  but 
  which 
  are 
  exposed 
  by 
  the 
  erosion 
  of 
  the 
  

   latter 
  and 
  are 
  ^unconformable 
  beneath 
  them. 
  

  

  2a. 
  The 
  Eastern 
  or 
  Wape?iucha 
  portion 
  of 
  this 
  area 
  is 
  inter- 
  

   esting, 
  but 
  little 
  explored. 
  It 
  lies 
  west 
  of 
  Boggy 
  station 
  along 
  

   Delaware 
  Creek 
  at 
  Bill 
  Jackson's 
  ranch, 
  and 
  near 
  the 
  quaint 
  

   old 
  Chickasaw 
  academy 
  of 
  Wapenucka. 
  There 
  is 
  a 
  series 
  of 
  

   low 
  limestone 
  hills 
  — 
  apparently 
  remnants 
  of 
  anticlinal 
  folds 
  — 
  

   along 
  whose 
  strike 
  flows 
  the 
  Delaware 
  creek. 
  In 
  places 
  these 
  

   limestones 
  resemble 
  the 
  blue 
  Silurian 
  limestone 
  to 
  be 
  described 
  

   in 
  our 
  discussion 
  of 
  the 
  Arbuckle 
  Mountains, 
  but 
  they 
  are 
  

   more 
  horizontal 
  in 
  outcrop. 
  In 
  the 
  collection 
  of 
  Mr. 
  J. 
  T. 
  

   Munson, 
  of 
  Denison, 
  who 
  first 
  called 
  my 
  attention 
  to 
  this 
  in- 
  

   teresting 
  region, 
  are 
  fossils 
  apparently 
  Silurian 
  in 
  age 
  Ortho- 
  

   ceras 
  and 
  Brachiopoda, 
  from 
  Bill 
  Jackson's 
  ranch 
  on 
  the 
  Dela- 
  

   ware.f 
  

  

  Crinoidal 
  limestones 
  of 
  Carboniferous 
  age 
  are 
  the 
  prevalent 
  

   rocks 
  and 
  were 
  collected 
  near 
  the 
  academy 
  at 
  the 
  southern 
  

   border 
  of 
  the 
  district, 
  and 
  the 
  sandstones 
  of 
  apparent 
  Carbon- 
  

   iferous 
  age 
  and 
  shales 
  of 
  that 
  age 
  begin 
  there 
  again. 
  A 
  single 
  

   specimen 
  of 
  Favosites, 
  of 
  Silurian 
  age, 
  was 
  collected 
  from 
  one 
  

  

  * 
  Principal 
  Events 
  in 
  North 
  American 
  Cretaceous 
  History 
  as 
  revealed 
  in 
  the 
  

   Arkansas-Texas 
  Region, 
  by 
  Robt. 
  T. 
  Hill. 
  This 
  Journal, 
  April, 
  1889. 
  

  

  f 
  Professor 
  Alpheus 
  Hyatt, 
  to 
  whom 
  I 
  sent 
  this 
  specimen, 
  says 
  that 
  he 
  thinks 
  

   there 
  is 
  little 
  doubt 
  that 
  it 
  is 
  a 
  fragment 
  from 
  the 
  Hudson 
  River 
  group. 
  The 
  Or- 
  

   thoceras 
  being 
  closely 
  related 
  to 
  one 
  found 
  at 
  Cincinnati, 
  and 
  the 
  brachiopod 
  

   being 
  probably 
  Orthis 
  testudinaria. 
  

  

  