﻿CHAPTEE 
  VI. 
  

  

  STRATIGEAPHY— 
  MESOZOIO 
  FORMATIONS. 
  

   The 
  mesozoic 
  formations 
  of 
  our 
  district 
  are 
  divided 
  about 
  as 
  follows 
  : 
  

  

  Triassic 
  300 
  to 
  1,600 
  

  

  Jurassic 
  '- 
  300 
  to 
  800 
  

  

  Cretaceous 
  - 
  1,000 
  to 
  2,000 
  

  

  1,600 
  to 
  4,400 
  

  

  The 
  entire 
  thickness 
  of 
  the 
  Cretaceous 
  does 
  not 
  appear 
  in 
  the 
  district, 
  

   and 
  in 
  regard 
  to 
  the 
  Triassic 
  in 
  the 
  Unaweep 
  Canon 
  there 
  is 
  a 
  gradual 
  

   thinning 
  of 
  the 
  beds 
  towards 
  the 
  eastward, 
  

  

  TRIASSIC. 
  

  

  No 
  data 
  were 
  obtained 
  from 
  which 
  anything 
  new 
  can 
  be 
  predicated 
  

   in 
  regard 
  to 
  the 
  series 
  of 
  red 
  beds 
  which 
  we 
  have 
  been 
  in 
  the 
  habit 
  of 
  

   referring 
  to 
  the 
  Triassic. 
  The 
  reasons 
  for 
  such 
  reference 
  have 
  been 
  given 
  

   iti 
  the 
  preceding 
  reports 
  upon 
  Colorado. 
  The 
  general 
  character 
  of 
  the 
  

   beds 
  is 
  as 
  follows: 
  A 
  massive 
  yellow, 
  white, 
  or 
  pink 
  sandstx)ne 
  forms 
  

   the 
  top 
  of 
  the 
  series. 
  Toward 
  the 
  western 
  part 
  of 
  our 
  district 
  this 
  

   sandstone 
  is 
  calcareous. 
  In 
  many 
  places 
  the 
  sandstones 
  are 
  markedly 
  

   cross-stratified. 
  The 
  color 
  is 
  subject 
  to 
  much 
  change 
  locally, 
  passing 
  

   from 
  white, 
  through 
  orange 
  and 
  pink, 
  into 
  deep 
  red. 
  Below 
  the 
  massive 
  

   sandstone 
  are 
  blood-red 
  shales, 
  followed 
  in 
  most 
  by 
  massive 
  brick-red 
  

   sandstone 
  places. 
  In 
  Unaweep 
  Canon 
  the 
  sandstones 
  are 
  laminated, 
  

   while 
  northward 
  and 
  westward 
  they 
  seem 
  to 
  be 
  consolidated 
  into 
  one 
  

   massive 
  bed. 
  They 
  are 
  followed, 
  as 
  we 
  descend 
  in 
  the 
  series, 
  by 
  shales 
  

   and 
  blood-red 
  sandstones, 
  which, 
  on 
  the 
  Dolores, 
  change 
  gradually 
  into 
  

   gypsiferous 
  shales 
  and 
  sandstones. 
  The 
  latter 
  I 
  have 
  considered 
  as 
  

   belonging 
  to 
  the 
  Permian. 
  It 
  is 
  difficult 
  to 
  draw 
  any 
  line 
  between 
  the 
  

   Trias 
  and 
  the 
  Permian, 
  and 
  I 
  have 
  been 
  obliged 
  to 
  do 
  so 
  arbitrarily. 
  

  

  The 
  Triassic 
  rocks 
  ^.re 
  the 
  surface 
  formation 
  over 
  about 
  600 
  square 
  

   miles 
  of 
  the 
  district, 
  while 
  Carboniferous 
  rocks 
  form 
  the 
  surface 
  over 
  

   only 
  60 
  square 
  miles.' 
  The 
  area 
  in 
  which 
  Triassic 
  rocks 
  are 
  present 
  

   beneath 
  the 
  overlying 
  Cretaceous 
  formations 
  is 
  very 
  much 
  larger 
  than 
  

   that 
  in 
  which 
  we 
  have 
  reason 
  to 
  suspect 
  the 
  presence 
  of 
  Paleozoic 
  forma- 
  

   tions 
  beneath 
  the 
  Trias. 
  At 
  the 
  end 
  of 
  the 
  Carboniferous 
  period, 
  the 
  

   subsidence 
  of 
  the 
  land 
  appears 
  to 
  have 
  allowed 
  the 
  sea 
  to 
  spread 
  over 
  

   much 
  wider 
  areas, 
  and 
  it 
  seems 
  that 
  the 
  sea 
  encroached 
  on 
  the 
  land 
  

   gradually, 
  as 
  the 
  Triassic 
  period 
  advanced, 
  until 
  it 
  covered 
  almost 
  all 
  of 
  

   it. 
  We 
  see 
  that 
  in 
  all 
  parts 
  of 
  our 
  district 
  the 
  upper 
  portion 
  of 
  the 
  

   series 
  presents 
  the 
  same 
  character, 
  and 
  as 
  I 
  shall 
  show 
  in 
  a 
  subsequent 
  

   portion 
  of 
  the 
  chapter, 
  agrees 
  closely 
  with 
  the 
  upper 
  part 
  of 
  the 
  series 
  

   at 
  other 
  localities 
  in 
  Colorado, 
  and 
  in 
  Utah, 
  and 
  New 
  Mexico. 
  The 
  

   conditions, 
  therefore, 
  that 
  existed 
  in 
  our 
  district 
  during 
  its 
  formation 
  

   were 
  present 
  over 
  a 
  wide 
  area. 
  It 
  is 
  impossible 
  to 
  define 
  the 
  area 
  in 
  

  

  80 
  

  

  