﻿266 
  EEPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  tance 
  through 
  a 
  low 
  red 
  sandstone 
  country. 
  At 
  the 
  southern 
  bend 
  of 
  

   the 
  river 
  the 
  Lower 
  Cretaceous 
  sandstones 
  are 
  exposed 
  — 
  about 
  150 
  feet 
  

   of 
  lirm 
  sandstones, 
  with 
  40 
  or 
  50 
  feet 
  of 
  variegated 
  beds 
  at 
  the 
  base. 
  

   Ten 
  or 
  twelve 
  miles 
  farther 
  up, 
  the 
  Eed 
  Beds 
  are 
  exposed 
  in 
  the 
  lower 
  

   part 
  of 
  the 
  canon-walls, 
  almost 
  to 
  the 
  base 
  of 
  the 
  Sierra 
  San 
  Miguel. 
  

   There 
  they 
  pass 
  beneath 
  the 
  Cretaceous 
  formations, 
  which 
  constitute 
  

   the 
  bulk 
  of 
  the 
  monutaius. 
  At 
  the 
  mouth 
  of 
  Bear 
  Eiver 
  there 
  are 
  1,000 
  

   feet 
  of 
  strata 
  exposed 
  or 
  i^artially 
  exposed. 
  Forming 
  the 
  upper 
  part 
  

   of 
  the 
  caiion-walls 
  are 
  200 
  feet 
  of 
  the 
  Upper 
  Dakota 
  sandstones; 
  

   beneath 
  these 
  are 
  some 
  700 
  feet 
  of 
  the 
  Lower 
  Dakota 
  Group 
  but 
  par- 
  

   tially 
  exposed, 
  and 
  at 
  the 
  base 
  are 
  about 
  100 
  feet 
  of 
  white, 
  pinkish, 
  and 
  

   red 
  massive, 
  cross-bedded 
  sandstone. 
  As 
  we 
  ascend 
  Bear 
  River 
  these 
  

   lower 
  sandstones 
  rise 
  gradually 
  until 
  at 
  the 
  entrance 
  of 
  the 
  La 
  Plata 
  

   branch, 
  11 
  miles 
  above, 
  they 
  occupy 
  the 
  greater 
  part 
  of 
  the 
  caiion- 
  

   walls. 
  

  

  Beyond 
  this 
  they 
  rise 
  more 
  rapidly, 
  and 
  extend 
  high 
  up 
  on 
  the 
  Carbon- 
  

   iferous 
  slopes 
  of 
  the 
  San 
  Juan 
  Mountains, 
  while 
  the 
  Cretaceous 
  forma- 
  

   tions 
  scarcely 
  appear 
  at 
  all 
  between 
  the 
  forks 
  of 
  the 
  Bear. 
  The 
  extreme 
  

   head 
  of 
  the 
  northern 
  branch 
  of 
  the 
  Bear 
  Eiver 
  is 
  in 
  the 
  eastern 
  end 
  of 
  

   the 
  San 
  Miguel 
  Mountains, 
  near 
  the 
  curious 
  needle-like 
  summit, 
  called 
  

   by 
  Mr. 
  Wilson 
  " 
  Lizard's 
  Head," 
  and 
  within 
  about 
  three 
  miles 
  of 
  San 
  

   Miguel 
  Lake. 
  This 
  is 
  in 
  the 
  Cretaceous 
  formations. 
  Farther 
  down, 
  

   under 
  the 
  east 
  base 
  of 
  the 
  Bear 
  Eiver 
  Mountains, 
  it 
  penetrates 
  to 
  the 
  

   Carboniferous 
  sandstones. 
  This 
  region 
  was 
  visited 
  by 
  Dr. 
  Endlich 
  in 
  

   1»74. 
  The 
  La 
  Plata 
  branch 
  rises 
  in 
  the 
  trachytes 
  and 
  Cretaceous 
  shales 
  

   on 
  the 
  northern 
  slopes 
  of 
  the 
  La 
  Plata 
  Mountains, 
  and 
  also 
  appears 
  to 
  

   penetrate 
  to 
  the 
  Carboniferous 
  sandstones. 
  The 
  walls 
  of 
  Lost 
  Canon 
  

   contain 
  nothing 
  but 
  Cretaceous 
  rocks. 
  

  

  Below 
  the 
  great 
  bend 
  of 
  the 
  Dolores 
  the 
  river 
  bed 
  sinks 
  rapidly 
  into 
  

   the 
  red 
  series, 
  but 
  about 
  fifteen 
  miles 
  farther 
  down 
  turns 
  so 
  much 
  to 
  

   the"~southwest 
  that 
  it 
  cuts 
  back 
  again 
  into 
  the 
  base 
  of 
  the 
  Lower 
  Dakota 
  

   Gi-oup. 
  On 
  turning 
  to 
  the 
  north 
  again 
  it 
  sinks 
  into 
  a 
  great 
  caiion, 
  

   which 
  has 
  as 
  yet 
  never 
  been 
  fully 
  explored. 
  

  

  The 
  Inter-Dolores 
  region, 
  called 
  on 
  our 
  maps 
  the 
  Dolores 
  Plateau, 
  

   still 
  retains 
  a 
  large 
  area 
  of 
  the 
  Middle 
  Cretaceous 
  shales, 
  and 
  a 
  portion 
  

   of 
  the 
  highest 
  part, 
  called 
  Lone 
  Mesa, 
  retains 
  a 
  capping 
  of 
  the 
  Upper 
  

   Cretaceous 
  sandstones. 
  This 
  mesa 
  rises 
  to 
  10,000 
  feet 
  above 
  the 
  sea, 
  

   and 
  covers 
  an 
  area 
  of 
  not 
  less 
  than 
  40 
  square 
  miles. 
  It 
  is 
  separated 
  

   from 
  a 
  similar 
  fragment 
  to 
  the 
  north 
  by 
  the 
  caiion 
  of 
  Disappointment 
  

   Creek. 
  Here 
  there 
  are 
  comi)lete 
  exposures 
  of 
  the 
  Middle 
  Cretaceous 
  

   strata, 
  and 
  lower 
  down 
  there 
  are 
  exposures 
  of 
  the 
  Dakota 
  sandstones. 
  

   South 
  and 
  west 
  of 
  Lone 
  Mesa 
  are 
  a 
  number 
  of 
  high 
  conical 
  and 
  flat- 
  

   topped 
  buttes, 
  from 
  which 
  the 
  Upper 
  Cretaceous 
  sandstones 
  have 
  been 
  

   removed. 
  On 
  the 
  summits 
  of 
  these 
  1 
  observed 
  numbers 
  of 
  rounded 
  

   basaltic 
  bowlders. 
  The 
  western 
  and 
  southern 
  borders 
  of 
  the 
  plateau 
  

   are 
  swept 
  pretty 
  clear 
  of 
  the 
  shales. 
  Forests 
  of 
  pine 
  and 
  fine 
  meadows 
  

   abound. 
  

  

  The 
  caiion 
  of 
  the 
  Dolores 
  is, 
  throughout 
  the 
  course, 
  as 
  far 
  as 
  examined 
  

   by 
  our 
  party, 
  very 
  narrow 
  and 
  precipitous. 
  The 
  alluvial 
  bottoms 
  are 
  

   seldom 
  wide 
  enough 
  to 
  admit 
  of 
  a 
  trail, 
  and 
  only 
  at 
  the 
  southern 
  bend 
  

   are 
  there 
  sufficient 
  areas 
  to 
  admit 
  of 
  agriculture. 
  Here 
  there 
  are 
  some 
  

   beautiful 
  spots. 
  Cottonwood-groves 
  and 
  many 
  varieties 
  of 
  bus'ies 
  and 
  

   vines 
  line 
  the 
  banks, 
  and 
  a 
  rich 
  growth 
  of 
  grass 
  covers 
  the 
  alluvial 
  

   flats.^ 
  On 
  the 
  borders 
  of 
  the 
  caiiou 
  below 
  there 
  is 
  a 
  pretty 
  heavy 
  growth 
  

   of 
  pinons, 
  cedars, 
  and 
  pines 
  ; 
  and 
  above, 
  on 
  the 
  various 
  branches 
  about 
  

   the 
  headwaters, 
  there 
  is 
  a 
  combination 
  of 
  forest 
  and 
  meadow, 
  of 
  pine 
  

  

  