﻿Stratigraphy 
  of 
  Eastern 
  New 
  Mexico. 
  125 
  

  

  mands 
  a 
  more 
  careful, 
  detailed, 
  and 
  regional 
  study 
  than 
  

   the 
  writer 
  has 
  been 
  able 
  to 
  make 
  in 
  this 
  exploration. 
  

  

  There 
  has 
  been 
  a 
  truly 
  immense 
  amount 
  of 
  erosion, 
  

   accomplished 
  during 
  the 
  latter 
  half 
  of 
  the 
  Cenozoic. 
  

   Three 
  factors 
  have 
  probably 
  combined 
  to 
  bring 
  about 
  the 
  

   subaerial 
  denudation: 
  (1) 
  the 
  comparatively 
  non-resist- 
  

   ant 
  nature 
  of 
  almost 
  all 
  the 
  sedimentary 
  rocks 
  later 
  in 
  

   age 
  than 
  the 
  Magdalena; 
  (2) 
  great 
  elevation 
  of 
  the 
  

   mountain 
  ranges 
  and 
  surrounding 
  plains, 
  affording 
  steep 
  

   gradients 
  ; 
  and 
  (3) 
  arid 
  or 
  semi-arid 
  climate 
  with 
  sporadic 
  

   cloudburst 
  precipitation 
  and 
  a 
  sparse 
  vegetal 
  covering. 
  

   Proof 
  has 
  been 
  given 
  elsewhere 
  3 
  that 
  the 
  upper 
  surface 
  

   of 
  the 
  High 
  Plains 
  and 
  Llano 
  Estacado 
  extended 
  west- 
  

   ward 
  with, 
  in 
  all 
  probability, 
  gradually 
  increasing 
  alti- 
  

   tude 
  as 
  late 
  as 
  early 
  Pleistocene 
  times. 
  An 
  average 
  rock 
  

   thickness' 
  of 
  at 
  least 
  1500 
  feet 
  has 
  been 
  removed 
  from 
  the 
  

   region 
  between 
  Tucumcari 
  and 
  the 
  southern 
  Rocky 
  Moun- 
  

   tains 
  in 
  the 
  later 
  Pleistocene. 
  

  

  Extrusion 
  of 
  basalt 
  has 
  occurred 
  since 
  the 
  date 
  of 
  for- 
  

   mation 
  of 
  the 
  major 
  features 
  of 
  the 
  present 
  topography. 
  

   The 
  basalt 
  flows 
  of 
  the 
  northern 
  Tularosa 
  Basin 
  and 
  from 
  

   Maxon 
  Crater 
  down 
  the 
  Mora 
  River 
  valley 
  into 
  the 
  val- 
  

   ley 
  of 
  the 
  Canadian 
  have 
  taken 
  place 
  in 
  Recent 
  times. 
  

  

  List 
  of 
  Orogenic 
  Epochs 
  in 
  Eastern 
  New 
  Mexico. 
  

  

  1. 
  Pre-Cambrian 
  ; 
  intense 
  folding, 
  faulting 
  and 
  meta- 
  

  

  morphism. 
  

  

  2. 
  Pre-Magdalena 
  ; 
  possibly 
  of 
  the 
  nature 
  of 
  a 
  broad 
  

  

  warping 
  confined 
  to 
  the 
  southern 
  Rocky 
  Mountains 
  

   (Sangre 
  de 
  Cristo 
  Range). 
  

  

  3. 
  Upper 
  Pennsylvanian 
  (Pre-Abo) 
  ; 
  gentle 
  folding 
  in 
  

  

  the 
  regions 
  of 
  all 
  present 
  mountain 
  uplifts. 
  May 
  

   also 
  have 
  affected 
  most 
  of 
  the 
  present 
  plains 
  area, 
  

   where 
  the 
  older 
  rocks 
  are 
  now 
  concealed. 
  

  

  4. 
  Pre-Upper 
  Triassic; 
  gentle 
  folding 
  or 
  warping 
  of 
  

  

  probably 
  entire 
  region 
  and 
  almost 
  certainly 
  a 
  large 
  

   uplift 
  of 
  the 
  southern 
  region 
  of 
  the 
  present 
  Rocky 
  

   Mountain 
  system. 
  

  

  5. 
  Laramide 
  (near 
  end 
  of 
  Cretaceous) 
  ; 
  perhaps 
  con- 
  

  

  fined 
  to 
  region 
  of 
  present 
  Rocky 
  Mountain 
  system. 
  

  

  6. 
  Mid-Tertiary 
  (probably 
  late 
  Middle 
  Miocene) 
  ; 
  affect- 
  

  

  ing 
  the 
  region 
  of 
  present 
  mountain 
  ranges 
  of 
  north- 
  

  

  3 
  Op. 
  cit. 
  

  

  