THE   CORDILLERAS.  853 
SECTION  9.     MONTANA. 
SUMMARY    OF   LITERATURE. 
Hayden,111  in  1861,  describes,  along  the  Madison,  one  of  the  forks 
of  the  Missouri,  beds  of  feldspathic  rocks  and  mica  slates  and  clay 
slates  above  the  eruptive  granites  of  the  region. 
Hayden,43  in  1872,  describes  Archean  rocks  at  many  points  in 
southwestern  Montana.  Among  the  localities  mentioned  the  follow- 
ing are  worthy  of  note :  On  Black-Tailed  Deer  Creek,  in  southwest- 
ern Montana,  is  an  immense  thickness  of  alternating  beds  of  quartz- 
ites,  true  gneiss,  and  mica  schist,  the  first  predominating,  and  inclin- 
ing to  the  west  from  30°  to  45°.  Old  granite  ridges  are  also  found. 
On  the  north  side  of  this  creek  are  gneissic  beds,  which  incline  to  the 
northwest  at  angles  varying  from  30°  to  60°.  On  the  Stinking  Water 
are  immense  thicknesses  of  micaceous  gneiss  underlying  massive 
layers  of  quartzite.  Along  Madison  Canyon  is  found  granite.  The 
rocks  adjacent  to  Virginia  City  are  clearly  stratified,  wholly  meta- 
morphic,  and  are  regarded  as  below  the  Paleozoic.  On  the  Upper 
Gallatin  are  granitic  nuclei,  with  the  unchanged  sedimentary  beds 
upon  the  sides  and  summits  inclining  at  various  angles.  In  the  first 
canyon  of  the  Yellowstone  are  true  gneissoid  granite  and  micaceous 
gneiss  of  different  shades  of  color,  giving  its  sides  a  peculiarly  strati- 
fied appearance.  At  Cinnabar  Mountain  is  a  plainly  metamorphic, 
reddish,  feldspathic  quartzite,  upon  which  rests  unconformably  the 
Carboniferous  limestone.  Hell-Roaring  Mountain  consists  of  strati- 
fied gneiss  and  massive  red  or  gray  feldspathic  granite.  At 
Horse  Plain  Valley  are  quartzites  and  micaceous  schists,  which  rise 
beneath  the  limestones  and  quartzites  of  Carboniferous  age. 
Peale,138  in  1872,  gives  many  details  with  reference  to  the  litho- 
logical  and  mineralogical  character  of  the  rocks,  the  locations  of  which 
are  given  by  Hayden. 
Hayden,45  in  1873,  gives  many  additional  facts  with  reference  to 
the  occurrence  of  Archean  rocks  in  southwestern  Montana  and  ad- 
jacent regions.  The  mountain  range  east  of  the  Yellowstone,  sup- 
posed to  be  mostly  of  igneous  origin,  has  the  characteristic  granitic 
nucleus  common  to  the  mountain  ranges  of  the  region.  In  ascending 
the  lower  canyon  of  the  Yellowstone  the  first  ridge  is  composed 
mostly  of  metamorphic  quartzite,  the  second  of  mica  schists  and 
granitoid  gneiss.  The  ribboning  and  banding  of  the  gneiss  is  quite 
remarkable  for  its  perfection  and  regularity.  Granitic  rocks  consti- 
tute the  nucleus  of  the  Yellowstone  Range  and  make  up  a  rugged 
granite  range  east  of  Clarks  Fork.  At  Henry  Lake  and  Tahgee  Pass 
(he  quartzites  and  gneissic  rocks  appear  beneath  the  limestones.  The 
lower  portion  of  the  unchanged  rocks  are  pebbly  arenaceous  sand- 
stones and  limestones  containing  pebbles  which  are  much  worn  and 
