vanhisb.]  THE    CORDILLERAS.  287 
Hayden,4  in  1872,  states  that  in  the  Uintas,  from  the  red  beds  of  the 
Triassic  to  the  oldest  quartzites  no  unconformity  was  detected.  The 
whole  series  lias  a  thickness  of  10,000  feet  or  more;  of  this  the  lower 
8,000  consists  of  sandstones  and  quartzites.  Although  no  fossils  were 
found,  the  upper  part  of  these  8,000  feet  is  believed  to  be  Silurian  and 
to  pass  down  without  a  break  to  the  rocks  of  the  Huronian  age.  The 
quartzites  are  like  the  Sioux  Mis,  Dakota,  quartzites  which  are  associ- 
ated with  the  pipestone  referred  by  Hall  to  the  Huronian.  In  the 
Uinta  series  is  an  excellent  illustration  of  a  gradual  transition  from 
unchanged  to  metainorphic  rocks. 
Passing  upward  to  the  crest  of  the  mountains,  but  downward  in  a 
geological  sense,  we  find  a  series  of  purplish  sandstones  and  slates, 
conformable  with  the  limestones  and  apparently  unchanged,  which 
gradually  pass  into  thick  beds  of  gray  and  purple  quartzite,  which  are 
exceedingly  brittle  and  plainly  metamorphosed  by  heat.  The  later 
formations  once  passed  over  the  older  ones  in  the  Uintas,  and  therefore 
there  has  been  in  this  region  tremendous  erosive  forces.  On  Bed  creek, 
the  only  place  where  such  a  rock  is  found,  is  the  largest  display  of  white 
quartz  that  the  author  has  seen  in  the  West.  This  is  associated  with 
outbursts  of  old  trap  and  some  beds  of  true  gneiss  and  mica-schist. 
The  igneous  matter  has  protruded  itself  in  every  opening  or  fissure  in 
every  possible  direction,  sometimes  between  the  strata  and  sometimes 
across  them,  in  thin  layers  or  in  huge  branching  masses.  It  is  believed 
that  this  igneous  material  was  protruded  among  the  quartz  beds  prior 
to  their  upheaval.  It  is  difficult  to  account  for  this  development  of  quartz 
with  gneiss,  which  rises  abruptly  above  the  quartzite,  occupying  a  belt 
5  to  9  miles  in  width  and  ending  as  abruptly  as  it  commences.  The 
upper  quartzites  and  white  quartz  beds  seem  to  conform.  It  is  remarked 
that  the  geology  of  the  eastern  portion  of  the  Uinta  range  is  very  com- 
plicated and  interesting,  but  to  have  solved  the  problem  to  entire  sat 
isfaction  would  have  required  a  week  or  two. 
Powell,28  in  1874,  describes  in  the  Uinta  mountains  crystalline 
schists  upon  which  rest  unconformable  Carboniferous  rocks. 
Powell,29  in  1876,  describes  the  Uinta  sandstones,  shales,  and  quartz- 
ites 12,500  feet  thick,  as  resting  un conformably  below  the  Lodore 
group.  Again,  un  conformably  below  the  Uinta  sandstone  is  the  Red 
creek  quartzite  associated  with  hornblendic  and  micaceous  schists, 
10,000  feet  thick.  It  is  evident  that  the  metamorphism  of  the  lied 
creek  quartzite  is  anterior  to  the  deposition  of  the  Uinta  group,  for  the 
beds  of  the  latter,  especially  near  the  junction,  are  chiefly  made  up  of 
fragments  of  the  former;  hence  the  unconformity  is  very  great,  and  the 
quartzite  was  a  lofty  headland  in  the  old  Uinta  sea — perhaps  20,000  feet 
high — when  the  lowest  member  of  the  Uinta  sandstone  was  formed. 
The  period  of  erosion  separating  the  Uinta  sandstones  front  flic  Car- 
boniferous beds  was  sufficient  to  cany  away  at  least  3,000  feet  of  the 
former,  and  how  much  more  can  not  be  said.     This  unconformity  is 
