CHAPTEEYI. 
THE  CORDILLERAS. 
SECTION  I.      LARAMIE,  MEDICINE   BOW,  AND  PARK  RANGES  IN  SOUTH 
ERN   WYOMING. 
LITERATURE. 
Stansbury,1  in  1853,  states  that  in  the  Black  hills  (Laramie)  is  ar 
extensive  formation  of  massive  red  feldspatliic  granite  with  occasional 
outcrops  of  ferruginous  quartz.  t 
Hayden,2  in  1863,  describes  the  Laramie  hills  as  consisting  of  nu 
merous  centers  of  uplifted  granite  upon  the  sides  of  which  the  Carbon 
iferous  limestones  are  scattered  or  unconformably  overlie.  There  is 
every  gradation  from  unchanged  fossiliferous  limestone  to  completely 
metamorphosed  rock,  melted  material  sometimes  being  found  thrust  intc 
the  seams  of  the  unchanged  mass.  The  core  of  Laramie  peak  is  o: 
granite,  while,  as  if  thrown  oft*  by  this  nucleus,  is  a  series  of  Azoic  strati 
fled  rocks  consisting  of  gneiss,  hornblendic,  micaceous,  and  talcose 
slates,  syenite,  and  quartz,  which  are  cut  here  and  there  by  dikes  o] 
trap  or  basalt. 
Hayden,3  in  1808,  mentions  granites  and  syenites  as  occurring  in  tin 
Laramie  and  Medicine  bow  ranges.  On  the  east  side  of  Laramie  range 
especially  near  fort  Laramie,  are  seen  the  distinctly  discordant  rela- 
tions between  the  crystalline  rocks  of  the  mountain  range  and  the 
un metamorphosed  strata. 
Hayden,4  in  1872,  describes  on  one  of  the  branches  of  the  Chug 
water,  in  the  Laramie  mountains,  as  occurring  interstratified  with  red 
feldspatliic  granite,  beds  of  magnetic  ore  which  resemble  the  lake  Su- 
perior iron  ores.  The  rocks  between  the  headwaters  of  the  Chugwatei 
and  Laramie  consist  of  beds  of  quartz,  black  gneiss,  seams  pMeldspal 
with  now  and  then  beds  of  massive  granite.  On  approaching  the 
mountains  the  red  feldspatliic  granite  is  found  in  great  ridges,  the 
gneissic  strata  diminishing  and  the  massive  granite  increasing  in  ad 
proaching  the  mountain  range. 
Engelmann,5  in  1876,  finds  that  the  Laramie  peak  system  consists 
of  the  igneous  rocks,  granite  and  granitic  syenite.  Among  the  igneous 
rocks  are  also  greenstones,  which  are  of  later  date  than  the  granite  hi 
which  they  frequently  are  dikes. 
Hague,6  in  1877,  gives  detailed  descriptions  of  the  Laramie,  Medfl 
cine  bow,  and  Park  ranges.  The  Archean  rocks  of  the  Laramie  hills 
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