THE   CORDTLLEEAS.  785 
Archean  rocks  in  the  Cottonwood  area  is  a  mass  of  granite  and 
granite  gneiss.  This  rock  at  Clayton  Peak  possesses  the  physical 
habit  of  a  truly  eruptive  granite  and  has  been  the  center  of  local 
metamorphism,  but  the  evidence  points  to  the  belief  that  it  is  of 
Archean  age.  In  Cottonwood  Canyon  there  is  no  sharp  division 
between  the  structureless  granite  and  the  bedded  gneissoid  form.  In 
the  neighborhood  of  Clayton  Peak  are  bodies  of  granite  porphyry 
which  are  probably  a  dependent  of  the  granite.  West  of  the  granite 
body  of  Little  Cottonwood  Canyon  is  a  belt  of  Archean  schists  and 
quartzites  having  a  thickness  of  2,000  or  3,000  feet  and  dipping  at 
a  high  angle  to  the  northeast.  In  Little  Cottonwood  Canyon  the 
quartzites  are  in  junction  with  the  granite,  while  at  the  mouth  of 
Big  Cottonwood  Canyon,  in  direct  contact  with  the  granite  is  mica 
schist.  Between  the  Archean  granite  and  the  crystalline  schists  there 
are  no  transitions  such  as  to  lead  to  the  belief  that  the  granite  is 
a  more  highly  metamorphic  form  of  the  schist.  The  contact  is  (dearly 
defined,  the  rocks  are  mineralogically  dissimilar,  and  the  granite 
is  either  an  intrusive  mass  or  else  an  original  boss  over  which  the 
Archean  sedimentary  materials  were  deposited.  The  absence  of 
granite  dikes  in  the  schists  strengthens  the  belief  that  the  granite  is 
older.  The  Cambrian  rocks  are  in  such  a  position  as  to  indicate  that 
the  granites  and  schists  alike  antedate  them,  although  in  some  in- 
stances intrusive  dikes  do  cut  the  marbleized  limestone,  but  they  are 
middle-age  porphyries,  not  to  be  confounded  with  the  Archean  crys- 
talline rocks. 
In  the  next  Archean  mass  to  the  north — the  Farmington  area— in 
Sawmill  Canyon,  there  seem  to  be  two  distinct  series.  The  later  series 
consists  of  conformable  beds  of  gneiss,  quartzite,  and  hornblende 
schist,  which  dip  west  at  angles  of  15°  to  40°,  and  rest  unconform- 
ably  upon  an  intensely  metamorphosed  material  composed  of  quartz, 
orthoclase,  and  muscovite.  In  reference  to  the  Farmington  gneisses 
it  is  said:  A  mica  schist  passing  into  a  hornblende  schist,  or  a  horn- 
blende schist  into  a  granite,  or  a  gneiss  rock  into  an  argillite,  along 
the  line  of  their  longitudinal  extensions,  are  phenomena  which  fail  to 
appear  on  the  fortieth  parallel.  The  small  granitoid  body  in  Saw- 
mill Canyon  is  referred  to  the  Laurentian,  while  the  second  serie-  of 
metamorphic  rocks,  comprising  the  gneisses  and  schists,  L2,000  or 
14,000  feet  thick,  are  referred  to  the  Iluronian,  as  are  also  the  a  mil 
lites  of  Salt  Lake  Islands. 
The  Paleozoic  -cries  of  the  Wasatch,  although  30,000  feet  in  thick- 
ness, show  in  their  lowest  portions  only  a  very  -light  tendency  to  be- 
come crystalline  schists.  The  pre-Cambrian  topography  of  the  north- 
ern part  of  the  Wasatch  was  that  of  domelike  peaks  with  gently  in- 
clined  sides.     The  Cottonwood   canyons,  however,  presented   an  al- 
;">721  —P. nil.  .'{GO— 09 50 
