﻿HOLMES] 
  LOWER 
  CRETACEOUS 
  FORMATIONS. 
  263 
  

  

  mountains. 
  It 
  is 
  in 
  cutting 
  through 
  this 
  arch 
  that 
  the 
  red 
  beds 
  are 
  ex- 
  

   posed. 
  

  

  The 
  section 
  made 
  here 
  is 
  almost 
  identical 
  with 
  that 
  made 
  on 
  the 
  San 
  

   Juan 
  near 
  Station 
  45. 
  The 
  Upper 
  Dakota 
  Group 
  seems 
  somewhat 
  more 
  

   fully 
  developed, 
  showing 
  upward 
  of 
  200 
  feet 
  of 
  sandstones 
  in 
  the 
  bluff 
  

   face. 
  The 
  Lower 
  Dakota 
  Group 
  shows 
  considerably 
  more 
  sandstone 
  

   and 
  there 
  is 
  much 
  more 
  persistency 
  in 
  individual 
  beds. 
  The 
  red 
  and 
  

   pink 
  sandstones 
  are 
  very 
  massive. 
  They 
  outcrop 
  for 
  two 
  or 
  three 
  miles 
  

   along 
  the 
  river, 
  and 
  on 
  the 
  north 
  side 
  of 
  the 
  vallej^, 
  opposite 
  Ute 
  Moun- 
  

   tain, 
  sweep 
  back 
  in 
  a 
  great 
  amphitheater. 
  In 
  the 
  more 
  massive 
  beds 
  

   there 
  are 
  weathered 
  many 
  deep 
  caves 
  in 
  which 
  the 
  ancient 
  inhabitants 
  

   have 
  built 
  their 
  rock 
  shelters. 
  On 
  the 
  lower 
  McElmo 
  there 
  are 
  expo- 
  

   sures 
  of 
  Lower 
  Cretaceous 
  rocks 
  only. 
  

  

  Between 
  the 
  McBlmo 
  and 
  Hovenweep, 
  in 
  that 
  part 
  traversed 
  by 
  the 
  

   trail 
  to 
  Hovenweep 
  Castle, 
  there 
  is 
  a 
  large 
  area 
  from 
  which 
  the 
  Upper 
  

   Dakota 
  sandstones 
  have 
  been 
  more 
  or 
  less 
  completely 
  removed. 
  Here 
  

   the 
  harder 
  layers 
  of 
  the 
  variegated 
  group 
  beneath 
  are 
  broken 
  up 
  into 
  

   numberless 
  little 
  blocks, 
  which 
  are 
  covered 
  with 
  a 
  black, 
  lustrous 
  coat- 
  

   ing 
  of 
  some 
  mineral 
  that 
  makes 
  them 
  look 
  like 
  iron-ore. 
  The 
  coating 
  

   is 
  very 
  thin, 
  and 
  is 
  probably 
  black 
  oxide 
  of 
  manganese. 
  I 
  have 
  observed 
  

   the 
  same 
  phenomenon 
  in 
  other 
  localities, 
  notably 
  in 
  New 
  Mexico, 
  

   between 
  El 
  Rito 
  and 
  Abiquiu. 
  Dr. 
  Loew, 
  on 
  page 
  1020, 
  Report 
  of 
  the 
  

   Chief 
  of 
  Engineers 
  for 
  1875, 
  gives 
  an 
  analysis 
  of 
  the 
  same 
  material. 
  

  

  The 
  Montezuma 
  occupies 
  a 
  system 
  of 
  caiions 
  somewhat 
  more 
  compli- 
  

   cated 
  and 
  considerably 
  more 
  extensive 
  than 
  the 
  McElmo. 
  The 
  upper 
  

   branches 
  reach 
  far 
  out 
  to 
  the 
  north, 
  ramifying 
  the 
  Great 
  Sage-Plain 
  in 
  

   a. 
  most 
  remarkable 
  manner. 
  From 
  Ute 
  Peak 
  on 
  the 
  east 
  I 
  looked 
  out 
  

   over 
  this 
  desolate 
  region, 
  and 
  afterward 
  from 
  the 
  Abajo 
  on 
  the 
  west, 
  

   but 
  the 
  network 
  of 
  caiions 
  was 
  quite 
  unintelligible. 
  Gorges 
  and 
  broken 
  

   precipices 
  and 
  Impassable 
  walls 
  of 
  rock 
  followed 
  each 
  other 
  in 
  such 
  

   quick 
  succession 
  that 
  no 
  portion 
  of 
  the 
  plain 
  country 
  seemed 
  to 
  be 
  left. 
  

   Sa 
  far 
  as 
  I 
  could 
  learn 
  there 
  is 
  no 
  running 
  water 
  during 
  the 
  summer 
  ex- 
  

   cepting 
  near 
  the 
  east 
  base 
  of 
  the 
  Abajo 
  Mountains 
  ; 
  but 
  the 
  growth 
  of 
  

   cottonwoods, 
  willows, 
  and 
  grass 
  along 
  the 
  lower 
  course 
  indicates 
  that 
  

   there 
  is 
  considerable 
  moisture 
  most 
  of 
  the 
  year 
  and 
  running 
  water, 
  

   probably, 
  during 
  the 
  winter 
  and 
  spring. 
  The 
  Dakota 
  sandstonfe 
  every- 
  

   where 
  forms 
  the 
  summits 
  of 
  the 
  cliffs 
  and 
  the 
  level 
  tops 
  of 
  the 
  table- 
  

   lands, 
  while 
  the 
  Lower 
  Dakota 
  Group 
  outcrops 
  in 
  the 
  slopes. 
  In 
  the 
  

   West 
  Montezuma 
  caSon, 
  nearly 
  midway, 
  the 
  Red 
  Beds 
  are 
  exposed 
  for 
  a 
  

   short 
  distance, 
  but 
  not 
  to 
  any 
  considerable 
  thickness. 
  The 
  caiion 
  walls 
  

   are 
  ujiward 
  of 
  1,000 
  feet 
  in 
  height. 
  

  

  REaiON 
  OF 
  THE 
  RIO 
  DOLORES. 
  

  

  The 
  Rio 
  Dolores 
  may 
  well 
  be 
  regarded 
  as 
  one 
  of 
  the 
  most 
  interesting 
  

   and 
  remarkable 
  rivers 
  of 
  the 
  Colorado 
  Plateau 
  region, 
  while 
  at 
  the 
  same 
  

   time 
  it 
  is 
  certainly 
  the 
  least 
  known. 
  Having 
  its 
  origin 
  in 
  the 
  San 
  Juan 
  

   Mountains, 
  it 
  flows 
  toward 
  the 
  south 
  and 
  southwest 
  for 
  upward 
  of 
  30 
  

   miles, 
  and 
  then 
  turns 
  abruptly 
  to 
  the 
  northwest 
  and 
  afterward 
  to 
  the 
  

   north, 
  passing 
  to 
  the 
  east 
  of 
  the 
  Abajo 
  and 
  Salt 
  Mountains, 
  and 
  joining 
  

   the 
  Grand 
  in 
  Utah 
  100 
  miles 
  below 
  the 
  south 
  bend. 
  In 
  describing 
  the 
  

   area 
  drained 
  by 
  this 
  stream 
  I 
  shall 
  have 
  to 
  deal 
  principally 
  with 
  the 
  

   sandstones 
  of 
  the 
  Dakota 
  group, 
  as 
  they 
  govern 
  the 
  entire 
  surface 
  ero- 
  

   sion 
  and 
  give 
  shape 
  to 
  all 
  the 
  principal 
  topographic 
  features. 
  On 
  a 
  line 
  

   drawn 
  east 
  and 
  west 
  through 
  Ute 
  Peak 
  to 
  the 
  Montezuma 
  on 
  the 
  west 
  

   and 
  the 
  Rio 
  Mancos 
  on 
  the 
  east, 
  the 
  upper 
  surface 
  of 
  these 
  sandstones 
  

  

  