﻿CHAPTER 
  III. 
  

  

  SURFACE 
  GEOLOGY— 
  SAN 
  MIGUEL 
  AND 
  DOLORES 
  RIVERS— 
  

   UNAWEEP 
  CANON— 
  SIERRA 
  LA 
  SAL 
  AND 
  GRAND 
  RIVER. 
  

  

  Under 
  the 
  heading 
  San 
  Miguel 
  River 
  I 
  shall 
  take 
  up 
  the 
  plateau 
  that 
  

   borders 
  the 
  river, 
  to 
  which 
  the 
  name 
  San 
  Miguel 
  plateau 
  has 
  been 
  given, 
  

   and 
  also 
  the 
  western 
  crest 
  of 
  the 
  Uncompahgre 
  plateau 
  where 
  it 
  overlooks 
  

   the 
  San 
  Miguel 
  plateau. 
  

  

  Under 
  the 
  second 
  heading, 
  "Dolores 
  River," 
  I 
  shall 
  consider 
  the 
  re- 
  

   gion 
  lying 
  between 
  the 
  Dolores 
  River 
  and 
  the 
  crest 
  of 
  the 
  Uncompah- 
  

   gre 
  plateau. 
  The 
  country 
  between 
  the 
  San 
  Miguel 
  and 
  the 
  Dolores 
  was 
  

   uncompleted, 
  owing 
  to 
  the 
  interruption 
  of 
  our 
  work 
  by 
  the 
  Indians, 
  and 
  

   we 
  were 
  able 
  to 
  obtain 
  only 
  a 
  general 
  idea 
  of 
  it 
  from 
  glimpses 
  of 
  it 
  ob- 
  

   tained 
  from 
  the 
  crest 
  of 
  the 
  Uncompahgre 
  plateau, 
  the 
  Sierra 
  la 
  Sal, 
  and 
  

   from 
  Lone 
  Cone. 
  The 
  third 
  heading 
  will 
  be 
  "Unaweep 
  Canon." 
  

  

  The 
  fourth 
  division 
  of 
  the 
  chapter, 
  " 
  Sierra 
  la 
  Sal 
  and 
  Grand 
  River," 
  

   will 
  be 
  devoted 
  to 
  the 
  country 
  drained 
  by 
  the 
  streams 
  radiating 
  from 
  the 
  

   Sierra 
  la 
  Sal. 
  

  

  SAN 
  MIGUEL 
  RIVER. 
  

  

  The 
  San 
  Miguel 
  is 
  a 
  branch 
  of 
  the 
  Dolores, 
  to 
  which, 
  above 
  the 
  junc- 
  

   tion, 
  it 
  is 
  equal 
  in 
  size 
  and 
  in 
  the 
  amount 
  of 
  water 
  carried. 
  It 
  rises 
  in 
  

   the 
  extreme 
  northwestern 
  part 
  of 
  the 
  San 
  Juan 
  Mountains, 
  opposite 
  the 
  

   sources 
  of 
  the 
  Dolores, 
  Animas, 
  and 
  Uncompahgre 
  Rivers. 
  In 
  this 
  re- 
  

   gion 
  it 
  is 
  formed 
  by 
  two 
  streams, 
  one 
  flowing 
  north 
  and 
  the 
  other 
  west. 
  

   Both 
  rise 
  in 
  the 
  midst 
  of 
  volcanic 
  rocks, 
  which 
  they 
  soon 
  leave, 
  flowing 
  

   out 
  ioto 
  the 
  sedimentary 
  formations, 
  mainly 
  Cretaceous 
  shales. 
  After 
  

   the 
  union 
  of 
  the 
  two 
  streams 
  the 
  river 
  flows 
  toward 
  the 
  northwest, 
  grad- 
  

   ually 
  emerging 
  from 
  the 
  mountains 
  and 
  cutting 
  through 
  the 
  Middle 
  

   Cretaceous, 
  the 
  Dakota 
  group, 
  the 
  Jurassic 
  shales, 
  and 
  the 
  upper 
  part 
  

   of 
  the 
  red 
  beds. 
  The 
  river 
  is 
  in 
  a 
  caiion 
  1,600 
  to 
  2,000 
  feet 
  in 
  depth. 
  

   In 
  this 
  upper 
  portion 
  of 
  the 
  river 
  there 
  are 
  placer 
  bars 
  which 
  are 
  being 
  

   worked 
  to 
  considerable 
  extent. 
  

  

  Emerging 
  from 
  the 
  mountains, 
  the 
  San 
  Miguel 
  flows 
  out 
  into 
  the 
  

   San 
  Miguel 
  Plateau, 
  keeping 
  in 
  a 
  narrow 
  canon 
  averaging 
  about 
  1,000 
  

   feet 
  in 
  depth. 
  The 
  course 
  of 
  the 
  river 
  for 
  about 
  twenty-live 
  miles 
  fVom 
  

   the 
  mountains 
  is 
  about 
  northwest. 
  It 
  then 
  turns 
  to 
  the 
  westward 
  for 
  

   about 
  eight 
  miles 
  ; 
  then 
  flows 
  to 
  the 
  southwest 
  for 
  about 
  eight 
  miles 
  

   more, 
  and 
  finally 
  for 
  about 
  twenty-two 
  miles 
  has 
  a 
  course 
  northwest 
  to 
  

   its 
  mouth 
  in 
  the 
  Dolores. 
  The 
  prevailing 
  formation 
  on 
  both 
  sides 
  of 
  the 
  

   river 
  is 
  the 
  massive 
  sandstone, 
  forming 
  the 
  upper 
  part 
  of 
  the 
  Dakota 
  

   group, 
  (Cretaceous 
  No. 
  1.) 
  In 
  the 
  caQon, 
  toward 
  the 
  upper 
  part 
  of 
  the 
  

   river, 
  the 
  red 
  beds 
  show, 
  but 
  as 
  wefollow 
  down 
  the 
  stream 
  theoutcrop 
  sinks 
  

   and 
  we 
  have 
  only 
  a 
  narrow 
  belt 
  of 
  the 
  Jurassic 
  shales 
  below 
  the 
  Dakota 
  

   group 
  bordering 
  the 
  river. 
  There 
  is 
  but 
  little 
  river-bottom, 
  and 
  the 
  

   stream 
  winds 
  but 
  little 
  in 
  its 
  course. 
  On 
  the 
  southwest 
  side 
  of 
  the 
  river 
  

  

  51 
  

  

  