﻿ENDUCH.] 
  SAWATCH 
  RANGE 
  — 
  DRIFT. 
  171 
  

  

  strata 
  analogous 
  with 
  those 
  described 
  from 
  the 
  Eio 
  Grande 
  Pyramid,* 
  

   and 
  identical 
  with 
  those 
  quoted 
  as 
  occurring 
  farther 
  south. 
  The 
  rock 
  

   composing 
  these 
  strata 
  weathers 
  into 
  small 
  fragments 
  that 
  can 
  almost 
  

   deserve 
  tbe 
  name 
  of 
  gravel, 
  and 
  cover 
  the 
  rounded 
  surface 
  of 
  the 
  ridges 
  

   leading 
  up 
  to 
  the 
  plateau. 
  This 
  latter 
  shows 
  the 
  same 
  features 
  as 
  farther 
  

   south. 
  Small 
  lakelets 
  and 
  swamps 
  change 
  with 
  either 
  grassy 
  slopes 
  or 
  

   immense 
  fields 
  of 
  angular 
  bowlders. 
  Both 
  are 
  characteristic 
  of 
  the 
  plat- 
  

   eau, 
  and 
  are 
  found 
  wherever 
  it 
  has 
  retained 
  its 
  nature 
  as 
  such. 
  By 
  

   way 
  of 
  Weeminuche 
  Pass 
  we 
  cross 
  the 
  continental 
  divide, 
  and 
  are 
  once 
  

   more 
  on 
  the 
  waters 
  of 
  the 
  Eio 
  Grande. 
  

  

  Arrived 
  at 
  this 
  point, 
  we 
  again 
  connect 
  our 
  work 
  with 
  that 
  of 
  1874. 
  

   The 
  great 
  volcanic 
  area 
  continues 
  westward, 
  retaining 
  for 
  the 
  lower 
  

   member 
  of 
  its 
  stratigraphical 
  series 
  the 
  peculiarities 
  of 
  composition 
  

   and 
  occurrence 
  that 
  we 
  have 
  noted 
  in 
  the 
  Lower 
  Sawatch 
  Eange. 
  Higher 
  

   strata 
  occur 
  there, 
  however, 
  that 
  are 
  wanting 
  in 
  our 
  district, 
  and 
  it 
  is 
  

   they 
  that 
  there 
  produce 
  the 
  volcanic 
  peaks 
  reaching 
  an 
  elevation 
  of 
  14,000 
  

   feet 
  and 
  more. 
  Taking 
  an 
  average 
  of 
  the 
  elevations 
  of 
  the 
  higher 
  and 
  

   highest 
  peaks 
  in 
  the 
  district, 
  it 
  will 
  be 
  observed 
  that 
  the 
  absolute 
  

   altitude 
  of 
  their 
  strata 
  corresponds 
  very 
  well 
  with 
  that 
  of 
  the 
  analogous 
  

   beds 
  to 
  the 
  west. 
  This 
  indicates 
  that, 
  although 
  the 
  dip 
  to 
  the 
  eastward 
  

   may 
  be 
  constant, 
  hypsometric 
  variations 
  in 
  the 
  strata, 
  from 
  north 
  to 
  

   south, 
  are 
  almost 
  entirely, 
  if 
  not 
  entirely, 
  wanting, 
  save 
  as 
  very 
  local 
  

   occurrences. 
  

  

  DRIFT. 
  

  

  Mention 
  has 
  been 
  made 
  above 
  of 
  the 
  morainal 
  drift 
  in 
  the 
  upper 
  

   valley 
  of 
  the 
  Chama, 
  and 
  of 
  its 
  probable 
  occurrence 
  in 
  the 
  valley 
  of 
  

   Eio 
  Navajo. 
  The 
  erratic 
  bowlders 
  deposited 
  near 
  station 
  94 
  might 
  be 
  

   counted 
  to 
  this 
  class, 
  but 
  the 
  area 
  covered 
  by 
  them 
  is 
  very 
  small, 
  and 
  

   the 
  accumulations 
  but 
  local. 
  In 
  Appendix 
  A 
  all 
  the 
  glacial 
  evidence 
  

   and 
  deposits 
  are 
  discussed 
  at 
  greater 
  length 
  ; 
  therefore 
  the 
  mere 
  notice 
  

   of 
  the 
  same 
  may 
  here 
  sufiQce. 
  

  

  Eiver-drift, 
  and 
  that 
  class 
  that 
  we 
  are 
  accustomed 
  to 
  term 
  " 
  ava- 
  

   lanchial," 
  occur 
  quite 
  frequently. 
  They 
  are 
  found 
  all 
  along 
  the 
  western 
  

   base 
  of 
  the 
  Sawatch 
  Eange, 
  where 
  they 
  often 
  cover 
  considerable 
  areas. 
  

   The 
  bowlders 
  and 
  fragments 
  have 
  either 
  rolled 
  down 
  from 
  the 
  mountains, 
  

   or 
  have 
  been 
  washed 
  down. 
  Bluffs 
  sometimes 
  several 
  hundred 
  feet 
  in 
  

   height 
  are 
  formed 
  by 
  them, 
  running 
  parallel 
  to 
  the 
  courses 
  of 
  the 
  streams. 
  

   On 
  the 
  streams 
  proper, 
  alluvial 
  soil 
  has 
  accumulated, 
  which, 
  on 
  the 
  Eio 
  

   Grande, 
  is 
  utilized 
  for 
  agricultural 
  purposes. 
  

  

  On 
  the 
  Eio 
  Grande 
  the 
  same 
  phenomena 
  may 
  be 
  observed. 
  Along 
  

   the 
  edges 
  of 
  the 
  mountains 
  bordering 
  upon 
  the 
  river 
  the 
  avalanchial 
  

   drift 
  predominates, 
  while 
  lower 
  down 
  the 
  rounded 
  bowlders 
  and 
  alluvial 
  

   soil 
  set 
  in. 
  It 
  is 
  a 
  matter 
  of 
  interest 
  to 
  observe 
  the 
  distances 
  that 
  such 
  

   redeposited 
  material 
  is 
  often 
  transported. 
  This 
  may, 
  perhaps, 
  best 
  be 
  

   studied 
  on 
  the 
  Eio 
  Grande, 
  where 
  the 
  metamorphic 
  groups 
  near 
  its 
  

   headwaters 
  are 
  represented 
  nearly 
  100 
  miles 
  lower 
  down 
  on 
  the 
  river. 
  

   Bordering 
  on 
  the 
  east 
  side 
  of 
  the 
  Sawatch 
  Eange 
  is 
  San 
  Luis 
  Valley, 
  

   with 
  its 
  almost 
  endless 
  drift. 
  This 
  extends 
  up 
  on 
  the 
  easterly 
  flowing 
  

   rivers 
  to 
  some 
  extent, 
  and 
  fills 
  in 
  the 
  small 
  valleys 
  between 
  the 
  isolated 
  

   bluffs 
  that 
  lie 
  at 
  the 
  eastern 
  edge 
  of 
  the 
  mountains. 
  This 
  is 
  represented 
  

   in 
  the 
  first 
  illustration 
  given 
  in 
  this 
  chapter. 
  San 
  Luis 
  drift 
  proper 
  

   has 
  been 
  treated 
  of 
  in 
  Chapter 
  II, 
  and 
  it 
  is 
  therefore 
  unnecessary 
  to 
  

   repeat 
  a 
  description 
  of 
  those 
  portions 
  lying 
  contiguous 
  to 
  the 
  edge 
  of 
  

   the 
  mountains. 
  

  

  * 
  Report 
  United 
  States 
  Geological 
  Survey 
  1874, 
  page 
  200. 
  

  

  