﻿HATDEN.J 
  LETTER 
  TO 
  THE 
  SECRETARY. 
  7 
  

  

  mesa, 
  and 
  between 
  these 
  and 
  the 
  lower 
  sandstones. 
  Around 
  the 
  base 
  of 
  

   the 
  mesa, 
  the 
  Middle 
  Cretaceoas 
  shales 
  outcrop. 
  The 
  belt 
  covered 
  by 
  these 
  

   is 
  narrow, 
  and 
  is 
  followed 
  by 
  the 
  hard 
  sandstones 
  of 
  the 
  Dakota 
  group, 
  

   which 
  are 
  very 
  persistent 
  here 
  as 
  elsewhere, 
  and 
  occupy 
  the 
  higher 
  level 
  

   of 
  the 
  entire 
  mesa 
  country 
  to 
  the 
  west 
  and 
  north. 
  The 
  Jurassic 
  strata 
  

   and 
  the 
  "red 
  beds" 
  are 
  exposed 
  in 
  the 
  sides 
  and 
  bottoms 
  of 
  the 
  numer- 
  

   ous 
  canons 
  and 
  stream-courses, 
  the 
  latter 
  only 
  in 
  the 
  greater 
  valleys 
  and 
  

   in 
  patches 
  about 
  the 
  bases 
  of 
  the 
  trachytic 
  areas. 
  The 
  Jurassic 
  section 
  

   is, 
  in 
  the 
  upper 
  part, 
  almost 
  identical 
  with 
  the 
  corresponding 
  series 
  in 
  

   other 
  parts 
  of 
  Colorado, 
  but 
  at 
  the 
  base 
  has 
  a 
  larger 
  development 
  of 
  soft 
  

   sandstones 
  and 
  marls. 
  The 
  identiticatiou 
  rests 
  upon 
  the 
  analogy 
  of 
  

   position 
  and 
  lithology. 
  The 
  "red 
  beds" 
  are 
  massive 
  sandstones 
  and 
  

   conglomerates, 
  as 
  usual. 
  

  

  The 
  only 
  important 
  mountains 
  are 
  the 
  Sierra 
  La 
  Plata. 
  They 
  lie 
  to- 
  

   ward 
  the 
  northwest, 
  and 
  are 
  principally 
  of 
  Carboniferous 
  rocks, 
  so 
  highly 
  

   metamorphosed 
  as 
  to 
  have 
  lost 
  all 
  apparent 
  structure. 
  A 
  large 
  number 
  

   of 
  rich 
  lodes 
  of 
  gold 
  and 
  silver 
  have 
  been 
  recently 
  discovered 
  in 
  this 
  

   group 
  about 
  the 
  sources 
  of 
  the 
  Eio 
  La 
  Plata, 
  and 
  an 
  extensive 
  placer- 
  

   bar 
  is 
  located 
  near 
  the 
  exit 
  of 
  the 
  riv^er 
  from 
  the 
  mountains. 
  

  

  In 
  the 
  extreme 
  northeast 
  corner 
  of 
  this 
  district 
  is 
  a 
  group 
  of 
  trachytic 
  

   mountains, 
  including 
  Lone 
  Cone, 
  which 
  belongs 
  to 
  the 
  San 
  Miguel 
  

   Mountains. 
  West 
  of 
  the 
  Mesa 
  Yerde, 
  almost 
  .in 
  the 
  center 
  of 
  the 
  dis- 
  

   trict, 
  stands 
  the 
  " 
  Late" 
  group, 
  of 
  which 
  Ute 
  Peak 
  is 
  the 
  culminating 
  

   summit. 
  It 
  covers 
  an 
  area 
  of 
  some 
  forty 
  square 
  miles, 
  and 
  is 
  simply 
  a 
  

   mass 
  of 
  trachyte 
  pushed 
  up 
  through 
  and 
  poured 
  out 
  over 
  the 
  floor 
  of 
  the 
  

   Dakota 
  group. 
  

  

  In 
  the 
  extreme 
  southwest 
  corner, 
  principally 
  in 
  Arizona, 
  is 
  the 
  

   Sierra 
  Carriso, 
  identical 
  with 
  the 
  Late 
  in 
  nearly 
  every 
  respect, 
  differing 
  

   only 
  in 
  having 
  carried 
  up 
  portions 
  of 
  the 
  Carboniferous 
  rocks 
  about 
  

   the 
  base, 
  while 
  a 
  fragment 
  of 
  the 
  same 
  formation 
  is 
  caught 
  up 
  in 
  the 
  

   center 
  of 
  the 
  group. 
  

  

  Of 
  the 
  G,000 
  square 
  miles, 
  5,700 
  are 
  of 
  sedimentary 
  rocks: 
  230 
  of 
  these 
  

   in 
  the 
  southeast 
  are 
  of 
  the 
  so-called 
  Lignitic; 
  800, 
  chiefly 
  included 
  in 
  

   the 
  Mesa 
  Verde, 
  belong 
  to 
  the 
  Upper 
  Cretaceous 
  ; 
  and 
  the 
  remaining 
  

   4,900 
  to 
  the 
  Lower 
  Cretaceous, 
  and 
  such 
  of 
  the 
  earlier 
  periods 
  as 
  are 
  

   exposed 
  in 
  the 
  crooked 
  and 
  narrow 
  valleys, 
  and 
  about 
  the 
  trachytic 
  

   groups. 
  In 
  the 
  Cretaceous 
  series, 
  Mr. 
  Holmes 
  examined 
  a 
  number 
  of 
  

   seams 
  of 
  workable 
  coal, 
  procured 
  fossils 
  in 
  ten 
  distinct 
  horizons, 
  and 
  

   expects 
  to 
  be 
  able 
  to 
  identify 
  these 
  horizons 
  with 
  such 
  corresponding 
  

   ones 
  as 
  exist 
  on 
  the 
  Atlantic 
  slope. 
  The 
  section 
  obtained 
  is 
  the 
  most 
  

   complete 
  and 
  satisfactory 
  made 
  in 
  Colorado 
  up 
  to 
  this 
  time. 
  The 
  tra- 
  

   chyte 
  areas 
  include 
  about 
  250 
  square 
  miles, 
  and 
  seem 
  to 
  present 
  many 
  

   remarkable 
  and 
  interesting 
  features. 
  

  

  The 
  prehistoric 
  remains 
  in 
  the 
  caiions 
  and 
  lowlands 
  of 
  the 
  Southwest 
  

   are 
  of 
  great 
  interest, 
  and 
  the 
  study 
  of 
  them 
  by 
  Mr. 
  Holmes 
  was 
  as 
  com- 
  

   plete 
  as 
  possible 
  under 
  the 
  circumstances. 
  Many 
  cliff-houses, 
  built 
  in 
  

  

  