﻿ENDLICH.J 
  SAWATCH 
  RANGE 
  SAN 
  JUAN 
  DRAINAGE. 
  167 
  

  

  allel 
  to 
  (lateral) 
  the 
  trend 
  of 
  the 
  valley 
  or 
  across 
  it 
  (terminal). 
  The 
  

   present 
  creek-bed 
  indicates 
  the 
  course 
  taken 
  by 
  the 
  ice. 
  On 
  either 
  side 
  

   the 
  soft 
  conglomerates 
  are 
  cut 
  away 
  frequently 
  to 
  a 
  greater 
  extent 
  than 
  

   the 
  overlying 
  trachyte, 
  which 
  in 
  that 
  case 
  broke 
  off 
  and 
  fell 
  down 
  into 
  

   the 
  valley. 
  On 
  the 
  east 
  side, 
  the 
  bluffy 
  wall 
  is 
  the 
  terminus 
  of 
  the 
  pla- 
  

   teau 
  of 
  station 
  88, 
  and 
  from 
  there 
  basalt 
  bowlders 
  have 
  fallen 
  down. 
  

   For 
  a 
  distance 
  of 
  nearly 
  ten 
  miles 
  the 
  glacier 
  must 
  have 
  filled 
  the 
  valley, 
  

   as 
  shown 
  by 
  the 
  morainal 
  deposits 
  and 
  the 
  characteristic 
  carving 
  of 
  the 
  

   rocks 
  inpositu. 
  Below 
  this 
  the 
  stream 
  flows 
  in 
  the 
  trachytic 
  beds 
  until 
  

   it 
  enters 
  the 
  Lower 
  Oretaceous 
  near 
  the 
  mouth 
  of 
  the 
  canon. 
  On 
  the 
  

   plateau 
  containing 
  the 
  most 
  prominent 
  striation 
  and 
  grooving 
  a 
  number 
  

   of 
  " 
  drops 
  " 
  have 
  occurred, 
  which 
  change 
  the 
  normal 
  dip 
  of 
  the 
  strata 
  

   and 
  the 
  direction 
  of 
  the 
  striation. 
  They 
  are 
  found 
  along 
  a 
  line 
  running 
  

   north 
  to 
  south, 
  and 
  measure 
  400 
  to 
  500 
  feet 
  in 
  vertical 
  extent. 
  Either 
  

   none 
  or 
  very 
  little 
  lateral 
  movement 
  was 
  connected 
  with 
  the 
  vertical 
  

   subsidence, 
  still 
  it 
  is 
  sufficient 
  to 
  change 
  the 
  course 
  of 
  the 
  strise. 
  Prob- 
  

   ably 
  the 
  " 
  drops" 
  were 
  produced 
  by 
  an 
  erosion 
  of 
  the 
  underlying 
  con- 
  

   glomerates. 
  They, 
  yielding 
  readily 
  to 
  the 
  action 
  both 
  of 
  water 
  and 
  ice, 
  

   were 
  excavated 
  toward 
  the 
  heads 
  of 
  the 
  canons, 
  and 
  the 
  superincumbent 
  

   trachytes 
  fell 
  down 
  vertically 
  into 
  the 
  cavities 
  thus 
  produced. 
  On 
  the 
  

   east 
  side 
  of 
  the 
  Ohama 
  canon 
  the 
  wall 
  furnished 
  a 
  very 
  good 
  section 
  of 
  

   the 
  volcanic 
  beds 
  of 
  that 
  region. 
  It 
  is 
  about 
  2,500 
  feet 
  high. 
  Near 
  its 
  

   base 
  a 
  talus 
  composed 
  of 
  debris 
  obscures 
  the 
  lowest 
  strata, 
  which 
  are 
  prob- 
  

   ably 
  a 
  brown 
  trachyte. 
  Above 
  them 
  the 
  conglomerates 
  set 
  in, 
  600 
  to 
  800 
  

   feet 
  in 
  thickness, 
  varying 
  on 
  account 
  of 
  having 
  been 
  deposited 
  on 
  a 
  corru- 
  

   gated 
  surface. 
  Higher 
  up 
  we 
  find 
  a 
  bed 
  of 
  massive 
  trachyte, 
  reddish- 
  

   brown 
  in 
  color 
  when 
  fresh, 
  but 
  weathering 
  dark 
  brown. 
  Bands 
  and 
  nod- 
  

   ules 
  of 
  black 
  porphyritic 
  pitch-stone 
  occur 
  higher 
  up, 
  among 
  a 
  series 
  

   of 
  thin 
  trachyte 
  beds 
  that 
  show 
  a 
  banded 
  appearance. 
  This 
  is 
  produced 
  

   by 
  differences 
  in 
  the 
  color, 
  a 
  number 
  of 
  very 
  light 
  beds 
  setting 
  in, 
  which 
  

   then 
  contrast 
  with 
  the 
  darker 
  ones. 
  A 
  high 
  mountain 
  to 
  the 
  northwest 
  

   of 
  this 
  locality 
  has 
  received 
  the 
  name 
  of 
  "Banded 
  Peak," 
  in 
  consequence 
  

   of 
  a 
  similar 
  occurrence. 
  Above 
  these 
  beds, 
  that 
  have 
  altogether 
  a 
  thick- 
  

   ness 
  of 
  about 
  800 
  feet, 
  we 
  find 
  the 
  black 
  basalt 
  of 
  station 
  88. 
  This 
  

   measures 
  200 
  to 
  250 
  feet 
  in 
  thickness. 
  It 
  is 
  vesicular 
  in 
  part, 
  partly 
  

   compact. 
  Decomposition 
  of 
  the 
  magnetite 
  contained 
  therein 
  has 
  pro- 
  

   duced 
  the 
  red 
  variety 
  that 
  so 
  frequently 
  occurs 
  at 
  many 
  other 
  places. 
  

   The 
  Brazos 
  heads 
  in 
  trachyte, 
  but, 
  leaving 
  it, 
  follows 
  the 
  outcrop 
  of 
  the 
  

   metamorphic 
  rocks, 
  which 
  there 
  takes 
  place 
  in 
  the 
  depressions 
  of 
  the 
  

   range. 
  It 
  passes 
  through 
  the 
  steep 
  quartzitic 
  canon 
  south 
  of 
  station 
  94, 
  

   and 
  joins 
  the 
  Ohama 
  in 
  the 
  Cretaceous 
  valley 
  at 
  the 
  base 
  of 
  the 
  mount- 
  

   ains. 
  

  

  Besides 
  the 
  streams 
  above 
  enumerated, 
  we 
  have 
  to 
  consider 
  those 
  

   heading 
  in 
  the 
  Sawatch 
  Eange 
  and 
  flowing 
  into 
  the 
  San 
  Juan, 
  those 
  on 
  

   the 
  western 
  slope 
  of 
  the 
  continental 
  divide. 
  

  

  B. 
  — 
  SAN 
  JUAN 
  DRAINAGE. 
  

  

  Following 
  along 
  the 
  western 
  edge 
  of 
  the 
  Sawatch 
  Eange, 
  in 
  a 
  north- 
  

   westerly 
  direction, 
  we 
  first 
  cross 
  the 
  Eio 
  Navajo. 
  This 
  stream 
  heads 
  

   northwest 
  of 
  station 
  87, 
  and 
  flows 
  south 
  as 
  long 
  as 
  it 
  remains 
  in 
  the 
  

   mountains, 
  turning 
  westward 
  after 
  leaving 
  them. 
  A 
  portion 
  of 
  its 
  

   headwaters 
  rise 
  in 
  the 
  glacial 
  area 
  of 
  the 
  Conejos 
  glacier. 
  It 
  is 
  prob- 
  

   able, 
  although 
  the 
  locality 
  was 
  not 
  personally 
  visited, 
  so 
  as 
  to 
  decide 
  

   positively, 
  that 
  the 
  ice 
  extended 
  down 
  into 
  the 
  narrow 
  valley 
  of 
  the 
  

   Navajo. 
  Ou 
  the 
  west 
  side 
  this 
  valley 
  is 
  separated 
  from 
  the 
  low 
  country 
  

  

  