﻿58 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  there 
  is 
  a 
  slight 
  slope 
  to 
  the 
  Dolores, 
  i. 
  e., 
  toward 
  the 
  southwest. 
  Be- 
  

   yond 
  the 
  Dolores 
  the 
  dip 
  is 
  reversed. 
  On 
  the 
  north 
  side 
  of 
  the 
  creek, 
  

   rising' 
  south 
  of 
  station 
  47, 
  the 
  dip 
  is 
  west 
  and 
  northwest. 
  When 
  we 
  

   cross 
  the 
  Dolores, 
  opposite 
  the 
  mouth 
  of 
  this 
  creek, 
  as 
  we 
  shall 
  see 
  in 
  

   another 
  part 
  of 
  this 
  chapter, 
  there 
  is 
  a 
  marked 
  dip 
  to 
  the 
  north. 
  

  

  From 
  station 
  47 
  we 
  could 
  trace 
  the 
  crest 
  about 
  six 
  miles 
  to 
  the 
  north- 
  

   west. 
  Beyond 
  this 
  point 
  we 
  were 
  unable 
  to 
  work. 
  It 
  is 
  probable 
  that 
  

   the 
  granitic 
  rock 
  extends 
  but 
  little 
  farther 
  in 
  that 
  direction, 
  but 
  instead 
  

   turns 
  to 
  the 
  eastward. 
  There 
  is 
  a 
  gap 
  in 
  the 
  work 
  here 
  between 
  the 
  

   crest 
  and 
  Grand 
  Eiver, 
  the 
  crest 
  being 
  too 
  far 
  from 
  the 
  river 
  to 
  get 
  

   details, 
  and 
  our 
  trouble 
  with 
  the 
  Indians 
  preventing 
  our 
  going 
  there 
  

   later 
  in 
  the 
  season, 
  as 
  we 
  had 
  intended 
  when 
  working 
  in 
  this 
  part 
  of 
  the 
  

   district. 
  From 
  Sierra 
  la 
  Sal 
  we 
  could 
  see 
  a 
  line 
  of 
  what 
  we 
  took 
  to 
  be 
  

   an 
  outcrop 
  of 
  Jurassic 
  strata, 
  but 
  the 
  distance 
  was 
  too 
  great 
  to 
  be 
  ab- 
  

   solutely 
  certain. 
  

  

  UNAWEEP 
  CANON. 
  

  

  Ashas 
  been 
  already 
  noted, 
  the 
  Unaweep 
  Caiion 
  has 
  two 
  streams, 
  one 
  

   flowing 
  to 
  the 
  Gunnison 
  and 
  the 
  other 
  to 
  the 
  Dolores. 
  The 
  divide 
  

   between 
  them 
  is 
  1,200 
  feet 
  below 
  the 
  general 
  level 
  of 
  the 
  country 
  and 
  

   2,400 
  feet 
  above 
  their 
  mouths, 
  and 
  the 
  width 
  of 
  the 
  canon 
  from 
  half 
  a 
  

   mile 
  to 
  a 
  mile. 
  It 
  is 
  a 
  caiion 
  of 
  erosion. 
  There 
  is 
  no 
  displacement 
  of 
  

   the 
  rocks. 
  Gneiss 
  or 
  granite 
  underlies 
  the 
  valley, 
  as 
  is 
  seen 
  at 
  both 
  

   ends, 
  although 
  in 
  the 
  center 
  it 
  is 
  concealed 
  by 
  the 
  local 
  drift. 
  Resting 
  

   on 
  the 
  Archaean 
  rocks 
  are 
  the 
  Triassic 
  red 
  sandstones, 
  preserving 
  the 
  

   same 
  level 
  on 
  both 
  sides 
  of 
  the 
  caiion. 
  The 
  two 
  creeks 
  that 
  at 
  present 
  

   occu])y 
  the 
  caiion 
  are 
  obviously 
  insufficient 
  to 
  account 
  for 
  the 
  erosion 
  

   implied 
  by 
  the 
  width 
  and 
  depth 
  of 
  the 
  gorge. 
  Some 
  large 
  stream 
  must 
  

   once 
  have 
  occupied 
  it. 
  Several 
  interesting 
  questions 
  at 
  once 
  arise, 
  viz 
  : 
  

   What 
  direction 
  did 
  it 
  flow 
  ? 
  Was 
  it 
  the 
  Gunnison, 
  Grand, 
  or 
  the 
  Dolores? 
  

   Why 
  was 
  it 
  turned 
  aside 
  ? 
  It 
  is 
  impossible, 
  with 
  the 
  limited 
  data 
  at 
  

   command, 
  to 
  answer 
  these 
  queries. 
  I 
  shall 
  simply 
  content 
  myself 
  with 
  

   suggesting 
  certain, 
  points 
  that 
  present 
  themselves 
  to 
  my 
  mind 
  in 
  regard 
  

   to 
  it. 
  

  

  lu 
  the 
  first 
  place, 
  let 
  me 
  regard 
  the 
  canon 
  as 
  the 
  old 
  bed 
  of 
  the 
  Dolores, 
  

   through 
  which 
  it 
  flowed 
  to 
  join 
  the 
  Gnnnison. 
  

  

  Of 
  the 
  two 
  creeks 
  draining 
  the 
  caiion, 
  the 
  one 
  flowing 
  into 
  the 
  Gunni- 
  

   son 
  is 
  the 
  most 
  inconsiderable. 
  Its 
  fall 
  per 
  mile 
  for 
  the 
  first 
  eight 
  miles 
  

   of 
  its 
  course 
  is 
  105 
  feet. 
  On 
  the 
  other 
  side, 
  for 
  the 
  same 
  distance, 
  the 
  

   rate 
  of 
  fall 
  is 
  about 
  46 
  feet 
  per 
  mile, 
  although 
  a 
  greater 
  quantity 
  of 
  

   water 
  is 
  carried 
  by 
  West 
  Creek. 
  

  

  The 
  first 
  few 
  miles 
  on 
  either 
  side 
  of 
  the 
  divide 
  present 
  the 
  most 
  strik- 
  

   ing 
  difference. 
  On 
  the 
  east 
  it 
  is 
  80 
  feet 
  per 
  mile, 
  while 
  on 
  the 
  west 
  

   there 
  is 
  little, 
  if 
  any, 
  difference 
  — 
  11 
  feet 
  being 
  the 
  entire 
  amount 
  of 
  fall 
  

   two 
  and 
  a 
  half 
  miles 
  west 
  of 
  the 
  divide. 
  For 
  three 
  and 
  a 
  half 
  miles 
  

   beyond 
  this 
  the 
  rate 
  is 
  about 
  05 
  feet. 
  Beyond, 
  however, 
  where 
  the 
  

   caiion 
  is 
  narrow, 
  the 
  fall 
  is 
  very 
  much 
  greater. 
  The 
  figures 
  just 
  given 
  

   would 
  seem 
  to 
  imply 
  that 
  the 
  original 
  bed 
  of 
  the 
  caiion 
  sloped 
  to 
  the 
  

   eastward. 
  We 
  must 
  remember, 
  however, 
  that 
  the 
  elevation 
  of 
  the 
  

   plateau 
  probably 
  continued 
  after 
  the 
  caiion 
  was 
  drained. 
  If 
  the 
  Dolores 
  

   did 
  flow 
  througli 
  the 
  caiion, 
  we 
  have 
  to 
  presume 
  that 
  its 
  present 
  course 
  

   was 
  caused 
  partly 
  by 
  the 
  rising 
  of 
  the 
  Uncompahgre 
  plateau 
  and 
  partly 
  

   by 
  the 
  elevation 
  of 
  the 
  Sierra 
  la 
  Sal, 
  the 
  former 
  cutting 
  it 
  off 
  from 
  the 
  

   Unaweep 
  Caiion, 
  and 
  the 
  latter 
  providing 
  a 
  depression 
  in 
  which 
  it 
  has 
  

   cut 
  its 
  present 
  caiion. 
  Against 
  the 
  theory 
  are 
  the 
  following 
  points 
  : 
  

  

  1st. 
  The 
  great 
  rate 
  of 
  fall 
  in 
  the 
  caiion 
  as 
  it 
  crosses 
  the 
  crest 
  of 
  the 
  

  

  