﻿68 
  EEPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  derived 
  ? 
  We 
  have 
  no 
  data 
  from 
  which 
  we 
  are 
  able 
  even 
  to 
  guess 
  

   what 
  was 
  the 
  extent 
  of 
  the 
  Archaean 
  continent, 
  or 
  what 
  its 
  character 
  

   was.' 
  

  

  Speaking 
  of 
  the 
  granite 
  in 
  the 
  Grand 
  Canon 
  of 
  the 
  Colorado 
  Eiver, 
  

   Professor 
  Newberry* 
  says 
  : 
  

  

  The 
  granite 
  forming 
  the 
  base 
  of 
  the 
  series 
  is 
  very 
  compact 
  and 
  massive, 
  scarcely 
  showing 
  

   any 
  tendency 
  to 
  stratification. 
  It 
  is 
  cut 
  by 
  veins 
  of 
  quartz 
  of 
  large 
  size, 
  and 
  contains 
  veins 
  

   of 
  handsome 
  red 
  syenite 
  and 
  coarse 
  red 
  feldspathic 
  granite, 
  with 
  plates 
  of 
  silvery 
  mica. 
  All 
  

   these 
  seem 
  to 
  have 
  been 
  injected 
  into 
  fissures. 
  The 
  erosion 
  of 
  the 
  canon 
  has 
  beautifully 
  

   displayed 
  the 
  ancient 
  surface 
  of 
  the 
  granite, 
  and 
  shows 
  it 
  to 
  have 
  been 
  extremely 
  irregular 
  ; 
  

   hills 
  several 
  hundred 
  feet 
  high, 
  many 
  of 
  which 
  have 
  precipitous 
  sides 
  and 
  deserve 
  the 
  name 
  

   of 
  pinnacles, 
  have 
  been 
  exhumed 
  from 
  the 
  sediments 
  in 
  which 
  they 
  were 
  enveloped. 
  The 
  

   sandstones 
  and 
  shales 
  (Potsdam) 
  are 
  seen 
  to 
  have 
  been 
  deposited 
  quietly 
  around 
  them, 
  their 
  

   strata, 
  nearly 
  horizontal, 
  abutting 
  against 
  their 
  sides. 
  We 
  have 
  here 
  evidence 
  that 
  at 
  least 
  

   these 
  granite 
  hills 
  are 
  older 
  than 
  any 
  of 
  the 
  stratified 
  rocks 
  of 
  the 
  table-lands. 
  

  

  The 
  description 
  of 
  the 
  granite 
  rocks 
  is 
  not 
  dissimilar 
  to 
  that 
  which 
  

   might 
  be 
  given 
  of 
  those 
  in 
  the 
  XJnaweep 
  Canon. 
  Major 
  Powell,t 
  speak- 
  

   ing 
  of 
  the 
  crystalline 
  schists 
  of 
  the 
  Grand 
  Canon 
  of 
  the 
  Colorado, 
  says 
  : 
  

  

  We 
  find 
  these 
  lower 
  rocks 
  to 
  be 
  composed 
  chiefly 
  of 
  metamorphosed 
  sandstones 
  and 
  

   shales, 
  which 
  have 
  been 
  folded 
  so 
  many 
  times, 
  squeezed, 
  and 
  heated, 
  that 
  their 
  original 
  

   structure, 
  as 
  sandstones 
  and 
  shales, 
  is 
  greatly 
  obscured 
  or 
  entirely 
  destroyed, 
  so 
  that 
  they 
  

   are 
  called 
  metamorphic 
  crystalline 
  schists. 
  

  

  After 
  these 
  beds 
  were 
  deposited, 
  after 
  they 
  were 
  folded, 
  and 
  still 
  after 
  they 
  were 
  deeply 
  

   eroded, 
  they 
  were 
  fractured, 
  and 
  through 
  the 
  fissures 
  came 
  floods 
  of 
  molten 
  granite, 
  which 
  

   now 
  stands 
  in 
  dikes, 
  or 
  lies 
  in 
  beds, 
  and 
  the 
  metamorphosed 
  sandstones 
  and 
  shales 
  and 
  the 
  

   beds 
  of 
  granite 
  present 
  evidences 
  of 
  erosion 
  subsequent 
  to 
  the 
  periods 
  just 
  mentioned, 
  yet 
  

   antecedent 
  to 
  the 
  deposition 
  of 
  the 
  non-conformable 
  sandstones. 
  {Sandstones 
  below 
  the 
  

   Carboniferous, 
  and 
  unconformable 
  to 
  the 
  latter.) 
  

  

  From 
  both 
  these 
  extracts 
  we 
  see 
  that 
  the 
  Archsean 
  rocks 
  upon 
  which 
  

   the 
  Potsdam 
  sandstone 
  was 
  deposited 
  present 
  evidences 
  of 
  erosion 
  pre- 
  

   vious 
  to 
  their 
  deposition. 
  The 
  material 
  thus 
  carried 
  away 
  must 
  have 
  

   contributed 
  to 
  the 
  formation 
  of 
  strata 
  older 
  than 
  the 
  Potsdam 
  sand- 
  

   stone. 
  May 
  not 
  the 
  schists 
  already 
  noted 
  be 
  a 
  portion 
  of 
  the 
  strata 
  

   thus 
  formed 
  ? 
  I 
  have 
  referred 
  to 
  the 
  probability 
  of 
  their 
  being 
  of 
  later 
  

   origin 
  than 
  the 
  Archaean 
  rocks 
  of 
  Unaweep 
  (Jauon. 
  We 
  would 
  then 
  

   have 
  to 
  assume 
  that 
  the 
  rocks 
  of 
  the 
  caQon 
  and 
  those 
  beneath 
  the 
  Pots- 
  

   dam 
  sandstones 
  in 
  the 
  Canon 
  of 
  the 
  Colorado 
  are 
  of 
  the 
  same 
  age. 
  We 
  

   would 
  have 
  to 
  assume, 
  also, 
  two 
  elevations 
  precedent 
  to 
  the 
  formation 
  

   of 
  any 
  Silurian 
  layers. 
  The 
  first 
  elevation 
  would 
  be 
  that 
  of 
  the 
  granite 
  

   area. 
  Then 
  would 
  follow 
  a 
  period 
  of 
  erosion, 
  indicated 
  by 
  the 
  irregu- 
  

   lar 
  surface 
  noted 
  by 
  Newberry, 
  cutting 
  the 
  granite 
  into 
  hills. 
  We 
  will 
  

   suppose 
  the 
  material 
  derived 
  from 
  this 
  erosion 
  to 
  be 
  deposited 
  at 
  the 
  

   bottom 
  of 
  the 
  ancient 
  sea, 
  forming 
  the 
  beds 
  which 
  afterward 
  were 
  

   metamorphosed 
  into 
  the 
  schists, 
  an 
  outcrop 
  of 
  which 
  we 
  are 
  supposed 
  

   to 
  have 
  seen 
  near 
  the 
  Grand 
  Eiver, 
  with 
  a 
  dip 
  to 
  the 
  northeast 
  at 
  an 
  

   angle 
  of 
  60°. 
  But 
  why 
  should 
  the 
  granite 
  of 
  Unaweep 
  Caiiou 
  show 
  so 
  

   regular 
  a 
  surface 
  as 
  we 
  note 
  beneath 
  the 
  red 
  beds 
  resting 
  on 
  it 
  there 
  ? 
  

   It 
  may 
  have 
  been 
  near 
  the 
  shore 
  of 
  the 
  sea, 
  and 
  therefore 
  less 
  liable 
  to 
  

   erosion 
  than 
  the 
  country 
  farther 
  west, 
  which 
  was 
  probably 
  higher, 
  or 
  it 
  

   may 
  mark 
  a 
  portion 
  of 
  the 
  bottom 
  of 
  the 
  sea, 
  on 
  which 
  the 
  schists 
  were 
  

   deposited 
  aud 
  afterward 
  removed. 
  Next 
  we 
  have 
  a 
  depression 
  of 
  the 
  

   granitic 
  area 
  in 
  the 
  region 
  of 
  the 
  Colorado. 
  Contemporaneous 
  with 
  this 
  

   there 
  may 
  have 
  been 
  an 
  elevation 
  in 
  our 
  district, 
  for, 
  although 
  on 
  the 
  

   Colorado 
  we 
  find 
  the 
  Postdam 
  sandstones 
  deposited 
  in 
  the 
  irregularities 
  

   of 
  the 
  granite, 
  here 
  we 
  find 
  no 
  stratified 
  beds 
  deposited 
  on 
  it 
  until 
  a 
  later 
  

   l)eriod. 
  This 
  elevation 
  would 
  account 
  for 
  the 
  tipping 
  up 
  of 
  the 
  schists, 
  a 
  

  

  *Report 
  Ives's 
  Colorado 
  Exploring 
  Expedition, 
  

   t 
  Exploration 
  of 
  the 
  Colorado 
  River 
  of 
  the 
  West. 
  

  

  