﻿GEOLOGICAL 
  REPORT 
  ON 
  THE 
  GRAND 
  RIVER 
  DISTRICT. 
  

  

  CHAPTER 
  I. 
  

  

  GENERAL 
  INTRODUCTION. 
  

  

  The 
  district 
  assigned 
  the 
  northern 
  or 
  Grand 
  Eiver 
  division 
  for 
  the 
  

   season 
  of 
  1875, 
  lies 
  between 
  the 
  parallels- 
  of 
  latitude 
  37° 
  52' 
  and 
  39° 
  15'. 
  

   On 
  the 
  west 
  it 
  is 
  limited 
  by 
  the 
  meridian 
  109° 
  30' 
  and 
  on 
  the 
  east 
  by 
  the 
  

   western 
  limit 
  of 
  the 
  work 
  of 
  1874, 
  which 
  is 
  approximately 
  the 
  Gun- 
  

   nison 
  and 
  Uncompahgre 
  Elvers. 
  In 
  addition 
  to 
  this 
  there 
  is 
  a 
  narrow 
  

   strip 
  of 
  country 
  south 
  of 
  the 
  Gunnison 
  Eiver, 
  from 
  10 
  to 
  20 
  miles 
  in 
  

   width, 
  extending 
  from 
  meridian 
  107° 
  to 
  107° 
  30'. 
  This 
  lies 
  between 
  our 
  

   work 
  of 
  1874 
  and 
  Mr. 
  Wilson's 
  for 
  the 
  same 
  season. 
  The 
  entire 
  area 
  in- 
  

   cludes 
  about 
  7,900 
  square 
  miles, 
  of 
  which, 
  owing 
  to 
  interruption 
  of 
  work 
  

   by 
  the 
  Indians, 
  the 
  survey 
  of 
  only 
  6,000 
  square 
  miles 
  was 
  completed. 
  

   Of 
  this, 
  about 
  1,500 
  square 
  miles 
  are 
  in 
  the 
  southwestern 
  corner, 
  and 
  

   500 
  north 
  of 
  Grand 
  Eiver. 
  

  

  The 
  drainage 
  of 
  the 
  district 
  has 
  two 
  general 
  directions, 
  viz, 
  north- 
  

   west 
  and 
  southwest. 
  All 
  the 
  streams 
  are 
  tributary 
  to 
  the 
  Grand 
  Eiver, 
  

   which 
  is 
  one 
  of 
  the 
  forks 
  of 
  the 
  Colorado 
  Eiver 
  of 
  the 
  West. 
  The 
  greater 
  

   part 
  of 
  the 
  district 
  is 
  plateau 
  in 
  character 
  ; 
  the 
  Sierra 
  la 
  Sal 
  being 
  the 
  

   only 
  mountain 
  group. 
  The 
  Lone 
  Cone 
  group 
  lies 
  in 
  the 
  district 
  to 
  the 
  

   south, 
  and 
  will 
  be 
  fully 
  described 
  in 
  Mr. 
  Holmes's 
  report 
  for 
  1876. 
  

  

  The 
  La 
  Sal 
  Mountains 
  consist 
  of 
  three 
  groups 
  of 
  isolated 
  peaks, 
  about 
  

   thirty 
  in 
  number, 
  forming 
  a 
  range 
  about 
  fifteen 
  miles 
  long 
  and 
  five 
  miles 
  

   in 
  width 
  ; 
  its 
  general 
  direction 
  is 
  about 
  north 
  and 
  south. 
  The 
  drainage 
  

   radiates 
  from 
  the 
  mountains, 
  the 
  streams 
  on 
  the 
  south 
  and 
  east 
  flowing 
  

   into 
  the 
  Dolores, 
  while 
  those 
  on 
  the 
  north 
  and 
  west 
  flow 
  directly 
  into 
  

   the 
  Grand. 
  

  

  The 
  Abajo 
  Mountains 
  are 
  partly 
  in 
  and 
  partly 
  outside 
  of 
  the 
  district, 
  

   lying 
  in 
  the 
  extreme 
  southwest 
  corner. 
  On 
  account 
  of 
  the 
  interruption 
  

   of 
  our 
  work 
  by 
  the 
  Indians, 
  they 
  were 
  not 
  visited. 
  Excluding 
  the 
  moun- 
  

   tain 
  masses, 
  which 
  will 
  probably 
  not 
  exceed 
  100 
  square 
  miles 
  in 
  extent, 
  

   the 
  range 
  in 
  elevation 
  is 
  from 
  4,000 
  to 
  over 
  9,000 
  feet. 
  A 
  compara- 
  

   tively 
  small 
  proportion 
  of 
  the 
  country 
  is 
  fitted 
  for 
  agricultural 
  purposes, 
  

   farming 
  lancl 
  being 
  confined 
  to 
  portions 
  of 
  the 
  valleys 
  of 
  the 
  Uncom- 
  

   pahgre 
  and 
  Gunnison 
  Elvers, 
  and 
  to 
  some 
  small 
  valleys 
  on 
  the 
  upper 
  

   part 
  of 
  the 
  Dolores, 
  and 
  a 
  few 
  of 
  the 
  streams 
  draining 
  the 
  Sierra 
  la 
  Sal. 
  

  

  As 
  already 
  stated, 
  a 
  great 
  part 
  of 
  the 
  district 
  is 
  plateau-like. 
  The 
  

   levels 
  are, 
  however, 
  above 
  that 
  of 
  the 
  streams 
  ; 
  the 
  latter 
  cutting 
  deep 
  

   <T,nd, 
  in 
  some 
  places, 
  impassable 
  caiious, 
  which, 
  with 
  the 
  exception 
  of 
  

   those 
  occupied 
  by 
  the 
  main 
  streams, 
  are 
  dry 
  the 
  greater 
  part 
  of 
  the 
  

   year. 
  They 
  cut 
  the 
  plateaus 
  into 
  mesas. 
  In 
  another 
  part 
  of 
  this 
  report 
  

  

  33 
  

   3 
  G 
  s 
  

  

  